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Chevrolet Blazer Heating and Air Conditioning



  • jlflemmonsjlflemmons Posts: 2,240
    Check the vacuum lines running from the intake manifold over to a tee near the brake vacuum booster and on to the vacuum resevoir in the left front fender. Very common for these to rot and leak with age, and will cause the symptoms you have described.

    Good luck
  • Guys my WIFE'S 2002 blazer has no heat .. i pulled the return heater hose and NOTHING.. one side is hot and the other nothing( its a little wet but no running water)... ???? can I use a air line to maybe blow the core out??? or is it to late and i have to replace it......????
  • jlflemmonsjlflemmons Posts: 2,240
    Backwash it using a garden hose, just don't crank the pressure up too high. Get garden hose repair fittings and install them on heater hoses a couple of feet long. One will be larger than the other. Hook the supply side hose to the "exit" tube on the core, and the drain side to the other. I *think* the smaller one is the supply side, but not sure.

    Gently turn on the water and watch for crud to come through the drain side. Once it starts flowing freely, let it run until the water coming through is clear.

    Put everything back together and get the system flushed and refilled with fresh Dexcool. Do not try to switch to standard antifreez unless the whole cooling system is flushed until the drain water is drinkable! (just kidding, but it needs to be completely flushed) Those two types of antifreeze will not play together, and even a little bit will cause problems.

    With a little luck, the corrosion will not have eaten through the heater core.
  • Issue: no heat. A/C works fine, blower works fine, but it seems when I turn the temp control knob, it turns too easily. I understand there is a baffle that the knob controls to reroute from A/C to heat, but not sure where it is or how to get to it. My thermostat is fine, but going to replace it anyway, along with a new radiator cap. Have not completed a coolant flush, am scheduling that in the next couple of weeks. I also heard it might be some sort of relay switch, located under the hood near the firewall? Any assistance?
  • dfhltddfhltd Posts: 11
    The first thing you should do is go to the dealer and get them to copy the diagrams from the parts catelog. There are acouple of them that show different views. Also get the pages which list the parts and description that go with the diagrams.
    this will help you find the baffels or doors (3) that control airflow and the parts that control them. Check the hoses at the firewall going in and out of the heater to see if they are hot.
  • Hello I have a 1997 Blazer. The heat didnt work when I got it. I direct wired the blower to the batt and the motor was fine. I replaced the switch that operates the fan speed and it worked for a week. Now it only works sometimes. If I hook a direct connection to the fan fan it always goes on. Also I noticed that the heater doors dont appear to be working I can only get defrost and some heat out of the bottom. are these electric or vaccum? I live in upstate NY ( 14 degrees here today )so I really need the heat and defrost any suggestions?

    Thank You
  • Hello I have a 1997 blazer. I took it to get it inspected but because I installed a new battery and only drove 40 Miles it mech. said it wouldnt read it yet. I have since put on 140 miles and 2 days ago the check engine went on and stayed on for the afternoon. The next day it was off and hasent been on since. I brought it back for th einspection and again it read " computer not ready to read) Can anyone tell me why or what I can do. I need an inspection. Please note I took it to a friend of mine who has one of these hand held computer checks and he said it didint show any errors that I should be fine. This was BEFORE my return to the shop for inspection.
  • I have plenty of heat. The problem is it only blows out of the vents no matter what position the switch is in. I replaced the control panel but the problem remains.
  • jlflemmonsjlflemmons Posts: 2,240
    Check the vacuum lines from the intake manifold, to the tee near the brake booster, to the vacuum resevoir in the drivers fender behind the underhood fuse box. These lines rot and since the controls are vacuum operated, they won't work.

  • My girlfriend owns a 1998 Chevrolet Blazer....She was told recently by a mechanic that if you don't use your A/C much, it could actually harm your engine. Is this true at all ?

    I would appreciate some help on this. Thanks so much.
  • tidestertidester Posts: 10,110
    I've never heard that before and don't know how it's possible but maybe someone else can offer some insight.

    tidester, host
    SUVs and Smart Shopper
  • dfhltddfhltd Posts: 11
    Whoever told your girlfriend that is nuts. AC takes power from the engine just like the alternator, the power steering and the transmission and wheels. The AC is no different. That's what the engine is there for. Engines in cars made without AC do just fine. There is no way that not taking energy from the engine is going to hurt it.
  • steverstever YooperlandPosts: 39,958
    In the old days, you were supposed to run the AC a few minutes a month all year round. As I recall, this was to keep the seals flexible (in the compressor I guess).

    Nowadays the AC will kick on when you run the defroster to dehumidify the air, so you shouldn't find anything in your manual about running the AC. And I don't see why never running the AC would hurt anything.

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  • jlflemmonsjlflemmons Posts: 2,240
    Has nothing to do with harming the engine. But you should run the ac or defroster at least once a month for a minute or so to keep the seals lubricated and the oil moving across the moving parts of the compressor.
  • dulinaadulinaa Posts: 10
    Try looking straight down the firewall from where the a/c lines enter it. Do you have any condensation on the ground at all? Is the front floor carpet wet? There isn't much room for any kind of sloshing around. I have had heater cores with trapped air make that sound, especially the chevy trucks. And on my in-laws Jeep Cherokee, that drain was plugged bad, but it was inside the square tube subframe that extends from the firewall, couldn't get to it to blow shop air up to clear it.
  • dulinaadulinaa Posts: 10
    It will not harm your engine, BUT it can ruin you a/c by not running often. Its got the Use it or lose it policy. Your a/c system has lubrication oil mixed with and circulated by the refrigerant. The seals can dry up and crack, especially the front shaft seal on the a/c compressor, causing all the refrigerant to leak out.
  • steverstever YooperlandPosts: 39,958
    I just downloaded a '98 Blazer owner's manual and I don't see anything in there from GM advising owners to run their AC at any time. It may have been an issue in the old days but I don't think it must be a problem now; otherwise the manual would say something.

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  • jlflemmonsjlflemmons Posts: 2,240
    Running the compressor is an issue in any automotive system. It may not be mentioned as most folks will use there defroster/defogger during the winter, and thus run the compressor.

    It may not be as big an issue with R134A, but was definitely an R12 issue. Most systems now days use very, very little refrigerant. As an example, the S10 series Blazer/pickup uses less than 28oz of R134A!
  • steverstever YooperlandPosts: 39,958
    edited June 2010
    I think the long term trend in cars is to lessen required maintenance as much as possible. So my feeling is that the engineers have improved the seals so that there is little risk of failure by not using the AC. Plus as you say, the AC comes on with the defrost.

    Then again, I suppose the manufacturers know that most people trade cars every 3 to 5 years and so they don't mention maintenance for marketing reasons, since many (most?) of us don't want to maintain things. But both my cars are over 10 years old and I just use the AC or defrost as needed, not on some "monthly" schedule.

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  • I own an 04 Blazer LT with 4WD and the heat was blowing cold. The mechanic received a code indicating the thermostat needed to be replaced. They also replaced and winterized the antifreeze, etc. That was on Thursday. On Sunday it was again blowing cold.

    I felt it was a partially clogged heater core but they replaced the thermostat which seemed to resolve the issue for about 2-3 days.

    Any suggestions and should the dealer do the repair free of charge for not fixing it initially?
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