A/C Temperature Control

JERRYLMO

MEMBER
CHEVROLET BLAZER

My Blazer is a 2001 4DR, 4WD, 4.3L V6, Auto with 136,000 miles on it. I'm the original owner.
About a week ago when I turned on the A/C, if you barely turned the temp control (center knob) to warm up the air coming out the vents it got hot instead of just tempering the air. Now, it just stays hot all the time. The compressor is running and there is proper refrigerant level in the sytem. I took the fan resistor off the evaporator box and looked in to see if the motorized damper door was doing anything. When you turned the temp control to full cooling it moved about an inch towards blocking off the airflow to the heater core and stopped. When you turned it to full heat it moved back to the "full air across the heater core" position. Any ideas?
Thanks. Jerry

4 Replies

BOOTDOG

MECHANIC
665 POSTS

Either something is wedged, not allowing the door to close all the way, or the actuator is going bad.

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Wednesday, July 11th, 2007 AT 11:14 AM

JERRYLMO

MEMBER
27 POSTS

When the fan resistor is removed it's possible to see in there. My wife got me one of those lighted bore scopes last Christmas and I might be able to see something causing a hang up.
If power is removed from the actuator motor and there's nothing physically preventing the door from moving, is it possible to move the door or does the gearing on the actuator motor prevent that? Thanks.
Jerry

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Wednesday, July 11th, 2007 AT 12:55 PM

BOOTDOG

MECHANIC
665 POSTS

I would remove the actuator before trying to force the blender door shut. Just to be on the safe side.

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Wednesday, July 11th, 2007 AT 3:51 PM

JERRYLMO

MEMBER
27 POSTS

Turns out it was the blend door actuator. Still a pain in the neck to get to it, but I got it. On the actuator there are what appears to be three mounting holes for screws. There are two screws toward the inside of the truck are relatively accessible but the one on the back was pretty much impossible. I took some of the bolts loose on the HVAC box so it would come away from the firewall. I tried getting a socket on it but never could seem to get it. After fooling with it for about 30 minutes I just reached up there and pulled it up and it popped right off! There isn't a screw back there just a locating pin. I doulble checked the new part and it responded to the temp control setting turning all the way CW and CCW. Got it all back together and now I have A/C again! Thanks for your help and advice. Jerry

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Friday, July 13th, 2007 AT 11:02 PM