I drove my 94 on a 30 mile trip. When I got in to leave the heater came on & I couldn't shut it off. Where do I start looking for the problem ?

 

I had something very close happen last month.
Being old and lazy, it's hot out, I pulled the blower resistor under the hood and saw that the door inside was closing off the a/c and running thru the heater ducts.

I am still old, still lazy, and it is even hotter. My fix was to put a tounge depressor in to block the door open for a/c and it is working just fine.

When I get younger, less lazy, or the weather gets cooler I will drop the lower dash panel and fix it the right way.

Good luck.

 

Well this is a coincidence. It did it yesterday in my Avalanche truck. Got in to go to work, flipped on the AC and it started to blow real hot. I thought, oh crap, the compressors gone out.

After work got in, flipped on the AC and its back blowing cold air. I figured out then its the regulator temp dial or the trap door sticking. Typical GM. That and lousy cheap electricals.

 

So if I pull the resistor out can I see this door ?

 

I never had to do it but if you do a howto search you should come up with an instruction. If you can't find one I'll see if I can scare up my manual somewhere.

 

just to throw my hat in the ring here, my wife complained that her A/C is only barely cool. I swapped the relays around, and suddenly, it was ice cold coming out of the vents.

Leads me to believe that it was the connections or the relays are life limited. Anyway, it's still blowing cold, and that was a week ago. Now I gotta get another relay just in case.

On my 92 Buick Regal, the 30 amp non resettable "silver" fuse/non resettable breaker popped once.
Just check things, and you can see what's going on.

On my 86 corvette, I wired the heater in the off position by making a link out of a coat hanger, and pushing the heater valve to the closed position, and slipping in the link, and bending it with needlenose pliers so it wouldn't fall out.

It seems that the hard plastic vacuum line that is in the ECM harness broke somewhere in the harness, and I'm not going to unwrap it just to find where it is and remove the whole harness to put in a stainless steel section of tubing so that it can never break in the harness again.

I am thinking of just putting the stainless tubing in on the left side near the steering column, and running a vacuum hose over to the right hand side inside the car.