Delay Wipers

It can be done!
by Mike Rowand
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         Mike Rowand had stumbled on to The Stovebolt Page some time ago as he was "googling" around. Mike is from the Seattle, Washington area and he has a fascinating web site himself, with some really detailed information, which he is regularly updating as he learns new stuff. One of our readers had come across his site -- oddly on a rainy day -- and discovered this great information about windshield wiper pulse delay. Much thanks to Mike for taking the time to put all this together, and for allowing us to add it to our Tech Tips page. And thanks to Alan Horvath for coming up with the great "action photo." If you have questions about the tip, feel free to contact Mike. ~~ Editor

    This page is all about delay wiper systems and how to retrofit them to your vehicle. This may not seem like a big deal to many people, but where I live it doesn't rain as much as you get a heavy fog. It's just enough to need to run the wipers ever few seconds. Leaving the wipers on low without sufficient water on the windshield results in running the wiper blades across a pretty dry windshield - and that leads to annoying squeaks on every swipe of the blades and excessive wear and tear on the wiper system. The squeaks alone will drive you nuts, and pumping the wiper switch on and then off again every few seconds gets old real fast.

    Some background will be helpful here. When I do conversions, I like them to be as if the factory had done them. I don't like extra boxes and switches hanging off the bottom of the dash, and I like things to work correctly. Thus, I spend a lot of time researching changes (like this) to get them functioning correctly, starting from the driver's perspective (what switches and knobs are needed to control things) and working my way back to the wiper motor. This includes such ideas as finding a later model vehicle with a similar dash layout and using the switch and delay box assembly from that vehicle, such as for my 1975 Suburban, 1973 Buick, and 1964 Ranchero. It might also include aftermarket conversions for older vehicles that have aftermarket conversions commonly available that include delay wipers. My 1958 Buick has vacuum operated wipers and I found a drop-in conversions to electric wipers with a delay option from New Port Engineering. As part of this, you might end up changing out your wiper motor to get the desired results. I will have to do this on my '73 Buick and most likely on my '75 Suburban as well. Finally, this might include custom switch and wiring work to get things to work the way you want them to. It all depends on what you have to work with, what you want to end up with, and how far you are willing to go for a seamless / trick / cool setup.

How does it work?

   How do delay wipers work from the driver's point of view? Well, you have an extra setting between "off" and "low" for the delay mode. You will also have a way to select from a range of delay periods. Some vehicles use a fixed number of positions. Others use a simple knob that you can rotate to adjust it.

    Electrically speaking, the system is pretty simple. Each time the wipers need to wipe, they get power for a few seconds and they perform a single sweep at the "low" speed. Typically, the auto-parking feature (the thing that makes the blades always return to the bottom of their travel when you turn off the wipers) ensures that once the blades start to move, that the single sweep is completed. For depressed-park wiper systems, there is also some way to force the blades to return to the bottom of their travel, but not to go all the way into their fully parked position. The time setting between sweeps is controlled by a resistance value based on what the controls are set to by the driver. The circuits used to accomplish this vary. But the tough stuff is contained into a control box of some sort. The box may also be integrated into the switch or motor (or in some cases split between both with some wires in between) on some cars.

How do I convert my vehicle?

Add A Factory Option

    Your first and best choice is to see if your year and model vehicle had delay wipers as an option. If so, figure out what the differences are by going through the factory manuals, and hunt the junkyards, parts stores, or even the dealer for the right parts to make the conversion. You may need a different wiper motor in some cases. Rebuilt units are typically available at the parts store for a reasonable cost. Once you have the parts and the manuals, it should be a simple matter of installing the right switch, motor, and (if needed) wiring. If all goes well, things should all fit like they were meant to and the wipers should work without trauma.

Add A Factory Option From a Later Year

    If your year and model did not have delay wipers as an option, start looking for a later year or different, but still very similar, model that was offered with delay wipers. If the models are close enough, you may be able to cobble together a system of factory parts that will work. Or, you may find a related model of a more upscale / luxurious vehicle that has the same basic body style (say, a Pontiac that is similar to your Chevy) and the more upscale car did come with delay wipers as an option. The parts should be close enough to make it work -- but you will have to do some hunting. Your primary problem will be the switch itself. They will likely be different between the cars. Some creativity might be needed, but the basics aren't too hard.

