How do i fix my tail light on a 1994 suburban don't work but brake lights and headlights do do?

Answer 1

You need to isolate the problem.

Since your tail lights don't work, check the dash lights. Are they out too? If so it could be a fuse. Check the fuses to see if you've blown the one that controls the tail lights. If you HAVE, you need to find out why. Often a trailer plug can be shorted causing the fuse to go. If you have a plug for the trailer lights, get under the back, unplug it and bypass the trailer plug. Note that the tail light wiring harness in the back has an assembly that allows you to plug in a trailer connection.

If the fuse is good, start with a meter and work toward the front. Does the truck have side clearance lights? Do they work?

Do the front clearance lights/parking lights work?

If you're getting dash lights but no tail lights or clearance lights, check the headlight switch. It has several outputs, one for headlights, one for clearance and tail lights and one for dash lights which can be dimmed. If ONLY the clearance/tail lights are failing to work, make sure the switch is functioning properly. To do that, pull the 4 screws around the dashboard bezel, then carefully pull the bezel toward you. The switch assembly is on the left, don't disconnect it yet.

Get a good volt meter or test light and start probing around. You should see an input and output wire for the headlights, they will be larger than the others. Verify that you know how to test the power output by connecting the meter with the negative to vehicle ground and the positive to the connector or lead that you're testing.

Next, test the input for the dash, tail and clearance lights. If the fuse is good you should be able to find the appropriate voltage on the input line and the voltage should be present when you turn on the parking lights on the output line. If you DON'T have voltage on the output with the switch on but you DO have voltage to the input. it's the switch. Amazingly, they aren't too expensive from the dealer.

There are lots of possibilities, you just need to find out what's wrong, and DON'T just start throwing parts at it. KNOW what's wrong before you replace anything.

Which is what I did, costly! What I did below and the fix!

I have the ANSWER for BRAKE LIGHTS NOT WORKING & TAIL LIGHTS on 1994 Chevrolet Suburban when all other remedies FAIL! My nightmare experience went through every part replacement I could think of, Bulbs, new tail light circuit boards, relay, in dash head light switch. Even had a mechanic tell me the problem was going to be in the steering Column wiring harness which connected to all of the other electrical areas of the truck. Made sense and there was a ribbon of about 20 wires heading up the column from under the dash. I'm getting 12 volts at the rear circuit board contacts when I press the brakes but no LIGHT from the bulb. So after the mechanic messed up my steering column replacing the wiring harness the problem remained. What I didn't catch was the reading on the volt meter was negative 12 volts. A reverse polarity problem which will happen when?