20 Most Recent 2004 GMC Sierra - Page 8 Questions & Answers

Turn the key on but don't start the truck.Push the gas pedal to the floor 5 times, then turn the key off.Some models will do it with 3 instead of 5.

Usually when one side is hot and the other is cold, and each side is controlled separately, the problem is a blend door not working. The blend doors are usually controlled by small electric motors.You might research "blend door" online and see if anything pops up.

tail light prob just globe. Brake lights check fuse, brakelight switch, globes in that order

Three additional things that can cause overheating - a restricted exhaust system, a weak fan clutch, and restrictions in the cooling system in the block or hoses. Any chance you might have air in the cooling system ?

A number of things to check--fuses and brake light switch etc. Got a manual for this vehicle?

He hasn't replaced it the way I read it. If you interrupt power to it by cycling the key it trys again and may get stuck at cold. The "mode" ie floor, defrost, etc is the one you can see from the driver's side floorboard up under the dash. It has a big white gear meshed with it's output, can't miss it. The passenger's side hot/cold motor is on the bottom of the heater case, closest to the floor. The driver's side hot/cold motor can be seen through the glove box hole if you open the box and look through the hole. You can't fix the motor, you will have to replace it. They are between $150 and $200. You can replace the mode and the passenger hot/cold motors with minimal work. You may have to pull the entire dash off to get to it. At the very least you will cuss alot to fit your hands into the hole to replace it...

The wiper relay is stuck in the open position. This relay location can be found in your owners manual and it will most likely start working if you tap it lightly, regardless to keep it from happening again, replace it. Not positive on it's location on your truck but usually in the under hood fuse box passenger side rear. Hope this helps.