Headlight Relay Question
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From: ROSEBRUGH ALBERTA
I used a multi meter and found absolutely no ground connection from the rear wiring harness to the frame battery etc.
There are 3 ground wires in that rear wiring harness and from back to front they enter the cabin just over the drivers rear wheel well and on the forward side of the drivers side wheel well, that wiring harness continues along the running board to the dash. But the 3 ground wires are not included. They have to be routed under the carpet to another grounding location and not connected. The carpet is all glued down and I prefer to not mess with it.
I have a strong feeling these ground wires were never connected since the car was factory altered in 1982. I believe everything was working through the ground on the fuel tank sending unit. It was wrong but it worked.
I coated the fuel tank with a heavy polyurethane coating and now is insulated and so lost that ground in the process. This exposed the grounding issue.
I have connected (soldered) the 3 original ground wires in that rear wiring harness to a 12 gauge wire and connect it to the frame and changes everything.
The lights work but something is still weird and exposes a problem related to the passenger side taillight and signal/brake light. Through trial and error I found the taillight wire and the ground wires were reversed. So the 12 volts was running backwards through the 1157 bulb and through both filaments. There is no short because everything is fiberglass and the same as Corvette. All I did was switch the ground wire with the taillight wire wires and it works properly.
So I'm about to make another ground connection to the frame (powder coated) and I should be good.
Am I ok to continue? Thx again, John
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From: Charlotte NC
You a re aware that your fuel tank is not the actual ground...but rather the ground wire that is in the connector you unplug to stop your electric fuel pump has the ground in it?? So the coating you applied is not hurting anything.
Here is where I am confused....slightly.
You wrote: Through trial and error I found the taillight wire and the ground wires were reversed. So the 12 volts was running backwards through the 1157 bulb and through both filaments. There is no short because everything is fiberglass and the same as Corvette. All I did was switch the ground wire with the taillight wire wires and it works properly.
SO if I read that correctly....the BLACK wire that is pushed into the side of your stop/turn/park light sockets was actually a 12 volt power source???
That is a new one for me. The reason being is that the rear wiring harness is connected up by your left hinge post area by the fuse panel and it should still be correctly color coded so the wires are all correct. but you never know when someone gets into the wirging and does stupid stuff due to not knowing what they are doing
You wrote: So I'm about to make another ground connection to the frame (powder coated) and I should be good.
Am I ok to continue?
I can only assume that you are OK to continue. You have done tests in ALL of the ways it can be tested...such as with NO headlights/running/park lights on and checking your brake, turn signal and hazards...and then turn on your headlights and see if they still work.
THAT is when you will have a problem is when the rear running/park lights are on and your try to use turn signals or brakes IF you do not have a good ground at each taillight socket in the correct terminal.
FOR WHAT THIS IS WORTH:
When checking wiring on light bulb circuits..it is wise to remove all of the bulbs associated with that specific circuit....because if you don't...it can cause you to scratch your head because the socket on the bulb is grounded when installed and it is also connected to the filaments which are 12 power when used. SO when the ignition is off...the wires that make the filaments glow are actually a ground IF the bulb is in the socket. Light bulbs are basically nothing more than a controlled short circuit...where pwoer and ground meet and glow...much like a MIG welder does.
DUB
Here is where I am confused....slightly.
You wrote: Through trial and error I found the taillight wire and the ground wires were reversed. So the 12 volts was running backwards through the 1157 bulb and through both filaments. There is no short because everything is fiberglass and the same as Corvette. All I did was switch the ground wire with the taillight wire wires and it works properly.
SO if I read that correctly....the BLACK wire that is pushed into the side of your stop/turn/park light sockets was actually a 12 volt power source???
That is a new one for me. The reason being is that the rear wiring harness is connected up by your left hinge post area by the fuse panel and it should still be correctly color coded so the wires are all correct. but you never know when someone gets into the wirging and does stupid stuff due to not knowing what they are doing
You wrote: So I'm about to make another ground connection to the frame (powder coated) and I should be good.
Am I ok to continue?
