2003 gmc 2500hd right turn signal and hazard light problem HELP!&#

jl856 · July 6, 2015

I have a 2003 GMC 2500hd that the right side turn signal front and back are dead. The hazards are dead on the right side front and back also. I have park lights front and back. I have checked grounds, replaced the flasher to the new style, checked fuses, replaced all the bulbs and I still get the fast blink on the right side. When I hook up a trailer it will blink real fast on the right side but the pickup is dead. The trailer has LED lights so I am thinking that there is a small amount of voltage there just not enough to light a regular bulb. The left side turn and hazard works perfect. This has me stumped. Also I have checked the junction block on the rear frame of the truck. I have left blinker power to the block but no right blinker power coming to the block.

Has anyone had this symptom with the multi function switch? Don't know how to test it or if you can.

Any ideas would be greatly appreciated.

Doug_Scott · July 6, 2015

Does your truck have separate signal bulbs from the brake lights on the rear of the truck? If the brake and signals use the same bulb, do the brake lights work on both sides of the truck.

If the signals are on their own, you will want to take a look at the flasher assembly itself. Not sure when the change happened, but, I do know that the 2004 Sierra has a flasher that has something like 11 wires to it, and looks nothing like the traditional flasher of old that I am familiar with. It also runs something like $110CAN for the flasher "box"

LED bulbs do not draw enough power to trip the traditional flasher can. Traditional flasher can uses a bi-metallic strip of metal that will bend when heated by current flow. Electronic flashers use a different system to trigger the flash, and should work with LED bulbs. Inserting a resistor into the signal circuit can trick the flasher so it will slow the flashes down. I think you can also get special LED bulbs that come with the resistor built in on the signal only bulbs.

jl856 · July 6, 2015

This truck does not have signals in the mirror. The OEM flashers had a problem that when you put your turn signal on the hazards would come on and do other weird stuff. The one that I put in is the updated flasher that is suppose to fix that problem. I know that the trailer wires have there own fuses so they must be getting their power from the main feed. I don't have a wiring diagram. Don't understand the trailer wanting to blink fast either because when I check it with a volt meter it shows nothing.

jl856 · July 6, 2015

The truck has separate bulbs for turn and stop and they are not LEDs. Yes the brake lights and park lights work fine on both sides. The flasher has been replaced with the updated flasher. I have checked continuity from front to back turn signal sockets and all is good.

The truck showed no signs of a problem. The problem just started all of a sudden.

jl856 · July 9, 2015

Finally figured out the problem. A mouse had gotten into the fuse box under the hood and had chewed the wire that feeds the right side turn/hazard lights into. This truck doesn't get used all the time and I suppose sitting idle made it fair game.

Doug_Scott · July 9, 2015

Mice (and most other rodents for that matter) seem to really like the covering on wires and brake flex lines. Years ago I had a 4 month old Dodge pickup towed into the dealership I was working at. Customer complained that brakes had failed completely, and he had back into a tree, hard, that morning due to this. Brake pedal went straight to floor, no resistance at all when engine was running. Normally when you have a hydraulic failure in the brake system it only impacts one circuit, either front or rear brakes, or one side of front and rear brake, the other circuit will still function due to master cylinder using a floating piston on the front circuit of master cylinder. This truck upon inspection did not have any flex hoses left on it, all that was left was the metal fittings are each end of the three flex hoses. Heard back from customer about a week later, he had just found a dead skunk under his deck at the cottage, apparently dead from poisoning from eating flex hoses and drinking brake fluid in the process. I know, off topic, but rodents were brought up.

Take a look at all the wiring you can find in engine compartment and make sure the mouse did not have a balanced diet, by eating different colours(flavours) of wires. I have always wondered why the insulation on all electrical wires did not have some chemical that made eating or chewing the wire very distasteful, perhaps some synthetic "Resiniferatoxin". One of those things that cannot cost that much to include, they could promote the idea, and charge another penny a foot. I am sure every woman out there with kids and pets would request that on everything they bought with a electric cord on it.

Doug_Scott · July 6, 2015

The odd part of this is that the trailer lights work(fast flash is due to low current draw, the missing lights on the truck are the cause of that. If you can locate a wiring diagram you could check to see if the trailer signals are getting their feed from a different spot than the truck signals. Not sure why GM would not just run the trailer signals off of the body signals. Can you check the wires at the flasher to see if you can find the signal feed to the right side bulbs on the truck, and also if there is a unique circuit for the right side trailer signals?

Does your truck also have signals in the mirrors? I do not know for sure, but, I think the signals in the mirrors also have their own circuit. My friend with the 2004 Sierra had an issue with the right signals not working, and I am not 100% sure, but I thinjk it was only the mirror that was not working. He ended up changing the flasher to fix it. With both of us being from the old world of auto repair, this made no sense at all. But, that fixed his.

You have said "updated flasher" or "new style" a couple of times, what is the difference between them and the original one?