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Chevrolet Blazer Heating and Air Conditioning



  • repairdogrepairdog Posts: 948
    If Auto climate control you have an electric blend door motor also that often fails. Constant cycling of hot to cold. A simply replacement of a $200 part thru the glove box.
  • carprobscarprobs Posts: 1
    I have the exact same problem on my 99 Blazer LT. I discoverd it last fall when I had the AC on and all of the sudden, it would switch over to extreme heat. Then, I realized in the winter when I had heat on, the opposite would happen (AC would kick on). The heat even comes out when I have the fan turned to "OFF." Took it to the GM dealer SIX times last year for the same problem each time and the problem is still ocurring. They replaced the control panel and fan motor. They also said they never heard of the problem and that the system was designed to run on the "auto" function---I told them that I've always used the "manual" settings and never had a problem all these years until now. I even contacted the corporate GM office and they were of no help. If anyone found the fix, please share. It becomes quite concerning in inclimate weather when I go to turn on the defrost and it blows out cold air using the A/C.....
  • repairdogrepairdog Posts: 948
    Post above tells you the common answer. Maybe find another dealer or ask them about the electric blend motor that controls a second blend door on auto climate control LT models - I have a 99 and mine went out and common and it cycles between hot cold even in manual settings. Motor has a cheap plastic gear that breaks.
  • olddocolddoc Posts: 2
    If i can get the dash out and the heater air handler
    exposed can i get to the door near the steering column to repair it without removing the the entire
    heating unit. Any make do fixes that can be done without complete disassembly of the air handler??
    I would welcome a manual wire. My disabled expert
    says the vacum motor is working and he can see it
    move but the door just springs back. The vacum motors behind the glove compartment are ok.
    Obviously i am looking at big bucks that i cannot afford. Any help or suggestions appreciated.
  • repairdogrepairdog Posts: 948
    That air box requires the dash be pulled to get completely out if the internal door is jamming - but have to ask is this an LT with auto climate control (temps on dials and auto positions)? If so there is an additional electric blend motor accessible thru the glove box atop the air box that often fails. If not also look under hood at the drivers side vac lines 5/32" that run to the reservior in the fender and the last T in the system is a plastic line to the heater controls - rotted rubber lines may be causing the door to open then flip back as vac drops due to pressure and default for door is defrost.
  • wnewcombwnewcomb Posts: 1
    My blazer blows constant heat. The heat blows at the highest setting and no matter what I do to the climate control buttons, it still blows even when all settings are turned off. I believe the problem could be the air blend door actuator. I already have the part so that I may replace it, but I can not figure out where exactly the part is behind the dash in order to replace it. If someone could give me a detailed explaination as to the exact location of this part in the vehicle I would appreciate it.
  • repairdogrepairdog Posts: 948
    Are you installing the electric blend motor on an auto climate control with temps in degrees on the dials and auto positions? If so reach up and grab the little tab behind the glove box left side and pull it in then the box swings out and down. Its on top of the heater/AC bow.

    Found some info on another forum and summerized below:
    Remove the vac line that enters and then move the the vac assembly. Remove the electrical connector that feeds the Actuator. With a 7/32" remove the two (2) mounting screws. There is no screw on the back mounting post, just a pin that holds it steady. Pry the Actuator up off the blend door with a screwdriver. Install new one.
  • I have a 1999 Chevy Blazer with the climate control. The problem is with my heat, it never stops. It constantly blows heat out of the vents. I can still change the direction ( defrost, floor, vents) and the speed of the blower, but cannot shut it off. The AC will not come on, the light comes on, but never any cold air, which I am thinking that it has something to do with this. I am looking for any suggestions please. It is hot outside and is unbearable sometimes to drive. Thank you very much
  • I have a blazer with a heater core that got replaced last winter. Since then, it has only blown heat, no cold. It'll switch vents just fine but regardless of where I have the temp dial it only blows hot. The temp dial is just a blue line and red line, no indexed numbers.

    Could it be the temperature dial? I'm not thinking so, but I don't know what voltages to look for to see if its working right.

    I expect it is the temperature (air blend door) actuator, and I *think* I can see where it is. If I understand what it looks like, then if I open the glovebox and move the vacuum controlled actuator I see there, (I believe this one's for the footwell?) then I can look up behind there and see it.

    Is there a way to test the air blend door actuator? Is there a way to get it out without removing the whole dash?
  • The heater in my Jimmy is blowing air out but it's not hot at all. It sucks in the winter time. I just put in a brand new radiator. I had it flushed and everything. Can someone please point me in the right direction?
  • mitch16mitch16 Posts: 11
    My AC only blows hot air. I don't have a automatic climate control system. It's just the standard round dials that you turn for hot or cold. Do I just need new refrigerant?
  • Three days ago, the system have a short circuit and the alarm turn on. Now the short circuit was repaired but three things remains:

    First: when I connect the remote control to open doors then the car open the 4 doors not only one.

