Heater not working

Tiny
ROGER543
  • MEMBER
  • 1998 GMC JIMMY
  • 200,000 MILES
My heater won't change from vent to floor to defrost. So I looked at the vacume lines and they have oil in them. Could it be that the vacuum actuator switch on the transfer case is no good, assuming that where all my vacuem connect to?
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Sunday, April 7th, 2013 AT 12:22 PM

54 Replies

Tiny
ASEMASTER6371
  • EXPERT
No, the vacuum connects to the motor. do you have vacuum to the control head?

This guide can help

https://www.2carpros.com/articles/car-heater-not-working

Roy
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Sunday, April 7th, 2013 AT 4:07 PM
Tiny
WALLT0KW
  • MEMBER
  • 1998 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 189,000 MILES
Any suggestions why heater blows cold air. Coolant is fine. Thanks
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
BLACKOP555
  • EXPERT
Feel the heater core hoses when the vehicle is hot and engien off.

What do the hoses feel likke?

Both hot? Both just warm?

One hot one cold?

Neither hot?
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
APOLLOBMORELOS
  • MEMBER
I thought my heater core was going bad, but before I decided to replace it I took both hoses off and got my air compressor and blew air thru the heater core (both ways, in and out)to unclogged something in there and it works, now I got heat.
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
FTROOP73
  • MEMBER
  • 1998 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 125,000 MILES
Im only getting high heat out of car vents no matter what I select on climate control selector. A/C works but its just not blowing cold air into vehicle. On heat selection, I cannot control heat either. Could it be blend-door broken or stuck in heat mode, or the blend-door motor failed, or climate control selector failed?
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
RASMATAZ
  • MEMBER
This sounds like the temperature door actuator is not working. I would remove the actuator and try moving the pivot for the door by hand here is a guide to help you see what I am talking about.

https://www.2carpros.com/articles/replace-blend-door-motor

Here is the location on your car.

Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

Cheers
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
JUSTJULES1234
  • MEMBER
  • 1998 GMC JIMMY
  • 112,000 MILES
Hi

We have a jimmy and the heater blows, just not hot air. Would that be a hose?
Is it a cheap fix?

Thank you
julie
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
RASMATAZ
  • MEMBER
If its not hot enough-check the thermostat, heater core and air blend door/actuator
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
JUSTJULES1234
  • MEMBER
Lol thanks.I have no clue how to check those things, ill ask a friend to
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
BRASSHORSE
  • MEMBER
  • 1998 GMC JIMMY
Heater problem
1998 GMC Jimmy 6 cyl Four Wheel Drive Automatic

I am having a problem with my heater which has an automatic temp control and it isn't really working. It either blows really hot air or none at all. The air conditioner doesn't work now, either. Chevy garage said it is the automatic temp control auctuator or something else. He wants over $1,000.00 to fix it. I can't afford that, so has anyone else had this same problem and know for sure what is wrong? One person said it is probably the blending door. If it is one of these, how do you know where they are and what do they look like? Please help! Thanks in advance, brasshorse
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
DEWEYG
  • MEMBER
Blending door is behind glove box(small release top left, bend down spring loaded tab then lower glove box.) Door is on right. Plastic gear can sometimes break. Can epoxy or replace or could be vacuum line has leak. Check vacuum first by disconnecting line and turn your climate knob from cold to hot(or vise versa) if you feel vacuum on your thumb then probably your gear
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
HAROLD HOPPS
  • MEMBER
  • 1999 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 143,000 MILES
Dont get any heat form my 1999 gmc se jimmy 4.3 liter air cond. New antifreeze fan works heater coil is ok no heat
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
JDL
  • EXPERT
Does the engine reach normal operating temp? Are the heater hoses hot? Does the blower motor work? Just some things to check.
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
MULLETM
  • MEMBER
  • 1996 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 210,000 MILES
I have changed the thermostat and it is still not operating at normal engine temp - it runs cool. I have no heat but the vents work fine at all levels. Any suggestions?
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
MERLIN2021
  • EXPERT
Try warming the Vehicle, then carefully feel the heater hoses, are they both hot? If one is cooler than the other, You need to flush the core, or do a replacement job on the heater core. Also if the system has a heat control valve on the heater hose, make sure it is working! Also check the thermostat, and the temperature blend door, thats under the dash, in the heater plenum. You can flush this yourself, buy the prestone flush kit and install the tee in the heater return line. Disconnect the heater hose at the waterpump, clamp the hose in back of the tee you installed and back flush till it runs clear.20 mins or so. As far as running cool is it a low reading on the gauge? Or have you used a thermometer in the radiator?
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Thursday, October 4th, 2018 AT 11:10 AM (Merged)
Tiny
WILLIAMTOBIN1
  • MEMBER
  • 1996 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 17,000 MILES
Put selector over to hot and get no heat with heater, defroster, etc. Just cold air. One mechanic stated it needs a new intake gasket? Another says that it may be burning radiator coolant and need a new head gasket. Both cost $$$$. Any sugesstions?
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Thursday, October 4th, 2018 AT 11:11 AM (Merged)
Tiny
RASMATAZ
  • MEMBER
Check the thermostat could be stuck open and also for a clogged heater core
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Thursday, October 4th, 2018 AT 11:11 AM (Merged)
Tiny
MISTY ROBINSON
  • MEMBER
  • 1999 GMC JIMMY
  • 4.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
While driving last night my heater just stopped working blower and all.
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Thursday, October 4th, 2018 AT 11:11 AM (Merged)
Tiny
HMAC300
  • EXPERT
Check fuse and relay under hood fuse box first then check for harness burnt up between heater control and blower resistor by blower.
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Thursday, October 4th, 2018 AT 11:11 AM (Merged)
Tiny
LDBJ123
  • MEMBER
  • 1996 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 60,000 MILES
I replaced the thermastat but I still don't have heat. Once in awhile I get luke warm heat for a little while. Any ideals?
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Thursday, October 4th, 2018 AT 11:11 AM (Merged)

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