Electrical Tips
by Randy Rundle
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            Does trouble shooting electrical problems make you feel like some Druid wizard auguring portents from chicken guts? NO MORE!! The Stovebolt Page Electrocutioner explains -- ELECTRICAL STUFF

      Randy Rundle, proprietor of 5th Avenue Antique Auto Parts, answers a few of the most common questions Stovebolters ask about working on their truck electrical systems. Randy is an absolute guru of antique automotive electrical systems and we are glad he's pitching in with us here at The Stovebolt Page. While we breathlessly await further installations, check out the Electrical Bay in the forms and talk to Randy, Andy Horvath and the others who get a charge out of talking electricity!

 

Battery Cables?

I have converted my 1950 Chevrolet 1/2-Ton to 12 volts -- What size battery cables should I be using?

In this case bigger is better and size does matter. The larger in diameter your cables are the greater volume of current they can carry with less electrical resistance (friction). The stock 12-volt cables were 8 ga from the factory.... the 6-volt were 4 ga. At least use the original 6-volt cables, and even better -- replace them with 1 ga like those used on diesel pickups. Your starter requires about 150-200 amps and most batteries provide 600 CCA (Cold Cranking Amps) these days. The weak link is usually the battery cables and related connections which fail to deliver enough of those 600 amps to the starter.

Watt Amps?

What exactly are "Watts" and how do they compare to "Amps" and "Volts?"....and why are some things advertised as having a watt rating (like headlamp bulbs) while others things like heater blower motors are said to "draw about 10 amps...?" Why is this so confusing...?

Volts -- using water and a garden hose as an example ... (Ok, a Walmart 5/8 diameter 50 footer with brass ends and quick attachment ends) the pressure behind the water in a garden hose is measured in pounds per square inch. This same measurement in electrical terms is called "volts." Volts or voltage is equal to the pressure behind the amps and is what forces the current thru the wires -- much like water pressure forces the water thru a garden hose.

Amps -- again, using water as an example ... the quantity of water passing thru a pipe at a given point is measured in gallons. In electrical terms the electricity passing thru a wire at a given point (like the amp gauge in the dash) is measured in "amps." The amps or amperage is what does the actual work and is equal to the volume of water in the garden hose.

Watts -- is the measurement that describes the total amount of energy being used or consumed. To figure watts simply multiply the amps times the voltage. So, a 6-volt heater blower motor that draws 10 amps of current on high will have a rating of 60 watts. And in reverse, if a heater blower motor has a rating of 60 watts, and the voltage of your truck's electrical system is 6-volts, then divide the 60 watts by 6 volts and you end up with 10 amps. That is the amount of current your blower motor will require from your charging system. If your system is 12 volts, simply divide the 60 watts by 12 (the voltage of your electrical system) and you will then know the heater blower motor will require 5 amps from your charging system. This works for all voltages. A watt is a watt is a watt no matter if it is the one under the hood of your truck or the one inside of your house.... it is the SAME thing!! An amp is also an amp no matter if your electrical system is 6-volt, 12-volt, or 110. And so it goes for voltage -- volts are volts no matter where you find them. And you thought electricians were so smart !!!!

Easy Switcheroo?

I've found a supplier of 6-volt internal regulators that fit GM Delcotron 12-volt (63-amp) alternator. Can you just switch out regulators and make a 6-volt alternator?

Ah, if it were only that easy! The 6-volt regulators (and the copy cats) have been around for about 10 years or so (in part because of me bribing the engineers to "prove they could build one correctly (using my specifications)" which they finally did. I am their largest customer. However, there is more to it than that. If you just install the 6-volt regulator into a standard 12-volt alternator, the results will be 6.5 volts and 30 amps. This is because when you reduce the voltage output (using the standard 12-volt alternator rotor and stator), the amperage output is also reduced by half as well. It takes an average of 36 amps to run everything in your truck before you add things like electric fuel pumps and fog lamps, etc. So, it is easy to see that the 30 amp output of your new alternator isn't going to be much better than the generator you are replacing. So I have my own stators wound using heavier copper wire and also use specially designed rotors (which cost just over twice what a standard rotor and stator costs to build) to get the 65 amps out of my 6-volt alternators. My regulators are also designed to charge 7.5 volts so the nominal voltage inside the battery is at or above 6-volts all of the time. I spent a year and a half figuring all of this out and ruined a pile of parts before I got it right. I too thought this would be easy to do in the beginning. So now you know the story.

Generator or Regulator - Who's to blame?

How do I know if a problem is related to the generator or the regulator?

This is a common question, so much so that I offer a postcard with the troubleshooting procedures on it as well as the proper way to polarize a generator to the regulator, which nobody knows how to do properly anymore. So before I begin this explanation anybody who wants a postcard suitable for attaching to the wall of the garage or toolbox just needs to send a dollar along with a self addressed #10 envelope to; Generator Postcard, 415 Court Street, Clay Center KS 67432.

The first thing that we all need to understand is that the amp gauge does not tell you if the charging system is working, per se. What it actually tells you is which direction the current is flowing to the battery -- to it (+) which is recharging or (-) which is taking current from the battery. The kind of discharge you describe is usually the result of a dead short, from a pinched wire, a bare wire rubbing on the frame, or in some cases by the points sticking in the regulator, which by the way most often happens as the result of some well-meaning mechanic trying to adjust the regulator up for more output. Usually the points get misaligned then welded together. This often shows up as a discharge on the amp gauge and really bright dash/headlights. The most common solution is to stop, get out, reach under the seat, grab a pair of pliers, raise the hood and beat on the cover of the regulator. Sometimes that would unstick the points. Even if it did not, it made you feel better by taking out your aggressions on the regulator cover.

Now for the fix. Use a jumper wire to ground the field terminal of the regulator to the engine block. Attach one end of the wire to the field terminal of the regulator. Attach the other end to a good ground on the engine block (like a bolt head or engine stud.) This will by-pass the regulator to see if the generator is working. If you increase the engine rpms and the output increases as shown on the amp gauge in the dash, the odds are good the generator is working, and the regulator is at fault. If there is no increase in output, remove the jumper wire from the engine block and strike it against the engine block. If you do not get any spark, this will confirm the generator is not working.

      Check out Randy's Fifth Avenue Internet Garage. He's got his regular Alternator Gazette (newsletter), Tech Tips (Battery, Ignition Coil Polarity, Headlight Relays, Gas Gauge Problems, Radiator Cooling Problems, Upgrading a Borg-Warner Overdrive to 12-volts, Which Radiator Works Best). And Randy has several publications listed in our Lots O' Links Publications page.

      And be sure to check out our extensive Forums discussions -- from General Truck talk, Electrical Bay, Big Bolts, Panels and Burbs, Engine and Driveline, Paint and Body, Interiors, Tool Chest -- The Stovebolt Collective can help in your quest and walk you through the mire and magic of working with old iron. ~~ Editor .         

v. 2000 / Update February 2006


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