Electrical Problem

[Robert/Texas]

I’m having an electrical problem with my ’28 roadster. The car has an almost new 6-volt battery which cranks the engine over well, but the engine won’t start. The voltmeter stays at zero while cranking with the ignition switch on or when turning on the lights or blowing the horn. As I get 6.3 volts on both sides of the terminal box, I don’t think that there is anything wrong with the ammeter.

The car has a new diode style cutout. The BAT side of the cutout shows 6.3 volts and the ARM sideshows zero volts with the ignition both off or on. With the engine not running, I think that this is what it should be.

With the ignition off and a piece of thin cardboard slipped between the points, I only get voltage (6.2 volts) on the movable side with the ignition on.

Both the plus and minus sides of the coil show 6.3 volts with the ignition off or on.

The problem started some weeks ago. My wife and took the car for a long ride. The next day the battery was dead, and I replaced it with a new one. I also replaced mechanical cutout with another old mechanical one. We went for another ride and all was fine.

Sometime later, when we went for another drive, we didn’t get far, and the engine shut down. It started back up while I was coasting down a hill, so I turned around and headed home. Again, it stalled close to our house and we pushed it into my workshop.

I installed a new diode style cutout, thinking that this second old mechanical cutout had failed but that didn’t help, and here’s where I’m at now.

I’m having trouble thinking this through, (probably due to my age).

All help and suggestions will be greatly appreciated.

Thanks, Robert

[Ruth]

I think the earlier cars were wired on the 'wrong' side of the ammeter so the ignition draw doesn't show like the later cars.

I don't see anywhere that you checked for spark out of the coil and to your plugs?

Originally Posted by Robert/Texas

With the ignition off and a piece of thin cardboard slipped between the points, the moveable side shows 2.45 volts and the non-movable side shows 6.3 volts with the ignition on. With the ignition off, both sides show 6.3 volts.

This does not make since to me. With the ignition off, you sgould have no voltage at the points.

[Patrick L.]

If I'm reading the problem correctly, it sounds as if there is a problem somewhere from the ignition switch to the points.

Key on there should be battery voltage [6v] at the open point arm and no voltage to the ground side of the points. When points are closed there should be no voltage.

Key off there should be no voltage to points.

It seems like the switch may be grounding against the tank. The insolation in the primary cable could be bad.

[Robert/Texas]

Thanks Ruth and Patrick.
I just re-checked the points and they are behaving as they should. I don't know why I got those bad readings but I've corrected my original post. The points are much too close, so I'll correct that. I'm surprised the car ran as good as it did until all this happened.
Robert

[Wick]

Do you have a pop out switch or just a cable with a wire running through it? The cable with the wire inside will short out inside with age. Shake the cable and see if it starts,also make sure the Spark rod is not hitting the cable.

[Mulletwagon]

Sponsored Links (Register now to hide all advertisements)

Voltage to both coil terminals - switch on or off - is normal. Wiring to the ignition switch and to the distro merit further investigation.

[Robert/Texas]

Thanks Wick and Mulletwagen.
I re-set the points to .018 and it still won't start. It has an after-market ignition switch disguised with an armored cover. I'm ready to drink a beer and hope to get back to it tomorrow morning.
Robert

[barnstuf]

To help you with your testing remember that current only goes one way thru a diode cutout. The Model A is positive ground. The Model T is negative ground. It follows that a Model A cutout and a Model T diode cutout look alike but they do NOT replace each other.

[Patrick L.]

Remove sparklers, place a plug wire/strip about 1/4" from the good ground source, turn key on, hit starter and see if there is a spark to the ground.

[rotorwrench]

The old spark check as previously mentioned is a good first start in troubleshooting. I always do the easiest thing first. The condenser is the next thing to easily replace with a no blow & check. If still no spark, a volt/ohm meter set on Ohms resistance can be used to check the ignition circuit for opens or high resistance in the switch to breaker circuit or switch to coil side. The power side of the coil can be checked for voltage easy enough since it's hot all the time. Coils can go bad too but I check everything else before changing it out. The coil should have about 1.5 ohms from small terminal to small terminal.

The model A is somewhat unique in the fact that the ignition switch is connected in the breaker side of the circuit. More modern cars switch the hot side of the coil on the power in feed and the breaker side is just connected from the distributor to one of the coil primary terminals. Which side of the two small coil terminals is connected to what is where the polarity comes in. Positive ground systems use the positive terminal for the breaker as a general rule but it's usually best to have a polarity tester to make certain the coil will function properly.

[30 Closed Cab PU]

Originally Posted by Ruth

I think the earlier cars were wired on the 'wrong' side of the ammeter so the ignition draw doesn't show like the later cars.

I don't see anywhere that you checked for spark out of the coil and to your plugs?