    One example of this is that my 1973 Buick did not have delay wipers as an option. But starting in 1974, delay wipers were an available option. The two years are nearly identical so many parts swap without incident -- including most (if not all) of the dash pieces. I was able to confirm this by comparing the part numbers and application years for the non-delay wiper switch and motor. They were the same and the wiper switch and motor were labeled as "delay wiper only" pieces. Based on this search of the parts numbers, I can reasonably infer that the wiper linkage is the same. Only the motor, wiring and switch are different. The delay switch mounts in the same place as the non-delay switch. The wiper motor mounts identically and you need to connect a few new wires between the switch and the wiper motor. Based on the hunting through parts and service manuals and some research at my local parts store, it turns out that all I need is the delay style wiper switch, delay style wiper motor, and a separate wiring harness that goes between the two from a 1974 or 1975 full-size Buick. That means the delay functionality is built into the switch and the motor -- no separate controller box is used. The switch I found on eBay. The wiper motor is available as a rebuilt unit at my local parts store. The extra wiring harness can be found in a junkyard, or if need be, fabricated from scratch. Here is the wiring diagram from the 1974 Buick Shop Manual. The separate delay wiper harness indicated in red. Once I collect the three "delay wiper only" pieces (motor, switch, harness), the changeover is as simple as replacing the motor and switch with the delay pieces, and hooking up the new wiring harness between them. It looks like it goes through a separate hole and grommet in the firewall. So I'll need to grab that from the donor car and note the location where I need to drill the hole in my firewall.

    A similar situation is what happened on my 1975 Suburban. Delay wipers were not available in any of the Chevy or GMC trucks until 1978, and in that year they did a slight redesign of the dash and they changed the wiring around a bit. The newer style switch is very similar to the one I have. You slide it from left to right to go from off to low and then to high speed for the wipers. The big change for a delay unit is that you can twist the knob as well as slide it. The rotation controls the delay when in "delay" mode. The later switch is slightly larger where it mounts to the dash, but it does mount the same way. So there are no major problems here. The big problem here is the wiring. The colors of all the wires change a good bit with the introduction of the new dash design and the wiring at the wiper motor is a bit different as well. In particular, the later model wiper motors expose an extra connection for the switch that trips when the wipers are in the "park" position. In the earlier model wiper motors, this switch is internally connected to ground while in the later model wiring, this switch is connected to ground only when the wiper switch is in the delay and off positions. I can either modify my existing wiper motor to make this connection available externally so I can make the new switch work with my existing motor. Or I will need to bolt the new style motor onto my older truck and make it work with my existing linkage. In either case, I will need to run one new wire up under the dash to connect it to the wiper switch. Check these for details:

Build A System From Later Model Parts

    If nothing is directly compatible with your car, your next choice is to start hunting for similar factory systems in later cars. This is an extension of the previous options. Basically you are looking for something that is "as similar" as possible. Things to care about here are

    Keep in mind the switch is the hardest and most critical part to get right since it is an "appearance and functional" item that isn't easy to fabricate and can't be found in the parts store. The switch has to look right and function correctly for the conversion to be as seamless as possible.

    This route is more plausible than it might sound at first. Wiring for common things like wiper motors doesn't change too much over the years within a specific brand of cars. Ford, GM and Chrysler each do things a certain way and they don't change it much from year to year. This is because it costs money to change things. And if it works, they don't want to spend the money. You can take advantage of this. When a manufacturer added delay wipers as an option to any of their cars later on, they usually picked a way to do it that introduced as little change as possible into the existing system. The bulk of the wiring, and sometimes even the wiper motor, will be the same. Often only the switch and a few other things are added on and you can easily splice into the existing system once you figure out how the new system works. It all depends on the specifics of the system used on your car originally.

    If you are in a situation where you need to cobble together parts to make things work, it will likely require custom design and fabrication of the wiring harness to make it all work. The specific wire connectors and the way the wires are routed through the wiring harness will change from year to year, requiring you to splice together the right pieces of the wiring harnesses from both cars to make it work. You will need the wiring diagrams for both the original and donor vehicles and you will need to completely understand them. You may end up fabricating the wiper motor wiring harness entirely from scratch using a wiring diagram you create.

