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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), GMC Mechanic
Category: GM
Satisfied Customers: 29457
Experience:  GM Grand Master Technician 2007. 14 years experience.
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1997 chevy suburban: heater control

Resolved Question:

1997 chevy suburban the AC doesnot blow out the vents like it should like it's stopes up somewhere we tried changing the thermostat controls on the front were u turn the unit of and on and set temp but this did not change any thing I would like to know what to look for in the dash to try and solve this problem I also noticed the heater control valve did not have a vacuum line on it and both sides of the hose where hot going into the heater core would this cause the problem I'm having the truck also has rear AC and the low side line from the accumulator is never that cold but the accumulator and the other low side lines are ice cold and dripping rear vents blow hot for a wile the blow cool but not cold also the front blows a little cooler help needed
Submitted: 6 years ago.
Category: GM
Expert:  GM Tech (Cam) replied 6 years ago.

Greetings and Welcome to Just answer.

There is an actautor on the drivers side of the heater controls above the dash that controls the actual door positions. It has a couple of rods attached to it. See if that moves. If not then you likely need to replace it. See also if the rods have come loose.

Customer: replied 6 years ago.
Do u have a diagram or more detail on how to get to it what to move to get to it and what about the heater control valve
Expert:  GM Tech (Cam) replied 6 years ago.
Object Number: 258020  Size: SH
Customer: replied 6 years ago.
Would this be the only thing you think would cause the problem and what about the heater control valve problem
Expert:  GM Tech (Cam) replied 6 years ago.

This does not have any affect on the rear. The rear is likely an actuator to control the door.


Customer: replied 6 years ago.
One last question is the actuator for the front vents the same for the rear or different and where can I find it
Expert:  GM Tech (Cam) replied 6 years ago.

The rear has its own systen in the right rear of the vehicle.


Customer: replied 6 years ago.
The front lower actuator is moving in both directions What do u recommend checking. Now
Expert:  GM Tech (Cam) replied 6 years ago.
Take it off and move the actuator by hand to see if you can get proper operation. IF not then you have an issue in the heater assembly itself.
GM Tech (Cam) and 5 other GM Specialists are ready to help you
Customer: replied 6 years ago.
When u say heater what do u mean and give me a diagram
Customer: replied 6 years ago.
Can u still help me im still. Having problems When u say heater,system do u have a diagram or a idea on what and where to check

Expert:  GM Tech (Cam) replied 6 years ago.
In an hour. I am driving home.
Customer: replied 6 years ago.
Can u help me now
Expert:  GM Tech (Cam) replied 6 years ago.

I do not have a clear diagram of the rear system. The actuators are behind there and are vacuum controlled.

For the front, what I mean is the actuator moves, but does it move all the way? I have my doubts so if you take the actuator off the heater box and move it by hand, you can tell if it is moving or geting stuck on something. I honestly think something has fallen down the vents and is causing the door not to move fully or the door is broken inside and causing this.


Customer: replied 6 years ago.
Ok when u say heating are u talking about the same actuator
Expert:  GM Tech (Cam) replied 6 years ago.

Yes, the same actuator in the rear changes from hot to cold. It is a door that this actuator moves.

The same goes for the front. The actuator, a single actautor changes from hot to cold, and a different actautor changes the mode from floor to vent to defrost.


Customer: replied 6 years ago.
Whre is the one that changes from hot to cold in the fro t
Expert:  GM Tech (Cam) replied 6 years ago.

Behind the glove box.


Customer: replied 6 years ago.
Which motor would make the front vents blow harder also the heater control valve is missing a vacuum would that cause any problems