Total Electrical Failure

Chris Van

Chris Van

Member
Hi Boffins

Please help:

I have been using my A as a daily driver for nearly ten years and yesterday for the first time ever she cut out on me. Stone dead as I was driving.

To get her started I hot wired her (put a wire between the starter motor and the coil) and then she started and drove perfectly and everything worked (lights, hooter, brake light) obviously being powered by the generator because the ammeter was still not moving at all.

When I got home and disconnected the hot wire everything is stone dead again. I took the dashboard off but could see nothing wrong and also squirted WD40 into the ignition switch but still nothing.

Have absolutely no idea what to do next. Any suggestions would be greatly appreciated.
 
You could jump around disconnecting, re-connecting, trying many things at one time & get it running ............... but never know why is stopped running.

However, if you start at the battery (+) & (-) and first check for a good solid ground for your battery, then proceed in a linear manner along the wires with a multi-meter, you have a better chance of determining exactly where your problem is located.

My first guess is your junction box may have a bad connection, maybe even corrosion on the connection, or a loose connection; but because electricity flows in wires like water in a pipe the multi-meter can locate where the flow stops.

Hope this helps.
 
Hi H.L. Thanks for the prompt reply. I'll get my friend with his multimeter to pop round and we can thence go through everything systematically - you are right, otherwise I will be undoing and doing up things till the cows come home.

700 rpm: Thanks for your prompt reply. To my knowledge my A does not have any fuses (it is a '31 Town Sedan)... it is totally original and still has the 6V system which has never given any problems until this day.
 
Hi Chris,

How nice ..... I have a late 1930 Town Sedan, August 1930 ..... good to have a roomy Model A when one wants to bring friends or family along for a ride.

Even though we cannot see electricity flowing through insulation, the multi-meter can verify the flow from connection to connection.
 
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You used a jumper wire between the starter and coil, so you have an open between the starter and coil feed wire. If someone added a fuse, check that first. Jump a wire between the two terminal box wing nuts. If it now works, then you have a bad ammeter or poor connection at the studs under the cover.

A test light is an inexpensive good testing tool for problems like this.

If you have an original popout, it may not be a good idea to spray WD-40 in it. People have reported that it's bad for potmetal.
 
wiring-diagramcolor2sm.jpg
 
I had a short in the terminal box of my 29 tudor which was caused by the metal tube from the generator sliding in and touching the voltage post of course blowing the fuse at the same time, it seemed when the steering wheel was turned right the chassis would shift enough to slide the tube into the wiring post. I solved that one by a coat of silicone adhesive around the box opening.
 
If HL, Tom and Mike can't help you will just have to buy a new car ( lol ). They are three of the best in the business !
Good luck, Wayne
 
Chris I give you credit for knowing how to hot wire the car, with the info at hand it should be pretty simple for you.
I keep a wire with alligator clips in both my cars btw. Never leave home without it.
 
Chris Van said:
Hi Boffins

Please help:

I have been using my A as a daily driver for nearly ten years and yesterday for the first time ever she cut out on me. Stone dead as I was driving.

To get her started I hot wired her (put a wire between the starter motor and the coil) and then she started and drove perfectly and everything worked (lights, hooter, brake light) obviously being powered by the generator because the ammeter was still not moving at all.

When I got home and disconnected the hot wire everything is stone dead again. I took the dashboard off but could see nothing wrong and also squirted WD40 into the ignition switch but still nothing.

Have absolutely no idea what to do next. Any suggestions would be greatly appreciated.
Click to expand...

If you look ant Mikes wiring diagram you can see that with your jumper you were bypassing the ammeter and feeding the coil, horn, and lights direct from the battery.

Bob
 
FWIW: In my opinion, anything is possible.

Even the electrical connection you "cleaned" at the coil could have been the culprit, especially in areas of high humidity which can cause increased oxidation.

Of more importance is that an instantaneous dead engine in heavy traffic is risky & scary in some cases, & even more scary is an electrical hit & miss fix without knowing the exact cause ........... like having the constant concern, "Can it happen again?"

Just hope you find it so to have peace of mind that it was found & corrected.
 
For those of us that are non-purists but just love the daily driver, is there a wiring diagram that shows the 12V negative ground conversion with a one wire alternator and a safety fuse on the starter? I have several versions of the 6V positive ground diagram and have penciled notes about changing the coil terminals and ammeter connections. I've been chasing a dead short even after a complete wiring harness replacement. Thanks!!
 
I will strongly second HL's recommendation for the multimeter. My Model A just flat stopped while out on the highway. First time I have ever had and it was a bit scary. I have moved recently and have yet to unearth my multimeter so was "guessing" at symptoms. Couldn't possibly be the popout switch that Dick Crabtree rebuilt, because well it's restored. (Not knocking Dick here, he is the best but stuff does wear and break in use....) It was an electrical problem-the popout switch which I replaced with a (shudder) NuRex repro that didn't fit all too well without some modification. Moral to the story-get that tester out and begin at the beginning!
 
paulizor said:
For those of us that are non-purists but just love the daily driver, is there a wiring diagram that shows the 12V negative ground conversion with a one wire alternator and a safety fuse on the starter? I have several versions of the 6V positive ground diagram and have penciled notes about changing the coil terminals and ammeter connections. I've been chasing a dead short even after a complete wiring harness replacement. Thanks!!
Click to expand...

Remove the single power wire to the alternator and see if you still have the dead short.

Do you have a 12 volt negative alternator to match the battery and ground?
 
It's a relatively new 12V negative ground alternator and all was a go for the first test after the harness replacement. Got two blocks down the road and the fuse blew. Big short blackened inside the fuse. Multimeter out and cannot find a short. Fuse replaced, runs and shows charging, all lights work and down the road I go. This time 3 blocks. Multimeter shows no short again. Power wire off the alternator would still leave the 2 yellow wires to the harness. Correct? I suspect driving vibration is grounding the lamps or horn circuits necessitating a manual trace for intermittent exposed wiring grounding somewhere.
 
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