    As as example, my 1964 Ranchero uses a rotary style wiper switch. The Ranchero is a specific model in the Falcon lineup and most of that shares with the early Mustangs and Cougars. The same basic style of rotary wiper switch was used in a number of Ford vehicles in that era. Working through things, I found out that starting in 1969, most of the Ford line-up started offering delay wipers as an option and many of these vehicles used a rotary switch. This picture (left) shows the basics of how the switch works.

    Some poking around on the 'net revealed that by combining the delay style switch and delay control box from any '70's Ford F-Series pickup, along with the wiper motor and wiring harness from that same era truck, would net you a complete bolt-in delay wiper setup with almost no wiring changes needed. (I have a page dedicated to this specific swap if you want more details.) I had originally found out that the 1969 Cougar had the same style switch and delay wipers as an option, but the wiper motor was wired completely differently than mine. It was also under the hood instead of behind the dash like mine was. I knew I would have to replace my wiper motor as it was a single-speed design. So I started researching what motors might work and found out that the wiper motor from the F-Series pickups would fit. The parts cost me about $50 and once I had all the parts, the installation took an afternoon.


Aftermarket Solutions

    If you can find an aftermarket system designed for your car, then you may opt to use that. How you end up using the system depends on the exact details of the conversion kit you buy. How integrated you make things with the original controls depends largely on your skills and what is included in the system you buy. For example, there is a kit available from Detroit Speed for an early Camaros and Chevelles to convert them to delay wipers. I also found a kit from New Port Engineering to convert almost any early vacuum wiper setup to electric and they offer a delay option with their kits.

    In the case of my 1958 Buick, the first problem is that is uses vacuum power wipers. They are notoriously unreliable and fussy. So the first step up was to find a way to convert them to electric wipers. The bolt-in kit I found from New Port Engineering converts the wiper motor itself from vacuum to electric and has all the needed wiring. But the switch they supply is not a factory-style switch. The factory wiper switch on this car is a unique lever and cable arrangement that controls a variable sized orifice on the vacuum line going into the vacuum motor and it allows for infinitely variable wiper speeds. (Seriously, though - it's pretty cool !)

   The biggest functional factor here will be the replacement electric wiper motor that will then enable me to have reliable electric wipers and a basic package that I can then add delay wipers too as desired. After that, I have the functional issues with the switch (aka, how do I control it as a driver) and mounting / packaging issues -- keeping the car looking reasonably stock while making things work easily while using parts I can actually get my hands on. I could have custom switches built but that costs big money. They offer a delay option with the wipers but it's the same style switch. The good news is that they control the delay from the switch side. So adding delay wipers sometime after I get the electric wiper conversion done, won't be too hard. I have lots of options for the switch and how I use it -- ranging from just mounting the new switch under the dash (aka, just use what they gave me) on up to some really wild custom arrangements that I've brainstormed about on a dedicate page for doing the electric wiper + delay conversion on this car

    Basically, I saw an ad for "bolt-in vacuum to electric wiper conversions with a delay option" in a "hot rod" magazine. I called New Port Engineering to talk to them about it. I compared the details they sent me with the factory manuals and the factory wiper switch assembly to figure out the possible plans of action. The switch style is a rotary switch similar to the one used on the Ford delay systems. You rotate the switch from off into an area that controls the delay. You can also rotate it to the "low" and "high" positions. Some switch designs might put the delay portion between "off" and "low." Others do it in the other direction from "off" like Ford did. In any event, the new electrical switch is not directly compatible with my original wiper switch (see the dedicated page for details) but I could make it functional easily by adding the new switch under the dash. Making it integrate with the stock dash and switch will be a lot more work -- but can be done.

