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I did the Heater Duo Valve Flush per the attached document. Solved the problem on my 2007 Coupe. I figure if it pops up again, I'll take the Duo Valve apart & replace parts per the Service Kit.
I updated the top post explaining the air routing through the ducts. The air is heated up first and then cooled. So when the valves let the water flow to the heater core, it will overload the AC core. At that point it's basically working as a defroster (hot air with moisture removal).
I did the Heater Duo Valve Flush per the attached document. Solved the problem on my 2007 Coupe. I figure if it pops up again, I'll take the Duo Valve apart & replace parts per the Service Kit.
I will try this as well.It might solve my warm air problem. I'm still going to have to figure out my fan speed controller.
I'm thinking that's a bad potentiometer.
Thanks,
John
I updated the top post explaining the air routing through the ducts. The air is heated up first and then cooled. So when the valves let the water flow to the heater core, it will overload the AC core. At that point it's basically working as a defroster (hot air with moisture removal).
I will try this as well.It might solve my warm air problem. I'm still going to have to figure out my fan speed controller.
I'm thinking that's a bad potentiometer.
Thanks,
John
When I had the sporadic fan issue on my 2007 Coupe, I took the HVAC Control Module out of the Vertical Console, separated the 2 control boards, filed a small notch in the HVAC Control Module plastic surround so the horizontal board would fully seat into the pin connection, applied a small of epoxy glue to keep the boards together, & then re-assembled everything (see CL770's attached procedure). I also took the time to spray some electronic cleaner on the pots on the backside of the HVAC Control Module. After I got everything together, I still had an HVAC fan speed problem. Only after I installed a new blower motor resistor did the HVAC fan speed problem go away. And the system is still working today per design specs. Did I fix multiple issues during all of this? Yeah, I did!
1) The Control Boards seating was fixed permanently.
2) Using Electronic Cleaner on the pots was a temporary solution & may surface again later on.
3) Replacing the Blower Motor Resistor will last until it fails down the road - it is a wearable item.
4) And while the procedure to kinda 'flush' the HVAC Duo Valve of any residue accumulated from the cooling system cleared up the lack of cool air during A/C Mode on the DS of the Dash, I'll re-build the Duo Valve sometime in the future. Easy task to do. (Note: So is the need to re-build the HVAC Duo Valve a clear indicator that the Cooling System needs to be Drained, Flushed, New Thermostat installed & Re-Filled with new Coolant? Probably!)
Last edited by dedwards0323; Nov 27, 2024 at 08:10 AM.
When I had the sporadic fan issue on my 2007 Coupe, I took the HVAC Control Module out of the Vertical Console, separated the 2 control boards, filed a small notch in the HVAC Control Module plastic surround so the horizontal board would fully seat into the pin connection, applied a small of epoxy glue to keep the boards together, & then re-assembled everything (see CL770's attached procedure). I also took the time to spray some electronic cleaner on the pots on the backside of the HVAC Control Module. After I got everything together, I still had an HVAC fan speed problem. Only after I installed a new blower motor resistor did the HVAC fan speed problem go away. And the system is still working today per design specs. Did I fix multiple issues during all of this? Yeah, I did!
1) The Control Boards seating was fixed permanently.
2) Using Electronic Cleaner on the pots was a temporary solution & may surface again later on.
3) Replacing the Blower Motor Resistor will last until it fails down the road - it is a wearable item.
4) And while the procedure to kinda 'flush' the HVAC Duo Valve of any residue accumulated from the cooling system cleared up the lack of cool air during A/C Mode on the DS of the Dash, I'll re-build the Duo Valve sometime in the future. Easy task to do. (Note: So is the need to re-build the HVAC Duo Valve a clear indicator that the Cooling System needs to be Drained, Flushed, New Thermostat installed & Re-Filled with new Coolant? Probably!)
I'll be taking the car off the road soon and I'll check into all of this. I plan on flushing the radiator soon, before it gets too cold. That has to be the original coolant in there.
Thank you for your help and advice.
Re: Hot Air when cool selected, AC
