Tail light troubleshooting advice
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Junior User
Joined: Nov 2013
Posts: 75
Likes: 3
From: Cypress, TX
Tail light troubleshooting advice
When I started working on my truck neither of the turn signals or brake lights for the tail lights worked. I have since replaced the brake pressure switch, and a blown fuse in the fuse box. Now I have the passenger side brake light and turn signal working on the tail lights. Drivers side will not come on either occasion. I was thinking maybe a ground issue, but did some quick sanding to try and get a good ground with no luck. I have not check continuity of the wire yet, and am offshore, so I dont have my truck readily available. Was wondering if anyone had ideas for a common cause, or quick fix to this problem? Anyone had the same issue? Thanks, Matthew.
New User
Joined: Jan 2008
Posts: 19
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From: snowville va.
tail light trouble shooting
I ran into a problem with mine when I was putting it back together and had two problems first I had a bad connection at the firewall plug. Also signal lights would not work right unless all lights are hooked up front and back. Check these and hopfully problem can be fixed.
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Junior User
Joined: Nov 2013
Posts: 75
Likes: 3
From: Cypress, TX
I unplugged the firewall connection, had a quick look, then plugged it back in. It seemed to be in alright shape, but cant be certain it was working. I was thinking that since I had one brake and turn light working for the tails, that the problem could be a bad ground on the drivers side. I thought I checked the front turn signals too, but cant be certain. I will have a look at those when I get home. Thanks.
Tuned
Joined: Jun 2013
Posts: 289
Likes: 4
I unplugged the firewall connection, had a quick look, then plugged it back in. It seemed to be in alright shape, but cant be certain it was working. I was thinking that since I had one brake and turn light working for the tails, that the problem could be a bad ground on the drivers side. I thought I checked the front turn signals too, but cant be certain. I will have a look at those when I get home. Thanks.
I developed the exact same issue over the weekend -- passenger side rear brake and turn signal worked great but lost the driver's side rear brake and turn signal. I checked the wire continuity from the light assembly all the way up to the firewall plug and all checked out fine. From under the dash, I started at the fire wall plug and worked backwards towards the dash/steering wheel. I have identified a short in a wire between the firewall plug and the steering wheel harness. I have not pinpointed the exact lcoation yet but if I move that section of wiring harness i get the drivers side working again.
Hope that give you some guidance.....
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
MC Do you have a circuit tester like this one
There are 3 wires coming to the rear from the front. I like to start at the rear verifying power or not, then moving forward. There is a factory connection just off the end of the drivers side frame rail, test it and you will know if you need to go to the front.
Does not effect all trucks but some have to have the ign switch turned to on for the brake lights to work, so have the sw. on.
Brake lights are split because of the turn signals on the same wires. The tails (all) are on the 3rd wire.
guluk
John
There are 3 wires coming to the rear from the front. I like to start at the rear verifying power or not, then moving forward. There is a factory connection just off the end of the drivers side frame rail, test it and you will know if you need to go to the front.
Does not effect all trucks but some have to have the ign switch turned to on for the brake lights to work, so have the sw. on.
Brake lights are split because of the turn signals on the same wires. The tails (all) are on the 3rd wire.
guluk
John
Fleet Mechanic
Joined: Oct 2007
Posts: 1,972
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Check the front turn signal grounds.
Also every time I unplug something I put a dab of dielectric grease on the plug before I reconnect it.
Also every time I unplug something I put a dab of dielectric grease on the plug before I reconnect it.
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Cargo Master
Joined: Jul 2006
Posts: 3,014
Likes: 91
From: Concord, CA
Interesting in that my driver's side has one issue. Always the driver's side.
My tail light works but not the brake light. It is not the bulb. It is not the socket. It is not the harness as it is new all the way to the firewall.
My tail light works but not the brake light. It is not the bulb. It is not the socket. It is not the harness as it is new all the way to the firewall.
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Lead Gopher
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From: Seattle
That is interesting because, at least on my trucks, the wires come down the drivers side to the back corner then across the back to the passenger side. Seems the problems would be at the end of the line, not somewhere in the middle, unless it affected both sides.
I've had some issues but for me it was always the ground. The housings themselves not being grounded well. I removed the screws that hold the housings in place and wire brushed them and put back together and that seemed to do it. My continuity meter was showing no continuity between housing and bodywork.
The one guy mentioned the harness between firewall and steering wheel. For automatics and 3 on tree at least there should be a sleeve that goes up inside the column from the bottom where the wires come out that is to prevent chaffing of the wires. An insulator. I can take a picture of that later if it is of any interest. Not on 4x4 trucks which used the different steering column, at least.
On this web page it mentions "Don't forget to slide the protective sleeve up your new harness into position behind the column clamp."
http://mongrelmotorsports.purpleflyi...umnSwitch.html
I've had some issues but for me it was always the ground. The housings themselves not being grounded well. I removed the screws that hold the housings in place and wire brushed them and put back together and that seemed to do it. My continuity meter was showing no continuity between housing and bodywork.
The one guy mentioned the harness between firewall and steering wheel. For automatics and 3 on tree at least there should be a sleeve that goes up inside the column from the bottom where the wires come out that is to prevent chaffing of the wires. An insulator. I can take a picture of that later if it is of any interest. Not on 4x4 trucks which used the different steering column, at least.
On this web page it mentions "Don't forget to slide the protective sleeve up your new harness into position behind the column clamp."
http://mongrelmotorsports.purpleflyi...umnSwitch.html
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