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lildrip049

1931 ford model a electrical problem

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A friend of mine has a 1931 model a. he recently replaced the generator with a 6 volt alternator. I was not part of this re-configuration. I am a muscle car guy having limited knowledge about 6 volt systems. I will tell you the new parts and the diagnostic checks i have perform.

new parts---battery, coil, distributor cap, points, rotor, plugs, plug copper connectors...i testet the distributor coil wire and it had continuity so it is not new.

problem ...car turns over but does not start.

tests: I have 6.4 volts on the positive and negative side of the coil with the key off--this is confusing to me because i would think that until i put the key on i would get a volt reading...maybe on the positive side of the coil with the key off, but not both positive and negative side of the coil.

When I turn the key on and try to start the car i get 6.4 volts on the negative side of the coil; but I only get 1.2 volts on the positive side of the coil. I tried to ground the coil wire and could not get a spark; i could not light an idiot light by touching the center of the coil and grounding the light.

I need help trying to trace this problem further...it seems to me that something is shorting out or the alternator install is wrong.

Also in setting the points I am putting the retard handle all the way up on the starting column that should be in the "retard" setting..am I correct in doing this to set the points. thx russ lildrip049@aol.com

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I am not up on the 6v alt conversions, but here is some info on the points/coil.

I don't know if that system still retains the positive ground, so I will use "hot" and "ground".

On a pos ground coil, the small terminal marked + goes to the condenser/points. The minus small terminal gets power from the key "on".

To see if the points are making/breaking; put a test light hooked to the small hot terminal on the coil that comes from the key, then ground the tip. Light should be on if key is on, as well as volts showing close to batt voltage at the batt.(if the points are open) Now switch the test light to the other small terminal that goes to the points/cond. That should have the light come on as the points are open; and the light should go off when the points are closed.

I'd have to look at a book on "A" timing, but there is a bolt up front on the timing cover that looks like a pointer. Take it out, turn the bolt around to stick in the hole while slowly rotating the crank. It will drop into a slight depression at TDC.

Then, I am not positive, but I think you then set the lever to full retard, and then loosen the screw under the rotor to adjust the dist cam lobe to be just starting to opening the points. That screw lets the dist cam lobe part, to spin on the dist shaft. Other cars, you'd rotate the dist.

Lets say the coil was internally shorted out, or the condenser was shorted to ground...the test light (placed on that terminal on the coil that goes to the cond/points) won't come on, regardless of if the points are open or closed. Same is true if the wire is shorted from the coil to the cond.

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After you get the points working so that the test light comes on/goes off as the points close and open, you should see a spark at the points each time the points start to open. And also when the points just start to open, that should make the coil wire spark if held slightly away from a ground source, like the cyl head.

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Best thing to do is forget the alternator and go back to a Model A generator. The alternator will not correct other electrical problems ! I would replace the wiring harness(an easy job on an "A") and return to the original setup. If your car is repaired CORRECTLY there is no need to alter the original configuration and it will save a lot of messing around! I ran an "A" for 16 yrs in the stock configuration and only had to replace 1 battery!

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Fords better idea the coil will have power on both sides as the key switch is between the coil and the distributor. the 6v alternator should be pos. ground and hooks up same as the generator.

The test about opening the points and closing the mentioned earlier is the best way to check if there is spark A's have a bad habit of getting a thin film of crud on the points a it becomes an insulator.

I have installed 6v alternators on early fords and others with no problems.

Al

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Turn on the "pop out " switch on the dash( ignition contact key). Is there power to the points in the on position?

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Thx for the info..it really helps...have a question...on the pos ground coil (marked +) going the condensor and the coil minus terminal connected to the key "on" switch should i be getting any voltage reading on the + or - sides of the coil with the key in the off position.....thx russ lildrip049@aol.com

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Alfre...thx for the info...still a little confused though...with the key in the off position should I be getting 6.4 volts on the negative or the positive side of the coil, or both...I would think that I would only get the 6.4 volts reading on the negative side..thx russ lildrip049@aol.com

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With the key off you should have about the same voltage on both lugs. the key is between the coil and distributer.

Al

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post-35932-143141748918_thumb.jpgHere's a wiring diagram for the Model A. Note that the two terminals on the junction box are always hot, key on or key off. Because of that, the short black wire from the terminal box going to the primary winding in the coil will give you a voltage reading at either terminal on the coil.