This does not make since to me. With the ignition off, you sgould have no voltage at the points.

https://www.fordbarn.com/forum/showt...ammeter+wiring



In this string the wiring change on the ammeter wiring is discussed. If wired this way the ammeter has a slight wiggle from the points opening/closing. Very useful if your car does not start/fire, the wiggle indicates that the points/ignition switch/coil/wiring are somewhat functioning correctly.
Does not give status of the high voltage. That can be checked by taking a lead off the spark plug, placing it 1/4 inch to 1/8 inch away from the spark plug, and using the starter rod with the ignition switch on . You should see a nice blue spark.

[Robert/Texas]

Thanks to all of you for your help.

barnstuff
I'm sure that the diode is positive ground. I bought it from Snyder's and the box it came in and the sticker on the bottom of it say so.

Patrick L.
I just tried this and didn't get a spark.

rotorwrench
I don't have a new condenser but I'll get one when I order some parts. It's always good to have a spare one. The volt/ohm meter shows 1.6 ohms and 6.3volts.
Closed Cab PU
The ammeter used to wiggle when I cranked the engine as it still does on my other A, a March '28 open cab pickup with most of the early features.

Thanks again to all of you, Robert

[wmws]

So far no one has mentioned the wire going between the upper and lower plate in the distributor. I know you said you are getting voltage to the movable point arm with the ignition on but it may be intermittent. Try moving the retard leaver while you are checking for voltage at the point arm. Maybe using a test light might make it easier to see.

[Patrick L.]

OK, the problem seems to be primary side of the ignition.

Check to make sure the switch and ignition cable are working as they should all the time [wiggle while cranking]. Then as mentioned check the upper/lower plate wire. Then comes the condenser and finally the coil as mentioned.

[Jacksonlll]

Try a new coil wire before you start taking things apart. This fooled a couple of our members last summer and they towed it in because of an old coil wire.

[ryanheacox]

I agree with Jack. If you have 6V at the points you should at least get a pop or a sputter. Have you also tried cleaning the points? It's unlikely that's the problem since you were driving recently but stranger things have happened and it's a quick test.

[Aarongriffey]

The model A is the ONLY car I know of that has the ignition switch wired between the coil
And points.
A simple...sure check
Remove the two parts of the distributor cap.
Turn the engine so the points are closed
Turn on the key.
Open the points with a wooden or plastic pointed object. Did the coil spark when you did that?

[Robert/Texas]

Thanks to all of you. I think that I’ve found the problem which now makes me feel kind of foolish. I’m farsighted and use reading glasses when looking at things up-close. I had misplaced the glasses and was using an old pair while testing the distributor and re-gapping the points.

This morning, after reading your posts, I started rechecking things. I found that the movable-side point was completely worn out. I’m surprise that it ran so well up to the point of failure.

I remembered that I had rebuilt this distributor some time in the past. Looking through my receipts, I found that I bought the parts from Bratton’s on 2/26/2001. The condenser on the receipt was noted as Short-Proof.

Although I should have figured this out sooner, I’ve gained a lot of knowledge from your posts. I’m going to order point-set and a spare condenser.

I’ll let you know if this solves the problem.

Many thanks again to all of you, Robert

[Jacksonlll]

Always have a spare coil wire.

[Robert/Texas]

Thanks Jackson, I'll put that on my list too.
Robert

[Robert/Texas]

The points and condenser came, and I installed them. The small plastic bag that the points came in was marked USA, but the points are garbage in my mind. Only a little more than half of the electrodes surfaces match and I feel that they will be short lived. I’m thinking that I ought to get a modern conversion kit to replace them if no good original style points are available. Suggestions welcome.

After this I checked to see if I would get some sparks at the points with the ignition on, using a hard, wooden pointed stick. No go, so I got my other Model A out and did the same thing and got lots of sparks.

As there is voltage (6.1 volts) at the point arm with the ignition switch on, I don’t think that it is either the switch or the wiring. Comments here are welcome too.

I get 1.6 ohm reading between the coil terminals, but I don’t know if this should be any assurance that the coil is good. Again, any help/suggestions are welcome.

Thanks much in advance, Robert

[katy]

As there is voltage (6.1 volts) at the point arm with the ignition switch on, I don’t think that it is either the switch or the wiring. Comments here are welcome too.

Your 6.1 volts is good if the points are open, switch on or off. Points closed, with the switch on, the voltage should drop to zero.

[30 Closed Cab PU]

Remove the condenser and try the sparks at the points test again - you would not be the 1st person to get a bad new condenser. Without the condenser you will get a very bright spark at the points.


