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Old 04-04-2020, 03:40 PM   #1
bdoggie72
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Smile Brake/Stop light switch or ground issue?

Hi All,

'New to the group and I have searched but still have some questions. I inherited my grandfather's '30 A Deluxe and have slowly been fixing a few minor issues. I'm also new to wrenching any car.

One I noticed the other day was that the brake/stop lights didn't work when I pressed on the pedal. The car has dual stop lights in the back and from what I've read it could be a bad stop light switch. The stop lights have two bulbs each, and one bulb (the brake light) will go on when I turn on the switch at the steering wheel. The headlights also work.

While I was looking at the battery, too, I noticed that there wasn't a ground strap connected to the battery. My Dad recently replaced the battery and it's possible that he forgot to attach it again, but is it also possible that the battery is grounded elsewhere? Could this be causing my brake light issue or should I try to just replace the switch first? Thank you very much.
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Old 04-04-2020, 03:47 PM   #2
Werner
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Default Re: Brake/Stop light switch or ground issue?

Willkommen.

If you bridge the two cable connections of the switch with a cable and the brake lights light up, then the switch is either defective or the actuation path is too short.
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Old 04-04-2020, 03:49 PM   #3
bdoggie72
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Default Re: Brake/Stop light switch or ground issue?

Thanks, Werner. Will give that a try.
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Old 04-04-2020, 03:54 PM   #4
30 Closed Cab PU
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Default Re: Brake/Stop light switch or ground issue?

Quote:
Originally Posted by bdoggie72 View Post
Hi All,





While I was looking at the battery, too, I noticed that there wasn't a ground strap connected to the battery. My Dad recently replaced the battery and it's possible that he forgot to attach it again, but is it also possible that the battery is grounded elsewhere? Could this be causing my brake light issue or should I try to just replace the switch first? Thank you very much.


You seem to be saying there is absolutely no cable wiring attached to one of the battery posts? A battery can not power anything if it is disconnected. If yes then nothing is working. Maybe I am reading this incorrectly.
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Old 04-04-2020, 05:32 PM   #5
bdoggie72
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Default Re: Brake/Stop light switch or ground issue?

Sorry if I'm not being clear. The battery is connected to both leads, but shouldn't there also be a third lead to ground that is bolted to the frame or something?

Anyway, I tried the bridge suggestion that Werner gave and the lights still don't work, so looking like it's not a switch issue, but a wire issue somewhere.
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Old 04-04-2020, 05:50 PM   #6
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Default Re: Brake/Stop light switch or ground issue?

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Wiring Diagram


https://lesmodela.files.wordpress.co...ng-diagram.pdf


You need the right tools to do diagnosis. A roadmap is essential with wiring.


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Old 04-04-2020, 06:08 PM   #7
bdoggie72
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Default Re: Brake/Stop light switch or ground issue?

Thank you, Joe. Following the wires, etc. everything looks ok. Old, but ok so far. Was going to check out the light switch block next, perhaps only out of curiosity as not sure if there's anything there that could be wrong.
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Old 04-04-2020, 06:41 PM   #8
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Default Re: Brake/Stop light switch or ground issue?

Yes, originally there is a woven flat non-insulated large cable going from the battery to the Frame.


Find which battery post goes to the starter. The other battery post should have the flat woven cable going to the frame.


Originally Model As had the Positive side of the battery going to the frame (positive ground).


However many have been changed to negative ground and have the flat woven cable going to the frame, on the battery negative (negative ground). Negative ground usually is done when converting to a 12v battery system.
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Old 04-04-2020, 06:43 PM   #9
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Default Re: Brake/Stop light switch or ground issue?

Quote:
Originally Posted by bdoggie72 View Post
Thank you, Joe. Following the wires, etc. everything looks ok. Old, but ok so far. Was going to check out the light switch block next, perhaps only out of curiosity as not sure if there's anything there that could be wrong.
Please add a general location to your profile. There may well be a Ford Barn member near you that can help.

