HVAC Temperature Probs
10-19-2016, 10:24 AM
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HVAC Temperature Probs
Hi all this is my first post on the forum I have a 2004 (2004.5 I believe as it is Manufactured in March 2004) 2500 5.9L QC 4X4 SLT.
Now on to the problem, AC and Heat both work and work good at all speed of the fan on at all position (defrost, Floor, Vents, Etc.) the problem is that when you want to adjust the temperature make it warmer or colder the temp does not increase or decrease. You either have heat or ICE COLD A/C. if you turn the **** all the way in one direction (heat or A/c) it will change to where the **** is at but I have no intermediate temperature control.
any help thank.
Now on to the problem, AC and Heat both work and work good at all speed of the fan on at all position (defrost, Floor, Vents, Etc.) the problem is that when you want to adjust the temperature make it warmer or colder the temp does not increase or decrease. You either have heat or ICE COLD A/C. if you turn the **** all the way in one direction (heat or A/c) it will change to where the **** is at but I have no intermediate temperature control.
any help thank.
10-20-2016, 11:29 PM
#2
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Welcome to the forum.
I suspect you have broken blend doors, an issue that comes up on the 3rd gen forums.
On these trucks coolant flows through the heater core full time. Temperature control is achieved by a pair of blend doors that direct a portion of air through or around the heater core in proportion to the temperature selected.
A stepper motor drives a coupler, that drives the door. Tabs on the HVAC case and on the couplers are supposed to stop the motor from pushing the doors too far. The tabs can fail and cause the doors to break. I think there was an updated part number for the upper and lower case.
Replacing the doors or couplers generally involves removimg the dash, draining coolant, and evacuating the AC system. Not complicated, but time consuming.
A company called heater treater makes metal replacement doors and apparently has instruction on cutting into the HVAC case to avoid removing the dash.
This thread might be helpful.
https://www.dieseltruckresource.com/...rstood-210483/
I suspect you have broken blend doors, an issue that comes up on the 3rd gen forums.
On these trucks coolant flows through the heater core full time. Temperature control is achieved by a pair of blend doors that direct a portion of air through or around the heater core in proportion to the temperature selected.
A stepper motor drives a coupler, that drives the door. Tabs on the HVAC case and on the couplers are supposed to stop the motor from pushing the doors too far. The tabs can fail and cause the doors to break. I think there was an updated part number for the upper and lower case.
Replacing the doors or couplers generally involves removimg the dash, draining coolant, and evacuating the AC system. Not complicated, but time consuming.
A company called heater treater makes metal replacement doors and apparently has instruction on cutting into the HVAC case to avoid removing the dash.
This thread might be helpful.
https://www.dieseltruckresource.com/...rstood-210483/
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