1995 C1500 HVAC Temperature Valve (Blend Door)
March 5th, 2014, 5:14 PM
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1995 C1500 HVAC Temperature Valve (Blend Door)
Folks,
New to the forum but have already done a ton of reading on this here (thanks!) and I seem to have found my problem, which leads me to other questions... If this ends up in the wrong section of the forum let me know where I should post it.
My HVAC unit is wanting to blow mainly hot air after a recent setting to Defog/Full Heat yet I know the AC is fine. The Mode Door appears to be working as the airflow changes properly from Windshield Outlets to Dash/Floor to Dash Only.
The Temperature Blend Door (Valve) actuator is working as I can hear and see it move but when its control is switched to Full Cold it seems like it doesn't move very far before I hear some 'squeaking' like noise from inside the HVAC assembly and it stops its travel. Like something is jamming it.
I have recovered a few bits of hard rubber seal from the floor outlets which looks like they may be part of the Mode Door 'wiper strips' I've read about here that degrade and break off the door. I'm wondering if a similar thing has occurred to the Temperature Blend Door and something is jamming the door from fully closing and letting the air bypass the heater core.
Has anyone been in there? Not sure what the Temp Door looks like. If I remove its actuator will I be able to see the door inside the HVAC Assembly or will I just see a pivot rod sticking out of the HVAC?
Looks like I need to remove a good portion of the lower dash (bolsters/ashtray/glove compartment) to get in there. What fun. If the door needs replacing it looks like the entire assembly needs to be removed for disassembly - ouch!
Hoping someone with more experience on the internals of the HVAC assembly can chime in here as it's definitely unexplored territory for me! Just to be clear, this is the Temperature Blend Door and not the Mode or Recirculation Doors.
Thanks!
Barry
New to the forum but have already done a ton of reading on this here (thanks!) and I seem to have found my problem, which leads me to other questions... If this ends up in the wrong section of the forum let me know where I should post it.
My HVAC unit is wanting to blow mainly hot air after a recent setting to Defog/Full Heat yet I know the AC is fine. The Mode Door appears to be working as the airflow changes properly from Windshield Outlets to Dash/Floor to Dash Only.
The Temperature Blend Door (Valve) actuator is working as I can hear and see it move but when its control is switched to Full Cold it seems like it doesn't move very far before I hear some 'squeaking' like noise from inside the HVAC assembly and it stops its travel. Like something is jamming it.
I have recovered a few bits of hard rubber seal from the floor outlets which looks like they may be part of the Mode Door 'wiper strips' I've read about here that degrade and break off the door. I'm wondering if a similar thing has occurred to the Temperature Blend Door and something is jamming the door from fully closing and letting the air bypass the heater core.
Has anyone been in there? Not sure what the Temp Door looks like. If I remove its actuator will I be able to see the door inside the HVAC Assembly or will I just see a pivot rod sticking out of the HVAC?
Looks like I need to remove a good portion of the lower dash (bolsters/ashtray/glove compartment) to get in there. What fun. If the door needs replacing it looks like the entire assembly needs to be removed for disassembly - ouch!
Hoping someone with more experience on the internals of the HVAC assembly can chime in here as it's definitely unexplored territory for me! Just to be clear, this is the Temperature Blend Door and not the Mode or Recirculation Doors.
Thanks!
Barry
March 6th, 2014, 6:38 PM
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Folks,
Well it looks like it may be the Temperature Actuator (the motor that changes the position of the door) and NOT the Temperature Valve/Blend Door itself!
After removing the Ash Tray and Glove Compartment for access (visual and tool) and observing the operation it became apparent that with the blower on high the actuator did not have enough 'umph' to move the door from the Heat to Cool position. It works fine moving from Cool to Heat and, with the blower off, it worked fine in BOTH directions. The test I did in my initial post was with the blower off so I could 'hear' the motor & door move and the lack of airflow is what gave me proper results.
Looks like when the door moves from Cool to Heat it is doing so 'with' the airflow through the HVAC which assists the motor greatly in moving the door. Moving from Heat to Cool goes 'against' the airflow making things somewhat harder. Chevy appears to have spring-loaded the door towards the Cool position to help with this but if the actuator is 'weak' and the blower is on high it may not be enough.
I'll replace the Temperature Actuator and let you know where things go from there but I think I've found the problem...
Barry
Well it looks like it may be the Temperature Actuator (the motor that changes the position of the door) and NOT the Temperature Valve/Blend Door itself!
After removing the Ash Tray and Glove Compartment for access (visual and tool) and observing the operation it became apparent that with the blower on high the actuator did not have enough 'umph' to move the door from the Heat to Cool position. It works fine moving from Cool to Heat and, with the blower off, it worked fine in BOTH directions. The test I did in my initial post was with the blower off so I could 'hear' the motor & door move and the lack of airflow is what gave me proper results.
Looks like when the door moves from Cool to Heat it is doing so 'with' the airflow through the HVAC which assists the motor greatly in moving the door. Moving from Heat to Cool goes 'against' the airflow making things somewhat harder. Chevy appears to have spring-loaded the door towards the Cool position to help with this but if the actuator is 'weak' and the blower is on high it may not be enough.
