2002 GMC Sonoma heating problem - Truck Repair Advice


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2002 GMC Sonoma heating problem

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Sonoma
Novice

Nov 29, 2011, 12:11 PM

Post #1 of 4 (9687 views)

2002 GMC Sonoma heating problem	Sign In

I have a 2002 GMC Sonoma with the 4.3L V6 and 4-wheel drive with about 75,000 miles. It seems to have developed two problems with the heating system.

The first is the selector switch to change from "defrost" to "dash vents" to "floor", does nothing anymore. It's stuck blowing air out of the dash vents and won't change. I have not tried anything yet, but I was told that it could be the heat/AC module.

The second problem is sometimes it blows warm air and sometimes it just blows cold air. I did notice that this seems to change with engine RPM's. In other words when stopped and idling it's cold and when accelerating it gets warm again. I was told that this could be the blower motor resistor, but that doesn't seem logical since it changes with engine RPM.

Thanks for any help you can provide!
Gary

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 29, 2011, 1:10 PM

Post #2 of 4 (9660 views)

Re: 2002 GMC Sonoma heating problem	Sign In

For the temp problem it sounds like your heater core is plugged up, probably with old Dexcool. Flush the system and specifically the heater core with a garden hose in both directions.

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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Sonoma
Novice

Dec 4, 2011, 3:24 PM

Post #3 of 4 (9607 views)

Re: 2002 GMC Sonoma heating problem	Sign In

Flushed the system and that seemed to help the heat situation. I think the level was low to tell you the truth. Anyway, it puts out good heat now and seems to run a little cooler.

Thanks
Gary

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 4, 2011, 3:26 PM

Post #4 of 4 (9603 views)

Re: 2002 GMC Sonoma heating problem	Sign In

Good job. Thanks for posting the result.

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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

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