Am not sure which points/plate set up you have, but points do not line up correctly on most reproduction points, and I believe correct points can not be sourced. However Brattons makes a points block that is tooled so they will align. Read the notes provided in the link.


https://www.brattons.com/machined-di...int-block.html


The primary resistance looks good. From the coil output to each wiring post should be about 7K ohms to 12 K ohms. If it is open or very high - suspect coil. Once in a while the measurement will check out OK, but the coil fails in the car under load.


With ignition on, points closed, does the points arm measure 0 Volts? If no, then you are not getting a ground on the Points Block.

[Jacksonlll]

If your point arm is hot with the key on, and no spark when closed, it is not making ground when closed. Try sparking between the hot arm and ground. You have to get a spark there. I can't believe that the point base is not grounded.

[The Master Cylinder]

Originally Posted by Robert/Texas

The points and condenser came, and I installed them. The small plastic bag that the points came in was marked USA, but the points are garbage in my mind. Only a little more than half of the electrodes surfaces match and I feel that they will be short lived.

Have you tried 'aligning' the the points and the point block? Bratton's has a really nice machined points block, IMO is better than the origial. Also clean the nice points. I have gotten some that did not make contact because of a film covering them.

[Robert/Texas]

Sponsored Links (Register now to hide all advertisements)

Thanks, katy, 30 Closed Cab PU, and JacksonIII

I checked all of your suggestions and believe that I have replaced a bad condenser with another bad one.

Resistance from the coil output from both the + and – posts registers 7.02 ohms
.
With the ignition points open and the ignition switch on, I get 5.89 volts at the point arm, but the other three scenarios yield zero volts. With the condenser removed, I get no sparks.

I really like the idea of the Bratton’s point block. I hope to order this and another condenser from them next week.

I bought both of my Model A’s back in 1989. I bought the “AR” OCPU first and some months later I bought this roadster as a “project car”. Now at age 85, this seems to be coming a project again. I have both cars parked next each other now so I can compare measurements.

Any further help will be appreciated.
Thanks again to all of you and I’ll keep you posted, hopefully next week.

Robert

[Jacksonlll]

Keep your old condensers. You will get a much smaller spark at the points when the condenser is in the circuit.

[30 Closed Cab PU]

Originally Posted by Robert/Texas

Thanks, katy, 30 Closed Cab PU, and JacksonIII

I checked all of your suggestions and believe that I have replaced a bad condenser with another bad one.

Resistance from the coil output from both the + and – posts registers 7.02 ohms
.
With the ignition points open and the ignition switch on, I get 5.89 volts at the point arm, but the other three scenarios yield zero volts. With the condenser removed, I get no sparks.

I really like the idea of the Bratton’s point block. I hope to order this and another condenser from them next week.

I bought both of my Model A’s back in 1989. I bought the “AR” OCPU first and some months later I bought this roadster as a “project car”. Now at age 85, this seems to be coming a project again. I have both cars parked next each other now so I can compare measurements.

Any further help will be appreciated.
Thanks again to all of you and I’ll keep you posted, hopefully next week.

Robert

Did you perhaps mean 7.02 K ohms instead of 7.02 ohms? If yes that would be a good reading. If actually 7.02 ohms coil secondary is bad/internally shorted. Either way maybe swap coils since you have a known good coil in the other A? You would not even have to mount it on the firewall to test.


Voltage readings on the points arm open and then closed seems OK.




Otherwise I am out of ideas

[katy]

Originally Posted by The Master Cylinder

Have you tried 'aligning' the the points and the point block? Bratton's has a really nice machined points block, IMO is better than the origial. Also clean the nice points. I have gotten some that did not make contact because of a film covering them.

I also had a mis-alignment problem w/new points so I just carefully filed the holes in the top plate to make the mounting block adjustable.

[Licensed to kill]

So, I pulled my A out for the first time in 2 years or so and could NOT get it to start. No spark. I looked a few things over and then did a search and came across this thread. I changed the coil wire as per Jacksonhill with a new 14G wire, saw nothing wrong with the old one but changed it anyway and it find right up. Not going to say I understand it but there you have it. Made up another wire and put it under the seat. Now that it's running, I will start a new thread on how to get to run properly. Thanks.

[old31]

Originally Posted by Jacksonlll

Try a new coil wire before you start taking things apart. This fooled a couple of our members last summer and they towed it in because of an old coil wire.

Curious, what would be a test that you could do to see if a high tension lead is good or bad?

[30 Closed Cab PU]

My father used to test old tractors coil wires and spark plug wires by grabbing onto the wire while it was running and feel how much it would shock him. When asked how he could tell good vs. bad he replied "experience". Did the same thing with electric fences. Old farmers, what can I say.

[History]

I've seen old mechanics do this, some of it was to show how tough I'm sure. I've only done this by accident.

I was talked into peeing on an electric fence when I was young and never got shocked. I believe it was because the shoes I wore, custom because of a partial amputation had rubber soles. I did this several times until my mom found out and told me what could happen. I guess I never did it barefoot.

