Top 10 1991 GMC Sierra Questions & Answers

it seems you have a short in either one of the lights or interlock. all are connected to the same fuse. trace the wiring from the fuse box back to the component. Using a test light test in between the wires. check for any obvious breaks in the wiring.

the firing order is
1-6-5-4-3-2

The follwing is a cut and paste from a service bulletin:

Bulletin No.: 461202

Date: May, 1994

SUBJECT:
A/C CONTROL HEAD FLASHES OR ERRATIC OPERATION OF A/C CONTROLS (POLISH
TERMINALS)

MODELS:
1988-94 CHEVROLET AND GMC TRUCK C/K MODELS
1990-94 CHEVROLET AND GMC TRUCK TOPKICK/KODIAK MODELS WITH C60 OR C69 AIR
CONDITIONING

CONDITION:

A/C Control Head flashes, performs erratically or malfunctions.

CAUSE:

Light surface corrosion on the Control Head terminals.

CORRECTION:

Remove the A/C Control Head and while holding the unit with the terminal
cavity down (toward the floor) so no particles will fall inside on the
circuit boards, polish the terminals on both sides of the cavity with a lead
pencil pink eraser. Do not use an ink eraser or other abrasive such as a
small wire brush or sandpaper, etc. Doing so will remove the terminal
coating and degrade the contact surface.

Performing this procedure, in many cases, will make replacing the Control
Head unnecessary. Using this procedure in conjunction with the A/C circuit
diagnosis found in the Electrical Diagnosis Manual and especially before
replacing a Control Head for any reason is recommended.

After polishing the Control Head terminals, but before reconnecting, check
for proper terminal contact as described in the applicable electrical
diagnosis manual. If contact is good, apply dielectric grease (P/N 12345579)
to the harness connector terminals. Please do not apply grease to the
Control Head.

get the oil pressure sender and gauge checked most likley cause is incorrect reading not sudden high oil pressure

It is located just before the evaporator but...

This job requires special tools and special training. If you lack either, you risk SERIOUS personal injury. Injury comes VERY EASILY!

You need to address oil levels, proper and legal refrigerant recovery, system evacuation, and recharge.

You were planning to also replace the receiver/dryer, correct? It also needs the oil in it measured and incorporated into the amount of oil (in %) that would need to be added. FAILURE to address these and other issues will guarantee premature system failure and likely compressor damage.

Take this job to a qualified shop.

Sorry

If it is the factory Delco/GM radio, should work something like this.

Turn the truck on (does'nt have to be running just accesories on), turn the radio power off (turn volume knob all the way left till off, or power button off depending on the radio). I believe there are two buttons on the front next to each other, seek/scan maybe? Press and hold to change the time. One does hours, one does minutes.

No, it does not. I cannot find a cabin air filter listed for a '91 GMC Sierra 1500. Sorry :(

I had the exact problem with my 1993 chevy c1500. I found that the IAC was sticking so the engine would die at idle after warming up and the ignition module was pulsing the ECM intermittently after the engine warmed up so the fuel pump wasn't being turned on after the engine died....I replaced the ignition module and the IAC valve and all is good. I don't know if testing the ignition module reveals that it isn't sending pulses to the ECM.

DL the opertators guide.
its free for allcars.
google it. " 2002 GMC Sierra 1500 operators guide"
that trick works for all cars made,no need to guess.
if your is lost. RTM

You can use Dexron 3 or go to a dealer and get the fluid.