The Cheap and Ugly Route

   If you can't find an aftermarket system, you can get a simple $20 "generic delay wiper add-on" box from your local parts store and adapt it to your car. In this case, the wiring may be provided - it all depends on your car and what particular add-on delay controller box you get. You will either need to just tack the box to your dash (yuck) or take it apart and figure out how to mount the switches into your existing dash so they look good and work right. This is entirely up to your skills and it is the least defined of the options you have. It's also going to be the hardest to get to work "right" if you have a "depressed park" system like I have on my 1973 Buick (see the notes below on depressed park systems in the tidbits section). It can go from a simple add-on on up to almost being the same as a full-on custom system you build yourself. It all depends on your needs and how particular you are about integrating it with your existing controls.

Custom Solutions to Unique Problems

    The final option is a full-on custom system of some kind. The actual wiring of a delay system is not that hard but getting the right switches into the right places and getting all of the bits to work right together can be difficult at best. At this end of the range of possibilities, you are only limited by your imagination, electrical / mechanical knowledge, and the parts (switches, motors, etc.) that you can get your hands on. The actual delay circuit is pretty simple but tracking down the right switches and making it all work in the car will take time. If you chose this option, you should read through the "Arcane Technical Details" section below.

Any other tidbits?

    The hardest part of these types of conversions is simply getting all of the information about the wiring in both the original car and the "donor" car. You also need to know all the details about what is different in the delay wiper option wiring in the "donor" car as compared to a car without delay wipers so you know how comparable the base model wiring is to the wiring in your car. Often times it will be close enough to "just work." Other times, it will require some creative effort to make it work.

    The first few years that a new option is introduced on a car, the factory shop manual will usually go to great lengths to explain it so that the dealership mechanics will learn about it and know how to service it properly. They're no brighter than the average population and the option / feature is brand new in that "first year." So all they have to go on, are the descriptions in the manuals. Since the option is new to the driving public as well, general awareness of the option, how it works, and how to fix it is very low to non-existent. Thus, that first year factory shop manual is often like having your very own "Servicing <insert option / feature here> For Dummies" when you find the right section of the manual. Look for these "first year" manuals to help explain the factory systems when doing this sort of conversion on in understanding any "feature" in your car. The help these "first year" manuals provide is often invaluable.

   You should know what year and model your car is. So the first step is to go get a factory manual with the wiring diagrams for your car. Then you need to know what year that delay wipers were first offered in your car (the "donor" car). Then you need to get a factory manual with wiring diagrams for that year as well. Once you have figured out what is different in the wiring, then you can compare what will work and what will not. In some cases, stuff plugs right in. In others, things are totally different. You need to understand how the systems work and how they can be interfaced together to get the desired results. Especially in cases where the wiring colors change between the original and "donor" cars, you have to really stare at the diagrams pretty hard to understand everything. Compare wiring diagrams between your car and the "donor" car extensively -- you may be able to re-use more than you think. If you are swapping in the delay wiper parts from a similar vehicle, often some (if not all) of the factory wiring will remain on every model, just not in use, when the delay option is not in place on a given car. The same is true when looking for a "donor" vehicle. You may be able to cut out pieces of the wiring harness and use them, even from cars that did not have the delay options. Since the wiring is the hardest bit to find (motors are available rebuilt because they wear, and switches can be found in swap meets or on eBay), this could be particularly handy. The switch will be visually similar to the non-delay switch for the same year / make / model car and mounts in the same location. Most (if not all) of the wiring to the switch will usually be the same, sometimes a few extra wires get added. As you compare and try to understand things, it helps to focus first on what is the same. Then by process of elimination, you can find out what needs to be added or changed. For example, by this process I know that on the 1974 Buick delay wiper system, they only added a separate two-wire harness between the switch and the wiper motor. On a 1978 Chevy Truck delay wiper system, they added a different switch and a delay control box that plugs into the harness between the switch and the main wiring harness. The Ford systems of the 70's era are similar with a different switch and a delay controller box that plugs in between the wiper motor and the rest of the harness. Other than perhaps an extra ground connection, no extra connections are needed. In all cases a different switch is needed, and on the Buick, a different wiper motor is needed as well.

