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Old 06-13-2015, 05:13 PM   #1
TonyM
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Default Dash lights when I press the brake pedal

I have a 1937 Ford stock with 6 Volt system.

1st Problem: A few weeks ago I noticed that when I press the brake pedal the dash lights come on. If I turn off the dash light switch, the dash lights do not come on when I press the brake pedal. When I press the brake pedal I get no brake lights no matter what position the switch is in. No brake lights with headlight switch activated. So I get dash lights when I push the brake pedal. All my lights worked correctly in the past. Where would this be crossed up at?


2nd Problem: Today I installed a new dash/cowl harness. All went well with the install. When I started the car after installing the new dash harness I noticed that the ammeter is working backwards--when I floor it the needle goes negative. When I turn on the headlights, the needle goes positive. Exactly the opposite way that it should work. Any ideas as to why this would happen with the new dash harness? Is the yellow wire looped through the ammeter the wrong way?


I still have the brake light/dash light problem after installing the new dash/cowl harness.

Please help. All replies greatly appreciated.

Thanks.
TM
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Old 06-13-2015, 05:16 PM   #2
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Default Re: Dash lights when I press the brake pedal

Yes.......looped the wrong way thru ammeter........easy fix! DD
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Old 06-13-2015, 05:18 PM   #3
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Default Re: Dash lights when I press the brake pedal

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Yes.......looped the wrong way thru ammeter........easy fix! DD
Okay. Looks like that one is solved. I suspected as much.

Big Time Thanks CoopMan!!!


Now the dash lights/brake light issue needs to be solved.
Stilll need help with that.
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Old 06-13-2015, 05:21 PM   #4
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Default Re: Dash lights when I press the brake pedal

Tony, I'm tempted to make a joke here, but... The brake light switch and the dash light sources are switched, so just trace those back to sources and change them back.

Yes, the yellow wire needs to be disconnected and run through the ammeter loop in the opposite direction.
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Old 06-13-2015, 05:34 PM   #5
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Default Re: Dash lights when I press the brake pedal

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Okay. Looks like that one is solved. I suspected as much.

Big Time Thanks CoopMan!!!


Now the dash lights/brake light issue needs to be solved.
Stilll need help with that.
OK, looking at Mac's handy drawing below, the only common point I see between the two switches (brake and inst. lites) is the MAIN lighting switch itself at the bottom end of the steering box. Maybe a short (think sneak circuit) there. Look at the drawing below. I'll scratch my butt some more over this. DD

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Old 06-13-2015, 06:54 PM   #6
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Default Re: Dash lights when I press the brake pedal

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Brake Light circuit should be HOT all the time. The Dash Lights are wired in with the Tail Lights. I would guess there may be a problem within the switch itself. Don't know if it is something you would want to do, but there is no need for the brake wire (Green) to even be connected to the Lighting Switch. Looks like they were just using it for a junction point. You could disconnect the Green wire from the Lighting Switch and connect it to any HOT source. It would at least shed some light on what is going on.
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Old 06-13-2015, 07:17 PM   #7
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Default Re: Dash lights when I press the brake pedal

Sounds like brake lights are looking for a ground through dash lights. Pete
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Old 06-13-2015, 07:38 PM   #8
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Default Re: Dash lights when I press the brake pedal

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Sounds like brake lights are looking for a ground through dash lights. Pete

I'll second that.

Any time I have a strange acting electrical problem I look for a ground problem.

I once had a suburban that when it was in reverse you could turn the key off and it would continue running. Turns out that the backup light was looking for ground and feeding the ignition. Strange but, true.
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Old 06-13-2015, 08:59 PM   #9
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Default Re: Dash lights when I press the brake pedal

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Brake Light circuit should be HOT all the time. The Dash Lights are wired in with the Tail Lights. I would guess there may be a problem within the switch itself. Don't know if it is something you would want to do, but there is no need for the brake wire (Green) to even be connected to the Lighting Switch. Looks like they were just using it for a junction point. You could disconnect the Green wire from the Lighting Switch and connect it to any HOT source. It would at least shed some light on what is going on.
I'm not so sure that would be a good idea. The need is to go through the lighting fuse. With the brake light switch itself being iffy, no fuse to protect the circuit would be a significant fire danger.
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Old 06-13-2015, 09:02 PM   #10
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Default Re: Dash lights when I press the brake pedal

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I'm not so sure that would be a good idea. The need is to go through the lighting fuse. With the brake light switch itself being iffy, no fuse to protect the circuit would be a significant fire danger.
Agree, I would just wire it straight from the fuse to the brake switch and skip the lighting switch. No need to skip the fuse.
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Old 06-13-2015, 10:41 PM   #11
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Default Re: Dash lights when I press the brake pedal

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I'm not so sure that would be a good idea. The need is to go through the lighting fuse. With the brake light switch itself being iffy, no fuse to protect the circuit would be a significant fire danger.
Thanks all who responded.

