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Chevrolet Blazer Heating and Air Conditioning



  • Have a 1997 Chevy Blazer, my heat will not turn on when i put the switch on at all. Like other trucks it will work when it wants to and then couple days later i will get in it and it will work all on its own any ideas as to what the problem is.

    Thanks :mad:
  • My 1997 Chevy Blazer Compressor Clutch does not get any power when i turn on the A/C in the car...

    What could the issue be?
  • jlflemmonsjlflemmons Posts: 2,242
    Low freon. There is a pressure switch on the side of the dryer (large silver canister near the firewall on the passenger side. If the freon charge is low, the pressure switch shuts down power to the clutch to protect the compressor.

    There are two small round metal and rubber high pressure gaskets about the size of a water hose gasket but thinner that are where the two aluminum tubes bolt to the top of the compressor. These seals can slowly leak causing a freon loss. If you decide to just add freon, use the freon without oil as you haven't lost the oil from the system. If you decide to change the seals, you should have a vacuum drawn on the system before recharging. That way you get all the moisture out.
  • Help,

    My heater only works sometimes. More specifically, the blower works but only blows cold air. When I don't need the heater, it works just fine. The temperature gage occasionally reads high. I have also noticed that sometimes, when the fan switch and the heat/AC/Fan selector switch is turned off, there will be heat coming out of the vents (small amount). When I flip the fan and heater switches on; the air turns cold. When this has happened before I have changed the thermostat. This time a new thermostat did not fix the problem. What else should I consider checking?

  • jlflemmonsjlflemmons Posts: 2,242
    How many miles on the Blazer, and has the antifreeze been changed and cooling system flushed. Very important, this vehicle uses the long life Dexcool antifreeze and cannot be mixed with conventional ethalene glycol (the green stuff).
  • It has 120,000 miles and yes I still use the orange antifreeze. It has been flushed and the heater core was replaced in December.

  • jlflemmonsjlflemmons Posts: 2,242
    Julie, there is an air mix damper in the ductwork under the dash. I haven't had to work in this area, but it does sound like it could be your problem. These vehicles do not have the conventional heater control valve, so water is always flowing through the heater core. Anybody who has done work on this feel free to jump in here. :)

    Curious about the temp gauge, though. When you start from cold, the gauge will go up just above normal for a minute or so, and then should drop back to normal. What this indicates is the point at which the thermostat opens.
  • juliemactjuliemact Posts: 3
    Thanks for your reply, I'll look into the damper. The temperature gauge has been going higher than it normally does, more like it's about to overheat, until I hit the interstate and begin to accelerate, then it lowers back to normal.
  • jlflemmonsjlflemmons Posts: 2,242
    I know this sounds stupid, but are you sure the cooling system is full? Each of the issues you discribed can also show up with air in the cooling system. When you accelerate hard, do you hear gurgling in the area over under the glove box (heater core)?
  • I bought my 2000 4.3L Blazer in 2003 with 38,000 plus miles on it. Since then, I have replaced the heater core, door bushings, front driver locking mechanism, idler arm, shocks, but didn't even bother replacing those poorly made front reclining handles on the driver and passenger seats.

    Now, my A/C isn't puttin out cold air, so I had the shop do a test and refill the freon a couple weeks ago. A week later, there is no more freon, so I take it to another shop. They do a leakage test with dye in the freon and can't detect anything in the engine comparment... and they said it is most likely the Evaporator Core behind the dash... and this will cost almost $1000 to replace. Is this really the problem, or is this shop blowing "hot air"? Also, it is even worth it to replace?

    Please advise.

  • dfhltddfhltd Posts: 11
    First of all it is probably not the evaporator. Are you sure the freon is gone? If it is not, the blend door that mixes hot and cold air may not be moving properly. This is a common problem. Sometimes the actuator fails or the hinge is not working right. Get the parts catelog pictures from the dealer and try to verify the door is moving to the correct positions for heat or A/C.

    Most of the time the freon leaks are from the hoses, O rings and fittings but......

    If you suspect the evaporator, have the freon drained at the AC place and see if you can attach some fittings to the evap inlet and outlet to do a pressure test to see if it leaks. You don't have to take it off if you can attach some hoses or fittings As far as I know the evap. is bolted to the firewall with 4-5 bolts or nuts and can be removed yourself with out getting under the dash. Then you could have it checked with the dye and UV light. If it's bad you could either buy a new one or get a used one from the junk yard that doesn't leak. In either case it's no where near $1000.

    If the evap is OK check to see the clutch to the compressor isn't slipping. When the bearing goes bad after 90,000 miles it ejects ball bearings which get trapped in the clutch until they disintegrate causing the clutch to slip.