    The GM wiper systems (at least the older ones I'm used to working on) are really weird at first glance because the switch operates on the ground side of the system instead of the power side. Power first flows to the wiper motor, and the dash switch controls how that power gets grounded. This makes it easy for the park feature to work (since the motor has power all the time). But bad grounds or shorts in the wiring can create some really funky and hard to troubleshoot problems -- stuff like the wipers will be on anytime the car is on or that the wipers will turn on but will not turn off. This also "inverts" things a bit. Instead of "battery -> switch -> motor -> ground" the power flows from "battery -> motor -> switch -> ground" -- and some of the details can really trip you up and make your head hurt as you first try to understand things. Because power goes to the wiper motor first, turning the dash switch to "off" doesn't mean the wipers will stop. They still have power and will continue to run until they complete their "park" cycle. Little details like this matter a lot to delay wiper systems.

    The pre-delay GM wiper systems had different wiper motors than the later systems that came with delay wipers as an option. This is because the earlier systems incorporated the parking wiring right into the motor with no external wiring or switches needed, typically by grounding the motor through an "is the wiper parked yet" switch. To allow delay wipers to work with this system, GM typically had to expose one extra wire from the wiper motor -- the "park switch" wire needed to go to the dash switch and then to ground instead of being grounded internally.

    If you have a "depressed park" style wiper system (such as on my 1973 Buick), then you are in for the most trouble as the non-delay systems are very hard to get working correctly so that the blades do not "park" during the delay cycle. You will either have to use a different wiper motor that supports the functionality you need, or figure out how to modify your existing motor to have that functionality. The key is that the "auto-park" system will include a way for the blades to go all the way down into the depressed park position when you turn the wipers off. They typically use a cam of some sort that is engaged electrically to force this to happen when the dash switch is in the "off" position so that the final rotation of the wiper motor forces the blades to a lower position and then the motor is turned off automatically. When you turn the wipers back on, the cam action is reversed so that the blades rise up and then normal wiper action begins. What matters here is that for each delay activation, you want to have the wipers go through one full stroke and return to the bottom of their normal range of motion, but not into the depressed park position. Most wiper motors I've seen use a combination of mechanical and electrical pieces to make this happen, and modification of the mechanical parts is a non-trivial undertaking that I would strongly discourage. If you plan on changing the wiper motor out, the things you will care about are how it mounts to the firewall, how it mounts to the linkage, and how much travel it imparts to the linkage. The amount of travel is typically determined by the distance the "eccentric" is from the center of the rotating shaft.

    If you're too young to know what a vacuum wiper system is, count yourself as lucky. They use vacuum from the engine to power a motor that moves the blades. They are temperamental, underpowered, and the wipers slow down when you rev the engine too fast. Yuck! If you have one of these systems, convert it to an electrical system as soon as possible and get it over with. See notes above on my 1958 Buick conversion for ideas and details.

Arcane Technical Details

    This is a bit of arcane electrical trivia that tells you how the delay functionality actually works. They generally all follow the same principle, and use basically the same parts. The switch that controls the amount of delay is a variable resistor, or in the case of a "fixed delay" system (where you can select from a few different delay periods) it connects to resistors of different values. The more resistance you introduce into the circuit, the longer the delay between wiper sweeps. There is a relay that is used to "turn on" the system for an instant, and the "auto-park" circuit is typically used to power the system through the rest of the cycle. For "depressed park" systems, it's usually a related circuit to the auto-park that powers the system through the rest of the cycle. The resistor at the switch and the relay are connected by a timing circuit which is a fixed resistor connected to a capacitor, some diodes, and a few other devices such that it will spit out a "square wave" voltage output, with the duration of the low voltage portion changing based on the resistance at the switch. There are diodes in place to prevent any "feedback" into the rest of the system. When you activate the delay circuit, the output voltage goes to +12V for a few seconds, then drops back to zero for some length of time based on the variable resistance; goes to +12V again; and repeats until you turn it off. This is a "square wave voltage output" circuit and it's a classic "Electronics 101" project. So, if you know your electronics, you should recognize this circuit right away as a simple pulse generator. If not, take an "Electronics 101" course (or get a book on basic electronics) and you'll figure this out pretty quickly.

