Any mechanics out there?

[Sonoma]

I am having trouble with my 2002 GMC Sonoma pickup. No heat at times. Warm when I accelerate and cold when idling. I was told that this might be a plugged heater core, so I am going to try and flush the system and see what happens.

Also the selector switch stopped working; it's stuck on dash vents and won't change to either the defrost or floor positions.

Any ideas would be more than appreciated, I hate to take it the dealer if it something I can repair!

Thanks

 

[MLeeK]

Weak idler pulley, loose belt. You will also have heat when you let off gas but are turning a corner. Blower will also blow harder when the RPMS are higher.

Not plugged heater core. Would be very little to no heat or air velocity at all time.

WHENEVER you have no heat for any reason make sure to check that your antifreeze/coolant level is full before anything else.
The selector switch is a manual slide type switch or electronic? Slide type break in the dash and no longer move the part that changes things. Electronic have a relay/fuse that blows.

We own a used dealership and repair shop too.

 

[GeorgieGirl]

Leak in your radiator.

 

[Big Mike]

I'm not a mechanic but I've had my fair share of auto heater problems.

First thing is to make sure that your coolant is filled and still the proper consistency (if it's too watery it might freeze, too think and it could gel). Are you running standard anti-freeze or Dexron? If you are going to flush it, it might be a good idea to switch to regular. The Dexron is supposed to be good and last a long time...but I've heard plenty of bad things about it. I had a 2001 Blazer and when I had engine work done, they suggested switching to regular (green) coolant. But you do have to flush out all the old stuff though.

If you can find them and get to them, there should be a hose going to and from the engine to the heater core. When up to operating temp, those hoses should be warm/hot. If they are cool, then it's like you have a leak (or a circulation problem).

If your selector switch has stopped working, maybe your heat selector is out of whack as well. Not sure what to tell you on that one. On my blazer, we had to replace the heater core because it started to leak...had to dismantle the whole dash and when it got put back together, the heat selector didn't work anymore. My father-in-law did the work, so I don't know if or what got missed.

 

[Rephargotohp]

Mike, Dexron is transmission fluid so definately don't put that in your Radiator.

Also check for a bad Thermostat, Sometime when they are shot they wll open partially with higher RPM but shut when there is not the fluid pressure, They should remain open at temperture not flow

 

[Big Mike]

Sorry....my bad. It's DEX-COOL...not Dexron.

 

[Sonoma]

Not plugged heater core. Would be very little to no heat or air velocity at all time.

WHENEVER you have no heat for any reason make sure to check that your antifreeze/coolant level is full before anything else.
The selector switch is a manual slide type switch or electronic? Slide type break in the dash and no longer move the part that changes things. Electronic have a relay/fuse that blows.

We own a used dealership and repair shop too.

First thing is to make sure that your coolant is filled and still the proper consistency (if it's too watery it might freeze, too think and it could gel). Are you running standard anti-freeze or Dexron? If you are going to flush it, it might be a good idea to switch to regular.

Thanks for the advice!

I think it may have been low on fluid causing the heat/no heat problem. I went ahead and flushed the system and I have more heat than ever before and it seems to be running cooler that before also.

As for the selector switch it is electronic. I was told by a body man it could be the AC/Heat module.