Electrical gremlin-Help needed.

R

Russell in Tulsa

Senior Member
My brother sold his '29 last week and new owner said it quit running. He and I went there tonight to get her running and had a little bit of trouble.
We checked the terminal box and got the horn and lights to work. (The owner said they were working while Bro. talked him thru some early troubleshooting, but they weren't when we arrived.) Took the instrument cover loose and found 6.45V at the switch and 0 on the dist. side of the switch.
Turned switch on and have .55V on hot side and dizzy side, not the original 6.45V. Whats going on?
I'll try to find the color wire diagram on this site, it may help.
Hope one of you can shed some light on this.
We tried a known good coil and upper dizzy plate before we saw the voltage discrepancy at the switch.
The ammeter checks good and had over 6V there and the map light.
Where and why are we loosing proper voltage at the switch.
Thanks. Russell.
 
My early 28 Roadster did the same exact thing. It had the pop out ignition switch, I took it apart, cleaned it up, spray some electrical contact spray on it, took emory cloth to the contacts, put it back together and resolved my problem.

Had the same problem again, on the same car. I replaced the instrument panel cover with a shiney new one. The pop-out ignition switch fit in it very snug and would get stuck.

Tried to modify the cheap-o cover, continued to get stuck. Put the old one back on and threw new junk panel in the garbage.

The ammeter didn't fit in correctly too, rotated it.

I'm still a novice after owning two Model As in six years, but I'm thinking ignition switch.
 
We also used a jumper from starter to the coil to bypass the switch and still no spark at the dizzy. We need to replace the points as the rubbing block was about gone and not opening the points good enough. This may have been the problem at first, but the low voltage at the repro switch was puzzleing.

We will try a known good switch and check volts again. Thanks.

Any more thoughts?
 
Sounds like you have a bad connection or short to ground in the ignition circuit. The lower plate could be shorting against the distributor casting, the lower or upper plates could be at fault. It is possible the ignition switch can be at fault as well. Get a good digital voltmeter and start troubleshooting. I would go to the distributor first as It is easy to get to.... has the highest probability. Make sure you don't screw the distributor connector from the ignition cable in too far as some repro lower plates can be pushed in to the casting and short. Many folks screw them in too far.

Just to be sure, disconnect the headlight harness at the cutout/generator or alternator, whichever you are running, and of course leave the engine harness connected.

Good luck!
Larry S
St. Charles, MO
 
If you have a stock ignition system the coil has 6V all the time and the ignition switch controls the
ground path through the points. You need to get a wiring diagram.

Bob
 
Bob C said:
If you have a stock ignition system the coil has 6V all the time and the ignition switch controls the
ground path through the points. You need to get a wiring diagram.

Bob
Click to expand...

Bob C is correct. The ignition switch is between the coil and the points. Your jumper did nothing to bypass the ignition switch. Model"A"s are wired a little different than newer cars where the ignition switch is between the battery and the coil, I have never had good luck with reproduced pop out ignition switches. Maybe they are better now, but 12 years ago they were junk.
 
So far it sounds good. The points must have been closed when you turned the switch on and checked the voltage. The .55 volts is the line loss and resistence loss of the switch contacts and points contacts.

Do the same check again, except this time step on the starter and you should see the voltage go up and down as the points close and open.
 
Brother got it running and the next day the new owner said it quit again.
He said he thinks it is the wire under the plate and will check it first. Thanks for your reply's.
 
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