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Low heat blowing out the vents

august41august41 Member Posts: 3
edited November 2016 in GMC
I have a 2000 gmc jimmy. Here's the issue I am having getting luke warm air through my vents, about 95 degs. w/ outside air temp. below 50 deg,. when the outside air temp. is above 60 deg. then I get hot air through my vents, about 115 deg. The heater core been replace, new temorstate, new antifreeze, new blend door motor. When selecting floor, dash or defrosts controls works fine, so I believe my vacuum lines are ok? Blower motor works fine when selecting low / high speed. Bleed the coolant line for air after changing out the antifreezes. I am completely stump can anyone help?


  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    edited November 2016
    So have you modified the radiator or added an oil cooler? Have you noticed worse than normal fuel consumption?
  • august41august41 Member Posts: 3
    I have not modified the radiator nor add any oil cooler. I am getting worse then normal fuel consumptions.
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    It sounds like you are over-cooling as you have all the symptoms, but I can't think of why at the moment. Is it possible to get a direct reading of coolant temperature somehow? Mechanic's thermometer, scan tool, etc?
  • august41august41 Member Posts: 3
    I finally had some time on my hands and again flush out the heater core, radiator, and all the lines. When I flush out the heater core I used a 5 gal. bucket and clear tubing to catch anything if anything that was clogging up the heater core (did not use a bucket last time) I did notice I had some rust like practical's at the bottom of the bucket that came out from the heater core. Also since it was pretty new antifreeze I used a filter when pouring the antifreeze into a gallon jug to dump back into the radiator and notice the same thing, little pieces of rust like particles and what look like sand particles. Could I have gotten a bad batch of antifreeze? I used dex-cool.
  • ember_darkstarember_darkstar Member Posts: 1
    Similar issue as to previous person: I have a '95 GMC Jimmy and have been unable to get proper air flow out of the air vents. I have been told that my issue are the air flow control doors within the vents. I've been looking on line for videos/instructions on how to replace them. Anybody know how to do this?
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    You might try THIS VIDEO. It's not the same year as yours but same generation.

    Here's another VIDEO that might help you.
  • rickmnrickmn Member Posts: 19
    The temp on both heater hoses should be close to the same. If one is hot and the other much cooler, that would indicate a low flow problem. If they're both hot, then I would suspect a blend door or actuator problem. You'll have to locate the blend door actuator and change the temp on the dial while you watch to see if the actuator is opening and closing the blend door.
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