I can only assume that you are OK to continue. You have done tests in ALL of the ways it can be tested...such as with NO headlights/running/park lights on and checking your brake, turn signal and hazards...and then turn on your headlights and see if they still work.
THAT is when you will have a problem is when the rear running/park lights are on and your try to use turn signals or brakes IF you do not have a good ground at each taillight socket in the correct terminal.
FOR WHAT THIS IS WORTH:
When checking wiring on light bulb circuits..it is wise to remove all of the bulbs associated with that specific circuit....because if you don't...it can cause you to scratch your head because the socket on the bulb is grounded when installed and it is also connected to the filaments which are 12 power when used. SO when the ignition is off...the wires that make the filaments glow are actually a ground IF the bulb is in the socket. Light bulbs are basically nothing more than a controlled short circuit...where pwoer and ground meet and glow...much like a MIG welder does.
DUB
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Joined: Aug 2017
Posts: 140
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I thought it was strange to have three grounds all bolted to different locations within a couple feet of each other, but then i relised that they are not all for lights. One is for rear defrost....another for i dont know what....and the other probably is for somethong else that i dont know what....but they are deffinately there. I wonder how many people were left scratching their head with bad grounds but still getting lights on sometimes...lol...once you learn it its somethimg you NEVER forget....lol
Last edited by san; Sep 23, 2017 at 09:28 PM.
Thread Starter
Instructor
Joined: Mar 2013
Posts: 136
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From: ROSEBRUGH ALBERTA
You a re aware that your fuel tank is not the actual ground...but rather the ground wire that is in the connector you unplug to stop your electric fuel pump has the ground in it?? So the coating you applied is not hurting anything. I do understand this.
Here is where I am confused....slightly.
You wrote: Through trial and error I found the taillight wire and the ground wires were reversed. So the 12 volts was running backwards through the 1157 bulb and through both filaments. There is no short because everything is fiberglass and the same as Corvette. All I did was switch the ground wire with the taillight wire wires and it works properly.
SO if I read that correctly....the BLACK wire that is pushed into the side of your stop/turn/park light sockets was actually a 12 volt power source??? Yes, the black was plugged into the side but is a ground. The brown is 12 volts and plugged in the bottom. So that supplied 12 volts to the brass side of the 1157 and grounded the running/park side. I just had to reverse their location, install a temporary ground for testing and everything works properly. Was tough because I had to deal with 2 issues, not just one. Both 1157 filaments being lite up at the same time was my first clue.
That is a new one for me. The reason being is that the rear wiring harness is connected up by your left hinge post area by the fuse panel and it should still be correctly color coded so the wires are all correct. but you never know when someone gets into the wirging and does stupid stuff due to not knowing what they are doing. True. That's why I re did all the wiring with soldered and shrink wrap connections, split wire looms, nice wire supports and really nice routing. I can't stand poor workmanship and I don't care how long it takes me to figure it out and do it right.
You wrote: So I'm about to make another ground connection to the frame (powder coated) and I should be good.
Am I ok to continue?
I can only assume that you are OK to continue. You have done tests in ALL of the ways it can be tested...such as with NO headlights/running/park lights on and checking your brake, turn signal and hazards...and then turn on your headlights and see if they still work. Yes.
THAT is when you will have a problem is when the rear running/park lights are on and your try to use turn signals or brakes IF you do not have a good ground at each taillight socket in the correct terminal. Yes
FOR WHAT THIS IS WORTH:
When checking wiring on light bulb circuits..it is wise to remove all of the bulbs associated with that specific circuit....because if you don't...it can cause you to scratch your head because the socket on the bulb is grounded when installed and it is also connected to the filaments which are 12 power when used. SO when the ignition is off...the wires that make the filaments glow are actually a ground IF the bulb is in the socket. Light bulbs are basically nothing more than a controlled short circuit...where pwoer and ground meet and glow...much like a MIG welder does. Yes,..exactly and very well explained Mr Dubb. I thank you for your help and advise, much appreciated.
DUB
Here is where I am confused....slightly.
