I have a strange problem where I periodically get cold air from the heater. I have tkaed the Blazer to both a repair shop and the dealer and neither can find the problem. Of course, it does not happen when I bring it in for service.

Today, when it is 85 degrees outside and the engine is at about 200 degrees, I cannot get "heat".

Any clues or suggestions?

Thanks

 

First, you have to duplicate the problem. When it is there (not blowing any heat) make sure the engine is at full operating temperature, the gauge will be just below 210 degrees F. Then, feel your heater hoses where they go into the firewall (attatch to the heater core) they should both be hot and about the same temperature. If the one on your right (closest to the driver's side is alot cooler than the other one, The heater core is restricted (plugged up). You can usually (at least temporarily) fix this by back-flushing the heater core. Take both hoses off at the heater core and flush it out with a garden hose until you get clear water coming out. If both of the hoses are hot, Your temperature door is probably not moving. You can see this by lowering your glove box and looking at the electric actuator on top of the heater case. When you move the temperature selector the shaft of the motor should rotate (key On).

OH yea! welcome to the site!!

 

Just signed on today and your post helped me alot. Must be my temp ****. I just pulled the vac hose off and I got heat. The problem has seem to fixed itself. ?? I guess the temp **** controls the amount of vac to the acuator.
thanx again

 

You also might have another problem. Trans fluid in the vac lines. There is a TSB at the dealer about fluid in the lines causing HVAC problems since they all use the same switch as the source of vacuum. This switch is located on the transfer case and has 3 lines to it. If it is caught in time you can save your controls if not then you have to replace them since the dealer has no way to clean the fluid out of them at the present time. This switch also supplies vacuum to the 4x4 acuator under the battery box for 2HI - 4HI operations.

 

I have an '01 Blazer, could this be the same problem. I checked the switch behind the glove box. Pulled the vac line and cycled the actuator a few times. It seemed to work for a while and then went back to blowing cold. Now I pulled the vac line to make it stay in the same position. Other symptoms are air blowing from the vents no matter the setting on the control ( ie. defrosts, floor, etc). Could the AC fail on ? How do I know if the compressor is running?