Died while driving, now no start

G

gtoger

Junior Member
31 Model A, 6V system with alternator. We took the car for a ride a couple days ago and everything was running great. Suddenly and without warning, the car began backfiring horribly and lost power. I quickly determined there was no electric power. Got the car pulled over, found that the main fuse on top of the starter was blown. Replaced the fuse, but the car would not start. The starter cranks. I have headlights, taillights, dome light, instrument light. No horn. The aftermarket turnsignal/hazards do not work. And apparently, no ignition. The ammeter does not "dance" when cranking. Just stays flat in the middle. Thinking there's no spark, I checked for volts at the coil, and see 6V. Pulled the connector off a spark plug, set it near the post and saw no spark when cranking. Thinking it may be the coil, I replaced it with a 1.5ohm unit from the local parts store. Still no spark. There has to be something related to why the horn, ignition and the aftermarket turn signal unit all won't work. What is the commonality that I am failing to see? Ideas and advice welcomed!
 
Have you replaced the Terminal Box with an aftermarket one?

If so, check to see that both screws are tight up against the nuts, in other words, loosen the nuts all up to the rear one, and be sure the screw is still tight. Friend of mine had very similar problem and we found the screw had loosened up and backed out enough to tap the firewall and short out smoking the fuse.

Just a thought from experience.

My 2¢ worth
 
Why waste such valuable time guessing and experimenting with the hundreds of "different" Model A electrical failures reported that are experienced and told every year?

Get an analog multi-meter with a needle and a Model A wiring diagram.

Start at the power source, (battery), and follow the yellow, red, and black brick roads until the analog needle on the multi-meter does not move. That simple.

Not much different from using a road map from point A to point B ...... once you overcome the most horrific fear of reading a multi-meter and reading a piece of paper similar to a map ..... treat yourself to a Thomas Edison Baseball Cap ..... you deserve it !!!!
 
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If your horn does not work, you have blown a fuse (somewhere) or you burned a wire. Just chase it. Your wiring sounds strange. The horn and lights should be together and down stream from the fuse. Disconnect the light wiring from the alternator and put in a good fuse.
 
Do you have an additional FUSE in the system, possibly between the alternator and the horn? If so, check it for continuity.
 
Use the wiring diagram to trace out your issue.
 

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Do NOT start replacing parts until you have identified the problem. That is the biggest mistake most people make. Someone says "I had the same problem back in 1974 and I replaced the modular discombobulator and its been working good every since". Don't listen to the shotgun Joe's, get a multimeter and use the supplied wiring diagram and figure it out. Not only will you get it fixed right, but you'll be more educated for next time.
 
A. Never a bad idea to have several spare copies of a simple wiring diagram.

B. Next, mark the wiring diagram with a transparent felt tip marker ...... for example, if the battery (+) & (-) posts and cables are OK, mark these cables with your marker.

C. Continue marking each wire route, and every connection, marking everything that is in good order.

D. After traveling on your wire diagram map, you can see where you have been, and where you need to go, with no time consuming backtracking.

E. However, if you are under 30, usually a transparent marker and extra wiring diagrams are never needed.
 
You say you have 6 volts at the coil. I assume you mean the black wire feeding power to the coil. Now move your voltmeter to the red wire on the coil terminal, and see if it moves the meter needle as you crank the engine. It should be pulsing back and forth as the points open and close, and if it doesn't then the problem should be between that point and the points grounding.

Stop the engine with the points open and key on, then see if you have 6 volts at the movable points arm. If you do, then short the points contacts with a screwdriver and see if the coil wire sparks to a head nut. If you now get sparks, then the points contacts need to be cleaned, if they are opening and closing with a .020" gap.
 
The voltage comes from the same place for lights and horn (if wired stock) and we don't know how the directionals are wired so put those on the back burner for now and concentrate on the spark. Follow Toms instructions for troubleshooting that.

Let us know what you find,

Additional info here;

Won't start



Oh, welcome to the Barn.
 
Synchro909 said:
From the OP: There has to be something related to why the horn, ignition and the aftermarket turn signal unit all won't work.
How does a condenser affect these things? IMHO, I think we need to look elsewhere.
Click to expand...

Plugs foul.... I'd check them 1st..
Here is a great animated video on why it could be the condenser.... A faulty coil might be the issue or connection near that area.
https://youtu.be/W94iksaQwUo
 
Hi guys, thanks for all the input.

I've had limited time over the past few days to tinker, but my notes so far:


  • Although my profession has me working with electricity (-48VDC to 400VDC, 110VAC to 480VAC) every day, I haven't owned an analog multimeter for many years. Will try to dig one up that isn't complete junk.
  • I've verified the nuts on the junction box terminals are tight. The jbox terminals both show a good 6V.
  • The car has only 2 fuses that I have found. One on the starter, which I understand to be the master fuse, and one inline on the turn signal apparatus. Both fuses are good (tested for continuity as well as passing volts.)
  • I appreciate the diagram and will print out a few copies and trace as suggested.

I'm trying to embrace this 6VDC, positive ground system but admit to getting turned around in my head. It's just so different from every other car I've known, so that could be part of the intimidation factor. This is far from my first old car. Just the oldest. By far...
 
One can usually diagnose the system with a $1.49 12v test light..

Dont worry about the pos ground difference ,, think of it as normal
 
Harbor Freight has a quality (I know H/F and quality don't usually go together in the same sentence) test light for less than $5.

For a good analog meter, I like the Sperry SP-152A. They show up on ebay every few weeks.
 
At first instant, I thought much like response #15 ..... followed by medics using their jumper cables ....... and with no start ...... heart would not re-boot ....

Been over 15 days, hope driver is OK .......
 
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