   The fine folks over at have an excellent description of the basic circuit for Delay Wipers in their Circuits section. I've mocked up a complete diagram for two basic circuits styles. The first is with external resistors to control wiper speed on a single speed motor. The second is with a wiper motor with built in high and low speed leads. If I ever find enough time, I might try to mock up a typical GM style wiper system (non-depressed park) with resistors to control speed and the switch on the ground side of the system.

    Note that one interesting wrinkle is when the delay period activates, I'm told the circuit above will not cycle the wipers the first time until after the delay period. You really want the system to activate the wipers first, then turn the power off for a while; then on again; then off. It's very important to the driver when the "on" and "off" parts of the pulse happen in relation to when they move the dash switch.

   Another potential wrinkle is how your wiper motor handles the auto-park feature. Some simply have an extra power feed to the motor that will auto-park the wipers if none of the other leads are on. Other styles require that the switching mechanism apply power to the "park" lead only when the low or high leads are not powered for it to work right. This is very important because the park circuit is what completes the single sweep of the wipers when you are in delay mode. (All the delay circuit does it get the wipers going -- you can think of it as simulating your turning the wiper switch "on" and immediately "off" again every few seconds.) If you have a motor with a park lead that cannot have power when either the low or high leads do, I have designed a simple circuit to get things working. Please be aware that I have not been able to test it yet on one of my vehicles, so I am just offering this information here as a way to get your idea hamster going to solve this problem.

    To make this work in a simple system, you really only need two diodes and a relay. A diode is just a one way valve and you can use them to hook both wiper leads (low and high) together as a "trigger wire" without causing "cross-talk" between them. Without the diodes, the system would act as if you had turned on "low" and "high" at the same time and probably do bad things like draw way too much current and maybe even burn out your wiper motor. With the diodes, none of the bad stuff happens and the trigger wire will simply be energized if the wipers are in 'delay," "low" or "high" mode. You can then hook that trigger wire up to the coil of a normally closed relay that opens the connection from the power source to the park lead on the wiper motor and get the desired result. When the trigger wire has power, the relay opens and the park circuit gets no power. When the trigger wire does not have power, the relay is closed at the park circuit gets power so it can park the wiper blades. That means that when you turn off the wipers or the delay feature is in the "off" period between sweeps, the relay is not powered and that allows the park circuit to get power. Other than the diodes, the key here is that you must use a relay with normally closed contacts - it's inverted from normal. I took the two circuits above and added in this new feature to create these diagrams

    If you do use my ideas for the park circuit, there is one other feature you might want to add in. I call it "key-off auto-park" and it allows the wiper blades to automatically park themselves if you turn off the ignition with the wiper switch on. (Normally, the wiper blades would stop wherever they were at when the ignition was turned off and remain there until the ignition was turned back on, at which point the wipers would continue.) To be able to wire up this feature, you need to use a circuit where you can easily hook up the park circuit to a different power source from the one that provides power to the rest of the wiper system. My suggested ones above have this ability. You also need to be sure that your wiper motor does not draw any power from the park lead when the motor is in the "off and parked" position. If it does, and you hook the park lead up to the battery, you will quickly drain your battery with the car off -- that's bad. So, what's the trick? Simple - hook up the power that feeds the NC relay to a power source (fused, of course) that is always live instead of one that is controlled by the ignition switch. The diagrams would look something like the ones below.

   It's a simple and subtle change, but I think it's a neat feature to have. It does have the drawback of not being able to stop the wipers mid-stroke if you wanted to for some reason such as changing the wiper blades, but you should change the blades with the system parked anyway.

    As you do this sort of work, keep in mind that the exact way the circuit is created and wired will change depending on the rest of the wiper system. The delay functionality is designed to blend into an existing bunch of wires as seamlessly as possible. This is especially important for the GM wiper systems since the switches operate on the ground side of the circuit and because of that, the circuit diagram could look a bit weird until you stare at it for a bit. Other than that, this is pretty straightforward electronics stuff. This fine feature that the auto manufacturers charge people a decent chunk of money ($20-$60?) to put on the car, originally really only cost them about $2 in parts and labor to add. Now that's what I call a nice profit margin...

Comments? Kudos? Got some parts you'd like to buy / sell / barter / swap? Nasty comments about my web page so far? You can email Mike.

v. December 2005

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