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Old 04-02-2017, 07:03 PM   #1
forestb
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Tail light ground problem?

So I just built a new bracket for mounting my tail lights on my step side. My problem is that now the tail lights don't work. The blinkers and the break lights work fine. They all worked before I mounted using the new bracket. I know that the original brackets served as the ground. In order for the new bracket to ground the electricity now has to travel to a stainless steel bolt that is connected to a aluminum bracket and then through another stainless bolt. Do the problems I am having sound like a ground problem?
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Old 04-02-2017, 07:21 PM   #2
Keith Seymore
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Re: Tail light ground problem?

Yes.

I had an '80 stepside (similar setup). I would remove the tail light brackets every year to repaint them, and replaced the star washer bolts with stainless bolts.

Over time all of the rear lights got funky. It took a while to figure it out but I assumed it was the ground. I ran a separate wire from the bulb socket, through the harness conduit to a clean location on the frame (on both the LH and RH lamp).

Worked like a champ after that.

K
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Old 04-03-2017, 10:30 AM   #3
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Re: Tail light ground problem?

Thanks that is what I was thinking.
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Old 04-03-2017, 11:04 AM   #4
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Re: Tail light ground problem?

The taillights and the brake/directional lights all share the same path to ground so it seems odd that one would work and not the other with a bad ground. Also, what's the chances of both sides only partially not working. Just sayn'.
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Old 04-03-2017, 11:15 AM   #5
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Re: Tail light ground problem?

Could it be that I have the two wires switched?
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Old 04-03-2017, 01:06 PM   #6
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Re: Tail light ground problem?

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Originally Posted by TopFuel1966 View Post
The taillights and the brake/directional lights all share the same path to ground so it seems odd that one would work and not the other with a bad ground. Also, what's the chances of both sides only partially not working. Just sayn'.
Whenever I would ask the electrical system engineer a question he would say "it's a bad ground" before I even could finish asking...



My recommendation would be to ensure a good ground first, and then start chasing any other schematic problems. No ground = unexplainable funkiness.

K
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Old 04-10-2017, 04:35 PM   #7
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Re: Tail light ground problem?

what the heck happened there
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Old 04-12-2017, 10:50 AM   #8
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Re: Tail light ground problem?

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Originally Posted by Keith Seymore View Post
Whenever I would ask the electrical system engineer a question he would say "it's a bad ground" before I even could finish asking...



My recommendation would be to ensure a good ground first, and then start chasing any other schematic problems. No ground = unexplainable funkiness.

K
That still doesn't explain why a double filament bulb with a common ground connection between the two burns one filament but not the other.
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Old 04-13-2017, 12:13 AM   #9
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Re: Tail light ground problem?

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That still doesn't explain why a double filament bulb with a common ground connection between the two burns one filament but not the other.
Basically it can't unless the circuit is designed to trip on more than bulb current.
Nothing in the above posts suggest one filament (they share a ground) doing anything other than the other. An 1175 is a 2 filament bulb that share a ground/return.

Last edited by franken; 04-13-2017 at 12:19 AM.
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Old 04-13-2017, 12:35 AM   #10
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Re: Tail light ground problem?

From memory, i think tailight circuit is the brown wire. Get under there with a test light and see if there's power on the brown wire with the lights on. Make sure the light is grounded (make it light up with a known good circuit) If yes, then it's a ground, bad bulb or a junk tailight assembly.
Ancient, crappy trailer wires can really mess things up. Get rid of it if not needed.
IMHO, as a professional auto electrician, these old trucks have some amazingly durable wiring and components.
I hate to think what modern car circuits will look like in 50 years.
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Old 04-13-2017, 12:58 PM   #11
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Re: Tail light ground problem?

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That still doesn't explain why a double filament bulb with a common ground connection between the two burns one filament but not the other.
When there is a bad ground, (or non-existent), the turn signals and brake lights, (same filament) will appear to work. What is happening is the power from the brake switch or turn signals is going through the filament but is seeking a ground through the tail light filament. Both filaments will be in series with each other which results in only the tail light filament illuminating. (It takes less power for it to light.) But it will be slightly dimmer.
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Old 05-06-2017, 06:37 PM   #12
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Re: Tail light ground problem?

I think I found my problem. When I turn on my lights and use a test light the only one that didn't light up was the tail light white. I tuck the switch appart I found this. I think the little coil of wire is supposed to connect to the brass circle that the little nub of a wire is sticking out of. Both ends have a little ball on the end.
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Old 05-06-2017, 06:40 PM   #13
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Re: Tail light ground problem?

No, that's just the rheostat to dim the instrument cluster lights. Have you tried disconnecting the firewall connector that houses the two blue wires?
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Old 05-06-2017, 06:42 PM   #14
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Re: Tail light ground problem?

I tried grounding the lights to the frame and it still didn't work so I went to the switch.
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Old 05-06-2017, 06:43 PM   #15
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Re: Tail light ground problem?

BTW, ignore my question. I have two threads going in my head at the moment!
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Old 05-06-2017, 06:44 PM   #16
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Re: Tail light ground problem?

It doesn't have one anymore. It is a new painless harness
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Old 05-06-2017, 06:46 PM   #17
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Re: Tail light ground problem?

Should there be power coming out of my switch into the tail light wire?
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Old 05-06-2017, 06:47 PM   #18
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Re: Tail light ground problem?

Quote:
Originally Posted by forestb View Post
I think I found my problem. When I turn on my lights and use a test light the only one that didn't light up was the tail light white. I tuck the switch appart I found this. I think the little coil of wire is supposed to connect to the brass circle that the little nub of a wire is sticking out of. Both ends have a little ball on the end.
Yeah, there may have been a short, although the fuse should have protected the rheostat. It just burned in half.
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Old 05-06-2017, 06:52 PM   #19
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Re: Tail light ground problem?

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Should there be power coming out of my switch into the tail light wire?
Yes, the brown wire. Use your test light to see if there is voltage at that wire at the switch. If there is, that will show the problem is somewhere between the switch and the tail lights.
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Old 05-07-2017, 06:39 PM   #20
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Re: Tail light ground problem?

Ok so there is no voltage at that wire coming out of the switch so I think it is the switch.
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Old 05-07-2017, 09:17 PM   #21
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Re: Tail light ground problem?

Did you ever check the fuse? Have to ask. That's the first thing that should be checked.
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Old 05-07-2017, 09:39 PM   #22
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Re: Tail light ground problem?

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Originally Posted by damnyankee36 View Post
Did you ever check the fuse? Have to ask. That's the first thing that should be checked.
There is power going into the headlight switch and the headlights are working. Is there a ground in between the switch and the tail lights?
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Old 05-07-2017, 09:44 PM   #23
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Re: Tail light ground problem?

I tried to check the fusses but it is a painless block and I didn't see one specifically for tail lights
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Old 05-07-2017, 10:23 PM   #24
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Re: Tail light ground problem?

Definitely find it. That could be the problem.
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Old 05-13-2017, 08:38 PM   #25
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Re: Tail light ground problem?

Checked all my fuses and they are all fine. I think it is the headlight switch sense I am getting power from all the wires going into it except for the tail light wire.
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