    Two: when I connect the lights of the car, the central control of the doors sound like I try to open the doors and is the only way to move the electric mirrors (at the door) to see the sides of the car.

    Three: every time I put the ventilation system in my Blazer LT 2000 the air is very hot, even with air conditioning (probably I need to check this system too).

    Any suggestions... Thanks in advance.
  • I live in WI and it's getting really cold outside. Well when I turn my heat on with the blower on 1 or 2 it blows warm air if it's above freezing if it's below freezing it's cold. Anything on blower 3 or 4 it's always cold. People tell me it's the heater core and to flush it. But when I looked under the hood the hoses from the radiator go to a canister type thing and then that leads into what I think is the heater core. So if I flush it what is that canister thing and will the flush not work then. I tried looking in my manual for a name for the canister thing and can't find a name I can find a pic though. Can someone help me?
  • I live in WI and it's getting really cold outside. Well when I turn my heat on with the blower on 1 or 2 it blows warm air if it's above freezing if it's below freezing it's cold. Anything on blower 3 or 4 it's always cold. People tell me it's the heater core and to flush it. But when I looked under the hood the hoses from the radiator go to a canister type thing and then that leads into what I think is the heater core. So if I flush it what is that canister thing and will the flush not work then. I tried looking in my manual for a name for the canister thing and can't find a name I can find a pic though. Can someone help me?
  • I have looked at all the posts for heating problems. I have a Haynes Manual. It shows how to remove and replace items but in the trouble shootiing there is nothing as to HOW to diagnose heater issues (or how to diagnose so may other things as well.)- just bought the Blazer 2 weeks ago. Replaced a 1992 that was totalled just 3 weeks ago- loved that one..... I could afford the warranty for the drive train - but not for other things- electrical etc.Soooooooo we get plenty of air- blows very hard - have moved all the dials etc- still no heat. What should we check 1st?
    Also.... last Sunday the drivers windshield wiper seemed to go "off track" - it is "spastic" in its actions. the passenger one works just dandy- however they are crossing over and getting stuck on each other- Manual only shows how to change wiper blades. Do the wipers have little teeth that could be eroded like starter teeth and that is making it just not catch all the time- how do I get the wiper assembly off to check? and then what do I do with it?
    Thanks so much.
  • I'm having identical issues as message # 49 - I have replaced my thermostat and checked my coolant levels. I have reduced heat in my system coming out of all air supplies.I'm trying to understand if the coolant flow through my heater core is controlled by a proportioning valve to reduce / increase heat or how it is controlled. My assumptions are that the select heat / cool knob on the front of the dash is a potentiometer but I do not not what it is controlling. Any help would be appreciated.
    Dean Arzberger
  • Hello,
    I just had mine fixed at the dealer (see message #52) as I found out that we DID have a 90 day 3000 mile warranty. It was a spring inside the radiator that regulated the water flow- it would work sometimes and sometimes not- so as we did not fix it ourselves I canot tell you the absolute specific details of the particular spring- I am sure we could have never figured that one out- we thought it was the select heatt/cool knob at first that controlled the baffle that opens the heat. Good Luck.
    :} Anna
  • Anna - Thanks for the information. Was the replaced spring in the main radiator or in the heater core radiator ?
  • Dear toolzz,
    The spring was in the main radiator. The heater core was fine.
  • Anna - May I ask what dealer you took your truck into for repairs ? I live in Waukesha County. I'm at my wits end with this POS. I went to my local mechanic that I trust and he believes it to be a heater core. I don't think it is. I'd like the advice of the dealer.
    Let me know Please
  • I have been trying to troubleshoot my ZR2's lack of heating. ( see message # 53 ) I have found that after the engine has reached temperature 195 deg. and I have the fan on with the heat on ( NO climate control ) I have about 165 deg. on the inlet hose to my heater core and about 109 deg. on the return line from the core.If I take the truck for a short drive I have heat coming out like I usually did. After driving approx. 5 mins. I start to loose heat out of my air supply ducts. Is this a partially plugged heater core ? I only have 58 k miles on the truck . I also noticed that with the truck ideling, the heater on / fan on 2, my A/C compressor clutch was kicking on / off sparatically. After returning from a short drive to test it, the A/C comp. did not kick in. Any help would be appreciated.
  • have read all the threads about the blend door & related. This 98 is on its fourth heater door, the one that directs the heat to the floor or to the defrost or the vents. The temperature is controllable so we know the "blend door" is OK, but we have little or no heat to the floor. It's a $15 part and $485 in labor since the front fender, hood and dash have to come out to replace it. At 10 years of age and 329K miles, it's still a more than serviceable vehicle, if not for this heater issue, but we would rather not dump another $500 into this door deal. I have looked at the schematics and wonder if there is some way to get at that flapper door to prop it up to allow heat to the floor area. I'm hoping that I can identify the lower box on the driver's side and carefully drill a hole that would allow me to stick a piece of coathanger, etc up to get that door up. The door's spindle is probably broken, which is what has been the case in the previous replacements. The vacuum elements are not the issue. I am working from the dealer's schematic put out by ProQuest Automotive EPC and the lower heater box that I am contemplating drilling is, I believe, # 11, in the area over the part that's labeled 14. Any help with this would be appreciated. I'm the 'house' mechanic (resp. for a 69 xk-e, 67 & 81 corvettes ">& 47 Chris Craft), so will understand any directions that are provided.
  • I have a 1997 Chevy Blazer with a heater that only seems to work when it wants to. One day it will work just fine and the next day nothing at all. It gives no warning and I have not heard any unusual's not only the heater, it's cold air too, when I turn it on nothing happens. But I can go out a couple days later and turn it on and it works fine. Any suggestions as to what the problem could be?