I'll replace the Temperature Actuator and let you know where things go from there but I think I've found the problem...
Barry
March 13th, 2014, 3:11 PM
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Folks,
Well that was it. Looks like the motor had gotten too weak to move the Blend Door from Heat to Cold with the blower on. With the blower off it could make the transition. All looks good now. So glad it was not a problem with the Blend Door itself inside the HVAC box!
Barry
Well that was it. Looks like the motor had gotten too weak to move the Blend Door from Heat to Cold with the blower on. With the blower off it could make the transition. All looks good now. So glad it was not a problem with the Blend Door itself inside the HVAC box!
Barry
March 18th, 2014, 6:05 PM
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Richardx2,
Glad to help. I use several forums like this for DIY stuff and if you can weed out the junk (usually not to difficult) they can save you BIG $ on things like this. There appear to be three (3) 'actuators' that control the HVAC Doors/Valves on our 1995 C1500 trucks. The following would be for those vehicles optioned with the 'Three Rotary ***** / Two Push Buttons' HVAC Control Heads and would not apply to any HVAC system (cable operated sliding levers?) that may have been a base option. I've seen a couple of parts lists for the latter and the set-up is indeed different.
The Mode Door Actuator (Vents/Floor/Defrost) is on the extreme left side of the HVAC box near the steering column. Access is tight but with the drivers side 'Knee Bolster' trim panel removed it's accessible. It's used to move a couple of doors in the HVAC box so it has a couple of linkage arms attached to it that also need to be looked at before assuming the actuator is at fault.
The Temperature Valve Actuator (my issue) controls the Cool/Heat position of the HVAC and is behind the ash-tray assembly, which needs to be removed for access. Again, tight but manageable. Appears to be the exact same actuator the Mode Door uses - it just lacks the additional 'linkage' attachment the Mode Door utilizes.
Last is the Recirculation Actuator that controls the 'Fresh Air / Interior Recirculation Air' function of the HVAC box. This appears to be on top of the HVAC box underneath the top of the dash and must be a JOB to get to! Seems to be a different actuator than the Mode and Temperature one. Sure hope it doesn't fail as replacing it appears to be a REAL challenge!
The good news is, at least with the Mode and Temperature actuators, that (with the appropriate trim panels/fascia removed) you can pretty easily observe their operation to see if they're working or not. The Recirculation Actuator seems to be another kettle of fish entirely!
Barry
Last edited by Barry A. Waters; March 18th, 2014 at 6:18 PM.
September 15th, 2016, 2:12 AM
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help!
Folks,
Well it looks like it may be the Temperature Actuator (the motor that changes the position of the door) and NOT the Temperature Valve/Blend Door itself!
After removing the Ash Tray and Glove Compartment for access (visual and tool) and observing the operation it became apparent that with the blower on high the actuator did not have enough 'umph' to move the door from the Heat to Cool position. It works fine moving from Cool to Heat and, with the blower off, it worked fine in BOTH directions. The test I did in my initial post was with the blower off so I could 'hear' the motor & door move and the lack of airflow is what gave me proper results.
Looks like when the door moves from Cool to Heat it is doing so 'with' the airflow through the HVAC which assists the motor greatly in moving the door. Moving from Heat to Cool goes 'against' the airflow making things somewhat harder. Chevy appears to have spring-loaded the door towards the Cool position to help with this but if the actuator is 'weak' and the blower is on high it may not be enough.
I'll replace the Temperature Actuator and let you know where things go from there but I think I've found the problem...
Barry
Well it looks like it may be the Temperature Actuator (the motor that changes the position of the door) and NOT the Temperature Valve/Blend Door itself!
After removing the Ash Tray and Glove Compartment for access (visual and tool) and observing the operation it became apparent that with the blower on high the actuator did not have enough 'umph' to move the door from the Heat to Cool position. It works fine moving from Cool to Heat and, with the blower off, it worked fine in BOTH directions. The test I did in my initial post was with the blower off so I could 'hear' the motor & door move and the lack of airflow is what gave me proper results.
Looks like when the door moves from Cool to Heat it is doing so 'with' the airflow through the HVAC which assists the motor greatly in moving the door. Moving from Heat to Cool goes 'against' the airflow making things somewhat harder. Chevy appears to have spring-loaded the door towards the Cool position to help with this but if the actuator is 'weak' and the blower is on high it may not be enough.
I'll replace the Temperature Actuator and let you know where things go from there but I think I've found the problem...
Barry
Hello!
I know this thread is a few years old, but I am hoping you can help me. I believe I also have a bad temp blend door actuator on my 1998 k1500. I was looking at it today and could not figure out for the life of me how to get it out. Any tips? Looks like it will be a bit easier to remove it if I can get the ash tray assembly out. My problem is I can't figure out how to get the ash tray assembly out. I do not see any screws or anything, and I am afraid to pry on it too much. Any advice is greatly appreciated!
August 17th, 2019, 11:12 AM
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Thanks Barry for a nice informative post. I have a 93 Silverado and do work for my sister on her 95 Yukon, so this information is invaluable. Especially since we know the air works on the Yukon, but it is blowing hot air and cold intermittently when on cool.
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