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One Brake Light not working


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thejuggla1
New User

Sep 24, 2009, 1:13 PM

Post #1 of 2 (2517 views)
One Brake Light not working Sign In

GMC Suburban 94

I went to add these LEDs tail lights(They are basically a clear Lens upgrade with LEDs on them, they go over the stock bulbs) and I wired my left one in fine, it works properly. I went to wire my right side THE SAME WAY and when I went to check the brakes my right one doesn't work, the LEDs don't come on, but the left side works fine.

The weird thing is the turn signal works fine however the brakes and the turn signal use THE SAME WIRE(I dunno if it is like this for all vehicles, but that is how it is on mine) so I am so stumped, I checked the fuse box, tried disconnecting the LEDs, switching the stock bulb(Check it with like 3 different NEW bulbs.) and no luck, can anyone help me out here?


DanD
Veteran / Moderator
DanD profile image

Sep 24, 2009, 2:33 PM

Post #2 of 2 (2507 views)
Re: One Brake Light not working Sign In

Are you sure that the right brake light was working before you began this project?

The way this thing is wired; the brake light switch (single white wire) when activated sends power to a portion of the signal switch. With the signals off, this power is fed to the yellow (left side) and green (right side) brake/turn signal switch’s internal contacts and then on back to light the bulbs. When the signal is click for right turn the green wire brake contact is switched open and now the green wire is fed power via the flasher unit; by a different contact inside the signal switch; causing the bulb to flash.
With you saying the right side will flash; that tells us that from the signal switch to the right rear, the wiring, socket, bulb and ground for the circuit is ok. The left brake is working; so we know the brake switch is ok and power is getting to the signal switch’s brake light contacts or at least to the left side contact.
Without being there to test the circuit myself; I would suspect the signal switch is at fault. The contact inside the switch for the right brake light circuit may be burnt or corroded open?
Go to the base of the steering column and you should find a flat multi-wire connector for the signal switch. Find the green wire for the right rear. Use a test light with the right signal turn on; will be the easiest way to find the proper wire; it will/should be flashing the test light.
Turn the signals off and actuate the brake light switch; this green wire should now light the test light on solid; if not replace the signal switch.

Dan.

Canadian "EH"










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