    Also you might want to check the receiver-drier. It acts as a filter to the system and if it gets plugged up then the freon dosn't go to the evap as much as it should. They don't cost much and are easy to replace.

    Hope this helps
  • First off.. thanks for the 411.

    I know a few things about cars... but mostly because of whats been replaced... other than that... you don't want me around to help... haha.

    Heres the thing. I took it to one shop just to do a basic test and add freon... and it worked fine for a little bit. I had no need for A/C until a week later, and found it wasn't working. So I took it to another shop, and they did the same tests, and added more freon... this time adding dye to it, and they didn't find any leak in the engine compartment. The shop owner suggested that it was the Evaporator Core and it needed to be replaced... for almost 1k.

    I have a cousin that could help me if I can dial in the primary issues... but don't really know if I should take what the mechanic said as the truth.. or a waste of time. I want to take it to a 3rd place... but these A/C tests run 70 dollars plus every single time.

    What do you think???
  • jlflemmonsjlflemmons Posts: 2,242
    Have them recharge and "soap test" (literally use soapy water) around the top of the compressor where the two aluminum pipes (manifold) connect. There are two little high pressure seals in there that will flatten and leak over time.

    I had this exact same problem on my '99 model. Couldn't find a leak anywhere, and then of all things, my son could actually hear the soft hiss of the leak! Nothing wrong with that kids hearing!

    The seals are about $5-$10 each, takes about five minutes to replace, but then the system needs to be evacuated (vacuum draw down) and recharged. Hope this helps you out. Definitely cheaper (and a whole lot easier) than changing the evaporator core.
  • Hey! Help would be much appreciated from anyone who can help....
    My '99 2DR Chevy Blazer has already had a new water pump installed...just about 5 months ago. About 3 months ago, (during the COLD of PA winter...haha) I noticed that my heater was not working. It seems when I am driving about 55 mph or less, it just will not work, and then the temp shoots up to about 240. However, my drive to work is about 45 minutes, and a good portion of that is on an interstate with a speed limit of 65. When I am going that fast, the temp drops down, and magically I have heat again. When it first happened back in probably January, my husband replaced the thermostat (easy fix) and it worked like a charm until probably about late March. Then the same thing started happening again. Any ideas? I would be very appreciative!!! Thanks!
  • mphrehamphreha Posts: 2
    I have 2000 Blazer that only blows hot air when the AC is on. I tried adding freon, however it seemed to be fully charged as it did not take much at all and continued to blow warm air. I'm thinking there is not a leak since it seems to be under pressure still. Could this be thermostat related? Any thoughts advice woudl be greatly appreciated.
  • jlflemmonsjlflemmons Posts: 2,242
    Others will have more detail, but there is a baffle in the duct work under the dash that regulates the cold/hot mix from the evaporator and heater cores. If you are sure that the freon charge is correct, this may be where the problem is.

    When you say the air is hot, do you mean hot like in ambient outside, or hot as in heater?
  • mphrehamphreha Posts: 2
    I'm pretty sure that the freon charge is correct. We tested the pressure before and it was already in the blue/acceptable level, so we were not able to add much more. The hot air feels more like heater heat and not ambient heat.
  • Soounds like the AC clutch not kicking in as I had same problem and neighbor shows me how to "fix". The is on the right when looking at the engine, it looks like the underside of a oil filter. Anyway it is round and is supposed to spin, when ac kicks on. I guess its an electromagnetic thing which i know nothing about. Anyway just touch it with your finger or a stick real quick and it takes off spinning, at least mine did. So min works like 75% of the time. Every once in a while have to use the stick to get it going. Can you tell I'm not a mechanic? Wonder how much will cost to fix right.
  • jbiljbil Posts: 2
    The heater/AC on my '88 S10 Chevy Blazer blows hot/cold air well. However, when I adjust the selector to any of the AC choices, the air only blows on the floor rather than
    the dash vents.

    I've checked to see that the 2 vacuum hoses are connected to the heater/AC diaphragm on the floor. Maybe the other ends aren't connected.


    1. Could this be the reason that the baffles don't adjust to bring the air to the dash vents?

    2. If so, is there a diagram showing their location on the other side of the firewall?

    3. Is there a handy "how to" cheat sheet to disassemble/reassemble the heating/AC system if it turns out that the diaphragm is bad?