I plan on getting an extra coil wire as Mr JacksonIII mentioned.

Originally Posted by 30 Closed Cab PU

My father used to test old tractors coil wires and spark plug wires by grabbing onto the wire while it was running and feel how much it would shock him. When asked how he could tell good vs. bad he replied "experience". Did the same thing with electric fences. Old farmers, what can I say.

[wmws]

Robert/Texas if you have voltage to the movable point arm but no spark past the points the juice is not getting to ground. I have heard of distributors so corroded or so much paint that they don't make a good ground path to the block. You could take a wire and ground the upper plate to the block or directly to the battery. Then take a wooden stick and open and close the points and see if you have a good spark coming out of the coil.

[Robert/Texas]

I got some parts from Bratton’s yesterday afternoon. I installed the “Machined Distributor Point Block” and the condenser last night. The points line up well now but still nothing is working.

I rechecked some of the voltages. From the junction box (both sides) to the point block, I got 6.1 volts. From the coil (plus or minus terminals), I got 5.8 volts. I got 5 .8 volts at the point arm with the ignition on.

Cranking the engine with the ignition on, I get no wiggle from the ammeter.

With the ignition on, I get no sparking when moving the point arm with a wooden stick. (I get lots of sparks when doing this to my other Model A.)

The battery is fully charged and measures 6.3 volts. It cranks the car well enough to move it around.

I just noticed that there is no power to the lights or horn. Now I’m thinking that there is something wrong with this side of the electrical system that’s causing my problem, but I can’t see how that could be.

Any further help/suggestions will be much appreciated.

Robert

[katy]

With the ignition on, I get no sparking when moving the point arm with a wooden stick. (I get lots of sparks when doing this to my other Model A.)

Try cleaning the points.

I just noticed that there is no power to the lights or horn. Now I’m thinking that there is something wrong with this side of the electrical system that’s causing my problem, but I can’t see how that could be.

Does the car have a fuse? If so, check and/or replace it.

[ryanheacox]

Just to make sure. When you found you had no lights or horn did you check to make sure you had power at both sides of the terminal box and coil? Sounding like you could have an intermittent bad connection somewhere. That is a problem on some harnesses where the terminals are crimped but not soldered.

[Robert/Texas]

My mistake.

The points are new and gapped @ .020.

I am getting power to the horn/light switch but the horn and lights don’t work. I opened the switch housing and removed the wire clips. I got 6.1 volts on the BAT clip. I believe that this plastic switch/disc has moved on the switch body as it cannot be properly assembled (spider prongs @ 6/12 o’clock position and the switch lever @ 6 o’clock). I believe that I installed this wiring with the then-available parts available in 1990.

I also hooked up a known good coil but that didn’t help although there was some corrosion on the positive terminal of the old one. Also, some of the wiring in the junction box looks a little frayed so I plan to investigate this tomorrow.

Yes, I do have 6.1 volts at both terminal box sides and both sides of the coil. I get 5.8 volts at the point arm, about the same voltage that I get in my other Model A but I don’t get sparks out of it like I do with the other car. This makes no sense to me.

Sorry for the confusion and thanks for your help.

Robert

[Jacksonlll]

Scratch a jumper between the open point arm and ground. It should spark.

[Badpuppy]

Look for a bad crimped wire connection somewhere. Wire and terminals can develop high resistance between them over time. Check between wire ends with an ohmmeter.

You can read the same voltage across megohms of resistance until you try to run current through it.

[1931 flamingo]

Have you checked the wire UNDER the top plate??
Paul in CT

[katy]

The points are new and gapped @ .020.

Are they clean and making good electrical contact? New points are notorious for having a film of oil on them and therefore not making good contact.

[Robert/Texas]

Eureka, I’ve found the problem. I removed the coil and terminal box. The wires in the box are in terrible shape (bare spots) and difficult to get out of the box as some are too short. It was obvious that there could be a short in there. I separated these wires and re-installed the coil. For the first time I got sparks between the points. I plan to figure out which wires need replacing before I do much else although first, I plan to time the distributor and try to start the engine.

Many thanks to all of you for your help and patience.

Robert

[1931 flamingo]

I'd get the whole dash harness. JMO
Paul in CT


GLAD you found the culpret.
Paul in CT

[Badpuppy]

Success is happiness.

[Robert/Texas]

Sponsored Links (Register now to hide all advertisements)

Thanks again to all of you.

I replaced all of the wiring which ended in the terminal box and/or dash. I even cut and spliced a new piece of wire on the ignition wire (the one that goes from the ignition switch to the distributor). I feel that this part of my problem but I’m having a distributor problem and plan to start a new thread about this.

Robert