The orginal style ignition switch was unusual too. When the ignition was turned off, what it did was ground that red wire, essentially creating a closed circuit all time so that the points opening and closing had no effect. Replacement type ignition switches either open or close the wire in the armored cable going to the distributor.

Was the car running before he replaced the generator with the alternator?

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thx for the diagram and the info...the car was running before the replacement of the generator with a 6 volt alternator...the owner of the car did not the dim lights so he converted, replacing the generator....thx russ lildrip049@aol.com

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That is correct voltage with the key on and points closed now place a peace of paper between the points with the key on and the voltage should be the same on both coil lugs if not the armored cable has a short in it.

Al

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thx for the info.....will work on the car later this week or early next week....will advise you on my results...problem with snow down here...russ

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Lildrip, the advise above is right on. Don't forget when the coil is charged through the circuit, there will be current draw of about 1.5 amps in a 6 volt car. Advise get a copy of Les Andrews Model A repair shop manual. It is a great learning tool. Ron

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thx for the diagram and the info...the car was running before the replacement of the generator with a 6 volt alternator...the owner of the car did not the dim lights so he converted, replacing the generator....thx russ lildrip049@aol.com

Is the alternator a 6V positive ground single wire configuration?

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Sorry to be a little late to respond but it sounds lilke you may still need some advice. A Model A Ford electrical system is really simple. It is, however, important to follow a step by step process to determine what is wrong when trying to diagnose a Model A electrical problem. It would really be great for you to buy a copy of Les Andrew's Model A Ford Mechanics Handbook. It has diagnostic charts that would help you solve this problem quickly.

Since I don't feel like typing a lot, I am going to cut and past from a link on the Technical Questions and Answers on the MAFCA website at the following link:

MAFCA Tech Q&A - Engine Other

Following the MAFCA Answer below should help you diagnose the problem...

Answer:

Sounds like you have a problem in the ignition circuit. Here are the checks to make:

  • Yellow wire connected from post on starter switch to terminal box post (post on passenger side of terminal box).
  • Ammeter (-) side connects to passenger side post on terminal box.
  • Ammeter (+) side connects to driver side post on terminal box.
  • Black wire connects from driver side post on terminal box to coil (-) terminal.
  • Red wire connects from coil (+) terminal to ignition switch.
  • Yellow/Black wire also connects from driver side terminal box post to the cut out terminal. That completes the ignition wiring except for the ignition cable and distributor plate.
  • Here is a voltage check of the circuit:
  • Connect the (+) side of your volt meter to a good ground point on the engine or frame.
  • Touch the (-) probe to the passenger side terminal box wing nut. Read 6 volts.
  • Touch the probe to the driver side terminal box wing nut. Read 6 volts.
  • Touch the probe to the (-) terminal on coil. Read 6 volts.
  • Touch the probe to the (+) terminal on coil. Read 6 volts.
  • Place a piece of paper between the point contacts.
  • NOW TURN IGNITION KEY ON.
  • Touch the probe to the end of the points arm, read 6 volts.
  • Remove paper between points. Open and close points and look for spark each time points open, (no spark means bad condenser, replace condenser).
  • If points are sparking then disconnect the coil center (high tension wire) from the distributor cap (leave connected at distributor end). Place the free end of the coil wire about 1/8" from one of the engine head nuts. Crank the engine over with the ignition key on. There should be a bright blue arc from the coil wire to the nut (ground point). No arc means bad coil.

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Matt...thx so much for providing the diagnotis that i need to do to trace this problem...since the car hasc not started for over 1 year, it there anything that i can do to prime the carburetor which is enclosed----thx again ..russ lildrip049@aol.com

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As soon as you are sure the electrical system is doing what it is doing, then you need to make sure that the fuel system is also working correctly. Hopefully you have good fresh fuel in the tank. The fuel system is really simple. It basically includes the Gas Tank, Gas Shut off valve (I hope it is open), fuel line, carburetor. The fuel system is as simple as it can get, but it also needs to be trouble checked carefully if there is a problem.

After you know the electical system is operating correctly, you simply retard the spark (left lever up), gas (right) lever down a click or two, turn the key on, push the starter button, pull up the choke knob for a revolution or two and release and enjoy the sound of the engine running. (At least that is what should happen.)

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