I have helped many new Model A owners out with issues like this over the phone. Feel free to send me a private message or email through the Ford Barn and I will send you my phone number.

If the engine starts and runs, then the battery hook up is fine. We can walk through troubleshooting the rest over the phone.

If you did not inherit any Model A books with the car, I would suggest you get 2 to start: the Model A Mechanic's Handbook and the Diagnostics Troubleshooting Guide. One helps you find the problem, the other helps you fix it.

https://mafca.com/cart/index.php?productID=166

https://mafca.com/cart/index.php?productID=168

These are very simple cars, designed to be maintained by the average person in 1929. With some reference material and some guidance, you can do this.
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Old 04-04-2020, 06:52 PM   #10
nick c
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Default Re: Brake/Stop light switch or ground issue?

I had a brand new one but spent too much time trying to make it work, I gave up and threw it away, went to the auto parts store and used a modern brake lite switch, had to drill 1 hole in cross member. My truck is a 29 AA.
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Old 04-04-2020, 07:25 PM   #11
Patrick L.
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Default Re: Brake/Stop light switch or ground issue?

Several things
Look at the battery. Where do the 2 leads go ? One [ negative] goes to the starter. The other ]positive] goes to a ground usually the frame next to the battery which makes it hard to see. There has to be a battery ground for anything to work.

Get a voltmeter or plain ole test light. Check one side of the brake light switch, There should be power to that switch all the time. One lead should be hot. Once the pedal is depressed the other lead should also be hot. You can also jump across the two terminals and the lights should turn. If there is no power to the switch, provide power and see if that works. That power comes from the light switch, but, it can really come from anywhere. If you end up getting power thru the switch correctly and the lights don't work. Then remove the bulbs and check for power to the tail lights and the brake lights. If there is power and the lights don't come on them there is either a bad bulb[s] or a poor ground.
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Old 04-05-2020, 08:14 AM   #12
bdoggie72
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Default Re: Brake/Stop light switch or ground issue?

All the replies are really appreciated, and I have somethings to check out now based on the input.

For the battery, the negative lead goes to the starter. The positive lead appears to go a aftermarket kill switch located right at the bottom of the seat. I need to remove the seat and floor to get a better look at everything, but I'm guessing that is where the ground is, too, as headlights work, etc. Just not the brake lights.

Again, thanks for the guidance! Really helpful to a new guy here.

I have memories riding around in this car with my grandfather when I was a kid and it's been fun getting it back on the road and driving my kids around the block. I'm sure it's not just me, but these cars seem to always have a sentimental place in people's hearts.

Thanks again and stay safe out there.
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Old 04-05-2020, 09:29 AM   #13
rotorwrench
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Default Re: Brake/Stop light switch or ground issue?

These old designs didn't have provisions for circuit protective devices like a simple glass fuse. Some folks add one at the starter power connection where the small wire attaches then goes on to attach to the amp meter. A lot of folks disconnected the battery when not using the vehicle. The large cut off switches were used to make the disconnect a lot less troublesome. Less sparking occurs if the ground cable is disconnected.

The light switch should only affect the running lights of the vehicle. The brake light circuit is a separate circuit that draws power even if the light switch is off. My guess on the brake light that comes on with the switch is that the wiring is crossed on that lamp assembly or there is a cross short between wires in the harness. A lot of folks add the second tail light for safety purposes. It was still normal to have a single tail light in that era.

Brake light switches for the 30 & 31 cars fit to the center cross member and are a pull type switch. The 28 & 29 cars mounted it in a more weather protected area so there can be problems with these switches due to that. As was mentioned, the reproduction switches are problematic due to lack of quality in manufacture so this doesn't help. A&L is the only manufacturer that tries to manufacture a working switch for the 30/31 model As. They are available from most restoration parts sources for the model A and a priced around $50. If they go bad, A&L will stand behind their product by all accounts.
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