  • Hi Toolzz,
    Sorry I've been away for Christmas. It was Pete at Folsom Lake Dodge in Folsom CA.
    :} Anna
  • dfhltddfhltd Posts: 11
    I'm guessing when you say nothing happens you mean the blower doesn't run. If that true the control on the dash for blower speed may be worn out, the wires to the blower may not be making a good connection or the balast resistors may be broken or not making good connection. I suggest when you have the problem you check the voltage at the dash blower speed switch both in and out. The switch connects to the blower and balast resistors which switch in more or less resistance to slow the blower down. Next I would check the voltage at the blower motor. The blower is in the engine compartment. If there is voltage at the motor but it's not runing, check that the motor is grounded by hooking a seperate wire from a clean spot on the frame to the battery negative terminal or you could measure the voltage on the fram. If it's not grounded the frame will have a voltage on it and it should be zero.
    If there is voltage at the control but none at the blower, check the resistors. They stick into the air passage between the blower and the heater core. It should be connected with a plug and I believe the resitors are on a plate that can be removed.
    The blower, resistors and control are all replacable parts.
    Good Luck
  • Ok, so we spent some quality time with the '98. First I went to the local Chevy dealer where the parts mgr was kind enough to give me copies of the exploded diagrams for this heater box flapper/valve/door system. It turns out that the issue for this problem centers on the 'valve' that is on the left side(driver's) side of the heater box. Due to the number of times that this dash assembly has been in and out of the SUV, a small section of the trim around the floor vents was cracked and so, easily removed so that I could see up inside. There didn't appear to be any problems with the vacuum hoses or assemblies. The goal was to get this horizontal door that allows heat to the floor ducts to open up. What the H, I took a pair of very long (straight section about 8 inches) needle nose pliers with a 45 degree angled nose and stuffed the angle part up the ducts to try to push the door open. Guess I was living right... heat on the floor!!!!!!!!! Jubilation only lasted until the next day when the same problem reoccurred. This time after pushing the door up and open, we took a piece of form wire and put a long loop in it, with the diameter of the loop about 3/4 inch. The long length of the loop was so that the raw end didn't get caught on anything and wire was used to be able to shape it to follow the contour of the duct UP to the door/valve. We did not (fortunately) ever have temp problems. The current size of the loop end creates an opening that is ok for heat supply. More supply could be created by making a larger loop end and thus holding the door farther open. You could probably recreate this repair even if the trim is not broken out like ours was; you just need to be able to stuff a loop of wire up the duct to push the door open. We made sure to disconnect the battery while we were working in there, even though it doesn't appear (from the diagrams) that there is anything electrical involved. (Be sure to have your radio reset code). We are guessing that what was happening was that this door was falling down into the opening that it was designed to close off, either through wear or a worn seal. The motor drive didn't have enough power to pull it up out of the stuck position and thus the cheap plastic drive assembly broke. So we saved ourselves a $500 repair bill, but then our house furnace's blower motor died. Guess there's just no winning some days!
  • I have a 2005 blazer and my heater doesn't work it worked fine one day and the next it doesn't can some one please help me out :cry:
  • Recently I had the joy of replacing my heater core in my 1999 Chevy Blazer. After having everything put back in I realized that I had one part and 3 screws left over. Well, after the first cold night I realized that the part I left off was my BLEND DOOR ACTUATOR. So my question is where does it go, how do I put it back in, and can I do it with out having to take the dash board apart again? Please help I have to do as much of my own vehicle work as possible due to the fact I am a preacher so I do not have alot of money.Thanks
  • dfhltddfhltd Posts: 11
    The blend door goes in the duct between the AC and heater core. It flips back and forth to blend hot and cold air even whe the AC isn't running to control the temp. That's wat the actuator does. Yes you probably do have to take the dash apart unless you can get to the place where the actuator goes. In my 96 you can't.

    Go to the parts counter at the dealer and they will copy the pictures and be sure to get the list of the descriptions. They will give it to you for free. You should be able to identify 3 flaps or doors. You should be able to see the one that goes between the hole for AC and heater. The actuator is connected to the shaft of the door and bolts to the duct. The pictures from the parts catelogue will show where it goes.
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