You wrote: Through trial and error I found the taillight wire and the ground wires were reversed. So the 12 volts was running backwards through the 1157 bulb and through both filaments. There is no short because everything is fiberglass and the same as Corvette. All I did was switch the ground wire with the taillight wire wires and it works properly.
SO if I read that correctly....the BLACK wire that is pushed into the side of your stop/turn/park light sockets was actually a 12 volt power source??? Yes, the black was plugged into the side but is a ground. The brown is 12 volts and plugged in the bottom. So that supplied 12 volts to the brass side of the 1157 and grounded the running/park side. I just had to reverse their location, install a temporary ground for testing and everything works properly. Was tough because I had to deal with 2 issues, not just one. Both 1157 filaments being lite up at the same time was my first clue.
That is a new one for me. The reason being is that the rear wiring harness is connected up by your left hinge post area by the fuse panel and it should still be correctly color coded so the wires are all correct. but you never know when someone gets into the wirging and does stupid stuff due to not knowing what they are doing. True. That's why I re did all the wiring with soldered and shrink wrap connections, split wire looms, nice wire supports and really nice routing. I can't stand poor workmanship and I don't care how long it takes me to figure it out and do it right.
You wrote: So I'm about to make another ground connection to the frame (powder coated) and I should be good.
Am I ok to continue?
I can only assume that you are OK to continue. You have done tests in ALL of the ways it can be tested...such as with NO headlights/running/park lights on and checking your brake, turn signal and hazards...and then turn on your headlights and see if they still work. Yes.
THAT is when you will have a problem is when the rear running/park lights are on and your try to use turn signals or brakes IF you do not have a good ground at each taillight socket in the correct terminal. Yes
FOR WHAT THIS IS WORTH:
When checking wiring on light bulb circuits..it is wise to remove all of the bulbs associated with that specific circuit....because if you don't...it can cause you to scratch your head because the socket on the bulb is grounded when installed and it is also connected to the filaments which are 12 power when used. SO when the ignition is off...the wires that make the filaments glow are actually a ground IF the bulb is in the socket. Light bulbs are basically nothing more than a controlled short circuit...where pwoer and ground meet and glow...much like a MIG welder does. Yes,..exactly and very well explained Mr Dubb. I thank you for your help and advise, much appreciated.
DUB
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Instructor
Joined: Mar 2013
Posts: 136
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From: ROSEBRUGH ALBERTA
Dub almost hit the nail on the head. You should have some ground connections under the trim behind seat...on the roof as well, you have.to remove those pieces of trim on the B-pillars....one on the roof, one on passengers side B-pillar, and i think there is one on drivers side as well...not sure....Yes, big purple wire from drivers B pillar to run defrost and ground on passenger side roof. I checked these and they are not there because the Berlina does not have a rear window defrost. your harness coming from back lights also has grounds that run all the way up under dash, or at least i would suspect that at least one carries all the way up front. Its just above air vent on drivers A-pillar, bolted down.[COLOR="Red"] There are no grounds ahead of the drivers side B pillar going to the dash. The grounds are routed under the carpet. I can see the antenna, and antenna wiring go to the rear of the console along with another small wiring harness. I can open that up and check for the 3 ground wires.
I thought it was strange to have three grounds all bolted to different locations within a couple feet of each other, but then i relised that they are not all for lights. One is for rear defrost....grounds to the roof frame another for i dont know what....fuel sending unit and the other probably is for somethong else that i dont know what....running/park, sig/brake and back ups but they are deffinately there. I wonder how many people were left scratching their head with bad grounds but still getting lights on sometimes...lol...once you learn it its somethimg you NEVER forget....lol
I thought it was strange to have three grounds all bolted to different locations within a couple feet of each other, but then i relised that they are not all for lights. One is for rear defrost....grounds to the roof frame another for i dont know what....fuel sending unit and the other probably is for somethong else that i dont know what....running/park, sig/brake and back ups but they are deffinately there. I wonder how many people were left scratching their head with bad grounds but still getting lights on sometimes...lol...once you learn it its somethimg you NEVER forget....lol
Last edited by Charliebates; Sep 24, 2017 at 01:52 PM. Reason: error
