Heater problem
Thread Starter
CF Beginner
Joined: Dec 2018
Posts: 1
Likes: 0
Heater problem
I have a 2008 Chevy express 3500 6.0 that gives me uncontrollable heat or no heat at all. If I try to turn the heat off it keeps blasting full bore. Fan speed changes as it's supposed to, can switch from defrost to face to feet no problem there.
Turn the heat on while driving nothing happens, pull over and switch engine off and restart sometimes the heat will work.
Turn the temperature **** while driving no response. If it gets too hot sometimes I'll pull over turn everything off restart and it will stay off, to get the heat going again I have to pull over switch to high heat and restart engine and then I may get heat again. I'm thinking its vacuum related .
Any1 have any ideas?
Turn the heat on while driving nothing happens, pull over and switch engine off and restart sometimes the heat will work.
Turn the temperature **** while driving no response. If it gets too hot sometimes I'll pull over turn everything off restart and it will stay off, to get the heat going again I have to pull over switch to high heat and restart engine and then I may get heat again. I'm thinking its vacuum related .
Any1 have any ideas?
Super Moderator
Joined: Feb 2017
Posts: 6,207
Likes: 689
I think the temperature **** is electric and it controls the servo motor actuated blend door.
You should be able to find the schematics here: Search Wiring Diagrams
I would check voltages at the **** and the connector to the HVAC assembly. Also make sure the door is moving freely.
You should be able to find the schematics here: Search Wiring Diagrams
I would check voltages at the **** and the connector to the HVAC assembly. Also make sure the door is moving freely.
CF Pro Member
Joined: Jan 2015
Posts: 898
Likes: 11
From: West Coast
I have a 2008 Chevy express 3500 6.0 that gives me uncontrollable heat or no heat at all. If I try to turn the heat off it keeps blasting full bore. Fan speed changes as it's supposed to, can switch from defrost to face to feet no problem there.
Turn the heat on while driving nothing happens, pull over and switch engine off and restart sometimes the heat will work.
Turn the temperature **** while driving no response. If it gets too hot sometimes I'll pull over turn everything off restart and it will stay off, to get the heat going again I have to pull over switch to high heat and restart engine and then I may get heat again. I'm thinking its vacuum related .
Any1 have any ideas?
Turn the heat on while driving nothing happens, pull over and switch engine off and restart sometimes the heat will work.
Turn the temperature **** while driving no response. If it gets too hot sometimes I'll pull over turn everything off restart and it will stay off, to get the heat going again I have to pull over switch to high heat and restart engine and then I may get heat again. I'm thinking its vacuum related .
Any1 have any ideas?
Have a look at the vacuum schematic. You can see the heater control valve there. This was just recently discussed in a prior thread.
Last edited by dberladyn; Dec 20, 2018 at 11:26 AM.
Trending Topics
Super Moderator
Joined: Feb 2017
Posts: 6,207
Likes: 689
from GM ...
2005 GMC Truck Savana
Air Temperature Actuator The air temperature actuator and auxiliary air temperature actuator are a 3 wire bi-directional electric motor. Ignition 3 voltage, ground and control circuits enable the actuator to operate. The control circuit uses a 0-12 volt linear-ramped signal to command the actuator movement. The 0 and 12 volt control values represent the opposite limits of the actuator range of motion. The values in between 0 and 12 volts correspond to the positions between the limits.When the HVAC control assembly sets a commanded, or targeted, value, the control signal is set to a value between 0-12 volts. The actuator shaft rotates until the commanded position is reached. The module will maintain the control value until a new commanded value is needed.
Air Temperature Description and Operation
HVAC CONTROL COMPONENTS
Air Temperature Actuator The air temperature actuator and auxiliary air temperature actuator are a 3 wire bi-directional electric motor. Ignition 3 voltage, ground and control circuits enable the actuator to operate. The control circuit uses a 0-12 volt linear-ramped signal to command the actuator movement. The 0 and 12 volt control values represent the opposite limits of the actuator range of motion. The values in between 0 and 12 volts correspond to the positions between the limits.When the HVAC control assembly sets a commanded, or targeted, value, the control signal is set to a value between 0-12 volts. The actuator shaft rotates until the commanded position is reached. The module will maintain the control value until a new commanded value is needed.