How do you find a short in backup lights on a 97 GMC p/u?

Question

The backup lights and turn signals are on the same fuse which pops when you drop it in reverse. Pops so quick, I can't find the problem. All wires are in the original looms, no bare wires I can find. Thanks.

Answer 1

These can be very difficult to find as I did this for a living for a very long time. I read the other answers and the one guy that said wiring in a headlight across the fuse holder will enable you to have a live circuit will help if you know what you are doing. Cutting wires without cause is a last resort and I would never recommend that. To start the short is obviously in the reverse lamp circuit from the neutral safety switch on the side of the trans. to the rear somewhere. I have found that most of these problems reside in the fact that there is usually a trailer wiring package installed either by the factory or by someone else. I would give a long and lasting inspection under the truck where the wiring loom runs the length of the left frame rail to be sure you cannot pinpoint something here. The problems with trailer wiring or other shorts is generally close to the spare tire area. You might have to drop the tire and get into this area to expose it all. There is a lot of mud and crud in here and there have been cases I found that the wires simply corroded together. So do a thorough inspection of this area. Also inpsect the trailer plug if it has one as I have found plugs with shorted pins inside. As you can tell, I believe you have to look and look some more to find your problem. Good luck.

Answer 2

Wire a spare headlight into the fuse slot for the one that's blowing.It will light up if there is a short. Now you can work on a live circuit a least. Pull the tail lights assemble out as they can be bad for wire rubbing in behind. Other than that it a wire trace to pin point. Did you inspect the bulbs really good as i have had a few bulbs or sockets short inside(plastic sockets are bad for burning out the grounds)If you can unplugged any connection on the way back to the tail lights if the headlight goes out the short is behind that connection. Good luck hope I helped

Answer 3

Your going to need a wiring diagram to be able to tell which wire is for your back-up lights. As a licensed mechanic I would rarely go looking for the short in a circuit like this. I would find where the back up switch is located and cut the feed wire there and run a new wire to the back of the vehicle joining up where the wire feeds the lights at the rear. I would of course have confirmed that the short wasn't in the rear light sockets or that the wrong bulb hadn't been installed in the back up light socket.