Alan and JSeery:

Okay, So I can bypass the headlight switch body by connecting the green brake light wire to the hot side of the fuse block? And this might solve the problem and offer fuse protection to the circuit? I hope I am getting it.

Should I try a new brake light switch anyways? The one I have is a modern repro.

Will investigate on Sunday.

Thanks guys.
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Old 06-14-2015, 03:11 AM   #12
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Default Re: Dash lights when I press the brake pedal

Tony, We might have a whole different animal here than we were thinking... Do you have mechanical brakes or hydraulic? The brake switch is different and it's late, my brain hurts already...
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Old 06-14-2015, 03:41 AM   #13
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Default Re: Dash lights when I press the brake pedal

Tony, You have a very simple problem of no ground on your rear tail lamp housings. This is a very common fault on even modern cars and trucks. As a quick test connect a jumper wire between the tail light metal body and a good ground like the bumper or chassis and recheck your stop and tail lights. I presume your 1937 ford has stock type rear lights. Do this test before you do any of the other alterations to wiring which have been suggested. Good luck, regards, Kevin.
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Old 06-14-2015, 01:10 PM   #14
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Default Re: Dash lights when I press the brake pedal

Okay, I re-looped the ammeter wire and that problem is solved. Works perfectly.

Brake Light/Dash Light Problem: I connected the green wire to the hot side of the fuse and the brake light / dash light problem is still there. When I press the brake pedal, the dash lights come on. Could it be the switch itself? It is a modern repro.

Alan, the brakes are stock Henry Ford Cables.

Thanks to all who responded.

Last edited by TonyM; 06-14-2015 at 01:17 PM.
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Old 06-14-2015, 01:15 PM   #15
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Default Re: Dash lights when I press the brake pedal

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Tony, You have a very simple problem of no ground on your rear tail lamp housings. This is a very common fault on even modern cars and trucks. As a quick test connect a jumper wire between the tail light metal body and a good ground like the bumper or chassis and recheck your stop and tail lights. I presume your 1937 ford has stock type rear lights. Do this test before you do any of the other alterations to wiring which have been suggested. Good luck, regards, Kevin.
Koates, I am going to go out and get a double alligator set up so I can ground the tail light housings. See if that works.

One question: If the taillight housings need to be grounded now, how come the brake lights operated for three years with out being grounded? This problem with the brake lights was first noticed in late December when I put the car away for the winter. Tail lights work, always have, it is the brake light action that is the problem.

If I ground the tail light housing to the frame and the problem persists, should I try a new brake light switch?

Thanks to all who helped. Still trying to solve.
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Old 06-14-2015, 01:25 PM   #16
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Default Re: Dash lights when I press the brake pedal

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Koates, I am going to go out and get a double alligator set up so I can ground the tail light housings. See if that works.

One question: If the taillight housings need to be grounded now, how come the brake lights operated for three years with out being grounded? This problem with the brake lights was first noticed in late December when I put the car away for the winter. Tail lights work, always have, it is the brake light action that is the problem.

If I ground the tail light housing to the frame and the problem persists, should I try a new brake light switch?

Thanks to all who helped. Still trying to solve.
Tony,
Take the tail light bulbs out and try it. It will tell you if it is the tail lights or not.

Bill
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Old 06-14-2015, 01:34 PM   #17
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Default Re: Dash lights when I press the brake pedal

IF the taillights work, the brake light ground MOST-LIKELY is not the problem, as the taillights share the same (GROUNDED) bulbs, which work.
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Old 06-14-2015, 01:49 PM   #18
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Default Re: Dash lights when I press the brake pedal

Is there a GREEN wire connected to BOTH sides of your BRAKE switch? If NOT green, what colors?

Since you can turn-off the INST LITE switch and the dash lites do not illuminate, there is nothing wrong with that switch. The brake lite switch also works properly, as moving it DOES turn something (dash lites) on. DD
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Old 06-14-2015, 01:50 PM   #19
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Default Re: Dash lights when I press the brake pedal

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IF the taillights work, the brake light ground MOST-LIKELY is not the problem, as the taillights share the same (GROUNDED) bulbs, which work.
The shared ground is path that the current follows through the dash lights to the dash light ground when the tail light ground is not sufficient to handle both. Removing the bulbs will interrupt this path.

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Old 06-15-2015, 06:51 AM   #20
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Default Re: Dash lights when I press the brake pedal

I would change the bulbs 1st. Used to run into that problem on 50's & 60's cars. Filament in the bulb shorts out and give you that result.
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