Question about 1998 GMC Jimmy

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Heater temp control not working

Blows heat all the time no matter where i set temp control,also a/c isnt working

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  • Anonymous Dec 19, 2008

    my heater vent all ways say on the upper front vents even when adjust it i need help 98 jimmy.

  • Anonymous Feb 26, 2009

    blows hot air all the time does not cool when i lower temp

  • brasshorse53 Mar 05, 2009

    i have same problem with my 1998 gmc jimmy will cook you out of the vehicle. don't know how to fix.

  • pimpbones01 Mar 17, 2009

    I even replaced the heater core a year ago. Then as soon as winter came around I found out that some mechanic had bypassed the heater core since it's replacement and no one told me anything. Had they let me know at the time it would've been warrantied service. I still have no heat. Thank goodness it's about to be warm again.

  • Anonymous May 03, 2009

    Blows hot air all the time,1998 Jimmy SLT, is this something to do with the cliamte controls?



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We had the same problem in our 98 GMC Jimmy. Was blowing hot air everywher with everything shut off & air conditioning would not work. We found out it was the Blend Dood Actuator, it is located behind the glovebox. We purchased one on EBay & replaced it and are back on track again. Good luck!

Posted on Sep 10, 2009

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Check the heater core its pronby bad

Posted on Dec 13, 2008


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I've had 2 Astros. A 1993 and a 1994, and had a problem with the heat/AC on both of them. They blew only air through the defroster no matter where I set the control, heater, A/C, floor or vent.

Both times the problem was with the VACUUM hoses in the engine compartment. The hoses had become dry, brittle and then cracked. The hoses are black tubes about the size of a drinking straw, and about 12" to 14" in length. Look for hoses that are hanging loose, they usually break off from junctions where 2 or 3 lines come together.

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