Re: HOW DO U REPLACE THE TEMP BLEND DOOR HEATER ON A 1999...
Remove the center console. around the ash tray, the cig-lighter,the radio...the radio just slides out when you stick a small, little slot-head screw-driver in the little slots to release the clips. All the wires unhook and are easy to disconnect and reconnect.. There are screws in the back where the radio was ... remove all the plastic anchor screws and pull out the screws and the anchors...When all the socket screws are removed, take out the control assembly for the HVAC... pullback the entire center console...you will be able to reach up and remove the little plastic enclosed motor assembly that controlls the door...remove the three screws and you have the motor that operates the door...Hind-sight-My cost for the motor assembly was $65.00...I thought that was the solution to the problem...After you remove the assembly, CHECK THE DOOR OPERATION ...I attempted to operate the door and a cracking plastic sound resulted in a completly destroyed duct work area where the motor assembly attached...now I have to replace the door assembly in the duct area, way up there in the dash...I recommend makeing sure that the door operates.. and there is no obstruction causing the door to be stuck,...which caused the damage and breakage of the motor assembly. Before buying the replacement part.
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Do you know if the radiator is full of coolant ? Does the gauge on the dash show the engine temp to be cold after you run the engine ? Could be the thermostat is not closing. If the heater hoses are getting hot, could be a blend door problem under the dash.
OK IF BOTH HEATER HOSES ARE HOT IT HAS TO BE A BLEND DOOR MOTOR PROBLEM YOU NEED TO FIND THE BLEND DOOR MOTOR UNDER DASH MOVE TEMP KNOB BACK AND FORTH. SEE IF BLEND DOOR IS MOVING IF NOT MAKE SURE YOU HAVE VOLTAGE. IF SO REPLACE BLEND DOOR
check your blend door, center of the dash at the bottom remove black cover, its above the white stepping motor, the motor turns the door with temp selection, when the door breaks you have no control over temp selection, check the stepping motor (white square box), by removing it and plug it in, and turn the temp knob does the motor turn, if not verify power in the plug and replace motor, if so use an inspection mirror and look at the bottom of the blend door (where motor mounts) see if it is broken. If the door itself is broken, this is a large repair, you will have to remove the entire dash from left to right to access the environmental station which is where the blend door is located. Hope this helps, let me know
The temp blend door, or blend door actuator may be faulty. You can check this by watching the movement of the blend door actuator while you turn the temp selector knob. If the actuator is working, then it may be the blend door, or blend door lever broken. If these are ok then the control head may be faulty.
Your '99 Blazer does not have a water valve. Just a temp. blend door. In other words, hot water should be flowing through the core at all times. Like the other techs said, make sure you are getting the whole system full of coolant. You might even try disconnecting one hose, and pouring water into the heater core itself. On most of these year models, if you listen, you can hear the rush of water through the core when you lightly rev the eng. I have replaced 3 heater cores just last year on '96-'99 Blazers. They clog easily. YOu can blow or flow water through them, but if they don't flow freely, I mean without any restriction whatsoever, they will not get as hot as you want. The thing is tiny!
Here's an easy test: Run engine until temp gauge reaches normal: around 180-200 degrees. Reach back to the firewall and grab both heater core hoses. Are they both about the same temp. and HOT? THey should be. If one is much warmer than the other. You are clogged enough to suffer in the winter. And from what you said: "Brrrrrr" You are getting poor performance out of your heater.
BE sure to check that the blend door is working. Is it cool when you set temp to cool? Blazers go through way more heater cores than they do blend doors, so I'm betting your core is either empty, or clogged. TaterTodd