    My Chilton manual is lacking any information on how to troubleshoot this problem,

    Thanks a million,

  • If your compressor is spinning and you have the automatic climate control, see air blend motor/actuator. If you don't find it in the blazer side check gmc jimmy. Its hidden behind the glovebox up and to the left. Did you ever hear a funny clicking from over there?
  • My hubby (the autoparts salesman) says our '92 will need a new condensor, hoses (and some other word I can't think of) to get the air blowing cold again (apparently it's gone beyond just the r-12 or whatever it takes). Anyone know what this might cost?
  • jlflemmonsjlflemmons Posts: 2,242
    '99 Blazer 4dr, 2wd. Great little suv, minimal problems, bought it for my son. but whoever designed the AC system should be flogged.

    It has a very, VERY slow leak. Actually, it had two leaks. We found one and repaired it, the other is yet to be found. My complaint is that the little beast only holds about 32 ounces of R134a freon when fully charged, but if it loses just 4-6 ounces, the compressor starts short cycling and cooling performance drops in half.

    So, every six months or so I have to buy a $7 can of R134A, use 1/2 or less of it, and head on down the road. Not losing any oil, dye doesn't show up anywhere, so we are talking TINY leak, somewhere.

    You could throw major bucks at a problem like this, and never fix it.
  • I have a little problem with my Blazers AC controls. Changing the AC settings between Max, Normal, and Bi-level does nothing as far as changing air flow. No matter which setting it try, the air only blows from the floor and dash vents. Any ideas?
  • I am racking myself trying to finish removing the heater core. I have the entire dash out and removed three bolts under the hood. Are there more? (evidently) How do I get to them?
  • 99 blazer-blower works fine but no warm air. heater core isnt leaking but cant tell by touching hoses if there is circulation. air wont blow through floor but will through vents and defroster. is there a heater control valve or a flap in the air box. whichever it is where is it located- need help with this one-this chevy is about to drive me nuts
  • dfhltddfhltd Posts: 11
    Your 99 probably works the same as my 96. There is no heater shutoff valve. Hot water flows through the heater core all the time. You should feel a really hot hose going into the heater. I think it's the outside hose. You should fix this problem first. Disconnect the hoses and see if they are obstructed. hook up a garden hose to the core and see if water flows through it freely. Try heavy doses of radiator cleaner and force water through the core in the reverse direction. Replace the thermostat. It's cheap and easy to replace.
    As for the rest. There is a flap that controls if air comes from outside and the AC evaporator or the heater. The actuators go bad. sometimes the bearing doesn't work and the flap rubs against the housing. If the hot water is going through the core and the air is cold this is the problem. There are other flaps for the defroster and the floor. Verify they move and if not determine if the actuator or the control is not working. There could be a damaged or disconnected control vacuum hose. I suggest going to the Chevy dealer and get photocopies of the duct and heater - AC which they will give you for free. It will help you locate the flaps and actuators.
  • Same problem as posting #95. My A/C broke and the heater core started leaking both within a short period of time on my 95 Blazer, 177K miles. I bypassed the heater core (I live in South FL) and I replaced the A/C compressor/drier/expansion valve and recharged the freon. So now the A/C is cold, but blows only from floorboard and dashboard vents. Mechanic checked the vacuum tube, said it is OK, said the problem is in the vent system. The vents make a hissing noise (very annoying), but I'm not willing to take it to a mechanic for another $500 repair bill, but if I can disassemble the dash and replace the problem part, I'll give it a try. Or maybe the A/C - Vent - Heat control switch has failed?
  • I have the same problem, my posting is # 100. I'm thinking that it's either the control switch or one of the vent doors has broken. Did you ever resolve your problem?
  • dfhltddfhltd Posts: 11
    I'm not sure if there is a question in #100. The vents are controlled by a flapper is the only way to describe it. They move by an actuator whch has a small gear with teeth. Either the the teeth are striped or the shaft for the flapper has jammed or the actuator doesn't work. I'm told the teeth being stripped or the shaft being stuck is most likely. If the teeth are stripped there is a reason like the flapper is stuck, so you may have two problems in one. The actuator may be turning and the plastic against pastic sound may sound like hissing. I'm not sure. Hissing could be air under pressure going past a partially open flapper. Like I said in the previous suggestion , get the Chevy dealer to make you a copy of the parts manual pictures showing all the parts (get the parts list that goes with it). The parts list will tell you what's what and that way you can find the flapper location that isn't working.
  • I just ordered my second one of these
    1 "ACDelco 15-72182 A/C And Heater Vacuum Control Valve"
    Misc.; $53.27 ... dealer wanted $900 to install ... $95 for part... Price @$50.

    Its a bear to get at bascially behind dash near the ashtray area screwed to the AC duct work... There are two screws on the backside of the valve that hold it in place... I nipped the mounting tabs on first one I installed so I can more easily replace it .. good thing I did ... these units get sticky and cause wierd air flows ... expect scars... lots of sharp edges in side the dash
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