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GMC Jimmy Heating and Air Conditioning Problems

My jimmy just started blowing cold air at idle and slower speeds, but when I get up to higher speeds (50mph) or more it blows warm or hot air. I also noticed that my 4 wheel drive don't work either, not sure if these problems are related.

Clueless and not a mechanic,



  • Any problems with your A/C ... talk about it here.
  • Ok here is my problem. Its going to sound very strange. A/C works decently at night. blows around 60F. During the day im lucky to get 65F. The strange thing is, The higher the fan speed ... the hotter it blows. the lower the fan speed the cooler it blows. I checked the compressor levels, i have everything in the green on both high and low side. All my pipes going to and from compressor/accumulator are cold and sweating. Anybody have any ideas ? Could my A/C be sucking hot air from somewhere ? IM totally stumped. Any ideas are welcomed.
  • jglongjglong Posts: 1
    My '03 Trailblazer constantly reads inaccurate actual outside temperature. For example, here in Oklahoma we've had 30+ days of 100 degrees or higher, but my Trailblazer never reads more than 50 degrees. Consequently, my A/C sucks.

    What do I need to replace/check?
  • repairdogrepairdog Posts: 948
    Never said year but yes the recirc door could be stuck or actuator bad. If you have climate control there is also a blend door - with AC problems I go to the shop after checking connectors - too many interlated problems. But also check the vac hoses under hood on drivers side for rot - the lower one Ts off )plastic one) to the AC.
  • repairdogrepairdog Posts: 948
    There is a temp thermistor believe up by the radiator (is on Blazers) that feeds the readout and if bad or way out of cal will screw the AC up.
  • My 2000 Jimmy (97K miles) heat does not work. Only ambient temp air blows out. A/C works fine. Checked temps on all Radiator hoses and hoses going in and out through fire wall. Temps from 130 - 200 degrees. Thus, some heat should come out. Checked with vacuum gage that the all vent doors worked. No apparent problems. Pulled front dash off and can see the blender door motor pin rotates when the temperature adjuster is turned from hot to cold and back. No change in air temp though. The amount of air flow does decrease when changing temp knob from cold to hot. Thought is the blender door is stuck or broken. However, getting to the blender motor looks like a challenge. Any advice on what the problem may be and what to do next.
  • I have a problem with my Jimmy. When I turn on my ac the ac compressor turns on but there is no air coming out of the vents. Sometimes the air will blow for the first 3 minutes when I turn on the ac but it will always turn back off and I can still here the compressor on. Anybody heard of this before?
  • Sorry, sounds like the classic clogged heater core so no water flowing thru it - have to flush and hope it doesn't leak or blow a hole - another Blazer defect, oh did I say that - Dex cool should be flushed evetry 3 years min and any air in the system it gels up. Search on clogged heater core and I've posted the flush several times. Good luck cause the heater core is dash out and over $500. No help after 5/75 or so by GM but if before for others they pay half if you ask for zone to review.
  • Take it an AC shop and have them look at the R134 level, could be low, the pressure switch bad, or a loose connector. Not easy without AC gauges to find. If 97 and over 80-90k miles the compressors blow the front seals, another GM quality part so get a NEW compressor, not rebuilt or it will die within a year.
  • Last spring the A/C was only putting out a little cool air so I bought a can of R134 w/leak detector and everything was fine. This fall after using the heater for a couple of weeks the weather got warm again, A/C isn't cold again. Put in another can of R134 w/leak detector, cleaned around hose connections and compressor, no leaks found. Stayed cool until we used the heater again. Anyone have any ideas?
  • Something is very wrong with my 98 Jimmy's climate control. It keeps going back and forth between hot and cold and it sounds like it is changing back and forth between recirculating and bringing in fresh air. Even when I turn the dial to off, it continues to make the sound like it is switching back and forth. Anybody have any ideas?
  • If the auto climate system with temps on the dials then you have an additional electric blend motor that swings the heat air door to maintain the temp and it has a plastic gear that can get stripped and if your battery died recently can get lost or not know where it is so searches. Dealer can reprogram or replace and I suggest them as most other shops have not done these and it actually runs much more.
  • Yeah, one of the battery terminals had worked lose just before it started happening. Thanks a bunch
  • When I started my '95 Jimmy yesterday morning the heater fan was on and blowing, so I turned it off until the car could warm up. When I went to turn it on again the fan didn't come back on. No noise, no fan , no nothing. I checked the heater fuse and replaced it, but no luck. Any ideas?
  • Probably the fan motor died - cheap part to replace from underhood and believe only 3 small bolts - all stores sell them. Also possible fan resistor mounted by AC box but thats speed control so fan should still be on at some speed.
  • My 2000 Jimmy stopped blowing air. I have heat and defrost, just no air movement. I'm not sure where the blower motor or blower motor resistor are located. On this model they seem to be hidden by a sealed black plastic shroud that must be cut open. Is the motor resistor located within that black plastic shroud or is it mounted somewhere on the firewall?

    Thanks in advance.
  • jnohrjnohr Posts: 2
    My 2001 Blazer just suffered the same fate. How do we get to the fan motor?
  • repairdogrepairdog Posts: 948
    Resistor is under that plastic cover - cut to access. The fab motor is accessed underhood on pass side.
  • mkobmkob Posts: 10
    I have a 99 GMC Jimmy with 122k miles, this vehicle has never had a/c problems up until 2 days ago. Our temp outside is 96 and when I went to use my a/c it blows warm air. I checked the charge and it is fine, all hoses are in great condition and fan is working. I kept running the a/c trying to figure out what the issue was and finally after 17 minutes the cool - not cold air came out. What could be the reason?
  • repairdogrepairdog Posts: 948
    Pressure switch problem or loose connector (check one on rear of compressor under the air intake) or the comp is leaking or clutch is failing.
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