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Well, it's cold here in Nebraska, so for the most part, I will keep the Vette in the garage. Every once in a while, I will take it out because I don't want it sitting in the garage for 3 months. (yes I have the battery on a maintenance charge)
Recently, I did replace my A/C Climate Heat Control Module Switch because the buttons on mine were worn out, faded screen etc. So, it's about 40 degrees outside, turn both ***** to heater (red) and try to set the heat to 80 degreas, set it to blow
on the windshield (defrost) and on my feet. When I do this, the AC light comes on (????)
5 minutes late..... uh .. not much heat. 10 minutes later... maybe some heat??? but nothing significant. I mean if this was my Silverado, I would be sweating!!
1. Whats with the AC light coming on when you turn the heat on?
2. Does it jus take forever for these things to heat up, or do you think I have a thermostat problem?
As always you guys have been amazing for the help!!
Happy Holidays !
Todd
Hey Todd,
Nice to hear you exercise the Vette, I wish I could with mine but its locked in storage!
1. About your A/C, most cars will actually run you the A/C (wether they indicate it or not) when you send air to the windshield, since it defogs your windshield better. The Vette will put the light on because GM designed it to be on whenever the AC is on.
Now if it drops below ~3 deg Celsius (37 F) then the AC will turn off since it really cant dry the air anymore than it already will be. Pushing the "A/C" button will just have it blink at you saying "Not gonna happen pal!"
2. What were your coolant temps? Was the car warmed up somewhat to the point where you would expect heat? For me it usually needs to be about 60 degrees Celsius (140F) before the Vette will give much heat. If the engine was warmed up, I suspect you have an HVAC issue with with vacuum lines or the air is not being directed correctly.
I assume you have the Auto climate module since you said "screen" - please confirm.
When you crank it to full hot or full cold do you hear some sort of whirring or noise in the dash? You should be able to hear the flaps moving to direct air over the heatercore.
Thanks for getting back to me so soon! This is the module I was referring to
After 10 minutes, I think the car was up to "normal temperature" So I think I'm going to have to take a look at the HVAC. It's not a MAJOR issue. Not like I'm going
to put a lot of miles on the convertible LOL, just thought it was weird that it never really seemed to get warm in the car.
Ah... one thing to tinker with during the winter!!
Nice to have a heated garage !
Todd
When you crank it to full hot or full cold do you hear some sort of whirring or noise in the dash? You should be able to hear the flaps moving to direct air over the heatercore. Just saw this.... Not sure what THAT means??? I can hear the air blowing through the vents fine, not whirring or anything
Todd
Man I would love a heated garage!!
The HVAC is all just flaps controlling where air goes (Face, windshield, foot, over the heater core etc). If you can't hear the flaps moving you have a problem, either with the controller, your replacement (maybe connector not seated?) or the stepper motors are dying / dead.
To test:
Set your fan to low so its not making much noise, radio off, with the car in "on/run" but engine not running (so its as quiet as possible).
Passenger **** facing up (this sets it to sync with the drivers ****)
Turn the drivers **** all the way to cold, over the next second or so you should hear a noise of the flaps moving. Do the same but now to full hot, again you should hear some movement.
If you don't hear anything try changing where the air coming from by hitting "MODE", you should also hear some noises in the dash then.
I would expect you hear at least some flaps moving either for "MODE" or temperature. If none do, I'd suspect an issue in the HVAC controller or wiring - unlikely all the steppers die at the same time..
Report back!
Edit: One more thing, at least when I drive mine in the cold after 10 min its just getting to start blowing warm air. Its possible if it was quite cold the engine still wasn't warm enough!
Did what you said
The screen displays
Ext Temp 41
Set Temp 90
Fan on lowest setting
I have the mode set to air blowing on feet and main vents on face.
I can hear the fans blowing but that is it. When I set the car to the "on/run", the only sound I hear are the normal sounds which I believe is fuel pump pump priming
Todd
Just looked at a YouTube... Now I see what you are saying about the "Whirrling sounds" I should hear when I move those ***** !
I guess I need to do a diagnostic and check for HVAC codes ? Maybe I have a dash removal needed this winter?!!???
Man I would love a heated garage!!
The HVAC is all just flaps controlling where air goes (Face, windshield, foot, over the heater core etc). If you can't hear the flaps moving you have a problem, either with the controller, your replacement (maybe connector not seated?) or the stepper motors are dying / dead.
To test:
Set your fan to low so its not making much noise, radio off, with the car in "on/run" but engine not running (so its as quiet as possible).
Passenger **** facing up (this sets it to sync with the drivers ****)
Turn the drivers **** all the way to cold, over the next second or so you should hear a noise of the flaps moving. Do the same but now to full hot, again you should hear some movement.
If you don't hear anything try changing where the air coming from by hitting "MODE", you should also hear some noises in the dash then.
I would expect you hear at least some flaps moving either for "MODE" or temperature. If none do, I'd suspect an issue in the HVAC controller or wiring - unlikely all the steppers die at the same time..
Report back!
Edit: One more thing, at least when I drive mine in the cold after 10 min its just getting to start blowing warm air. Its possible if it was quite cold the engine still wasn't warm enough!
Let me tell you something about a heated garage. I have one. The mice love it, too. So I stopped heating it unless I'm out there!! Damn mice. My Mouseblocker has NO effect on them, either. Waste of $$$
Just looked at a YouTube... Now I see what you are saying about the "Whirrling sounds" I should hear when I move those ***** !
I guess I need to do a diagnostic and check for HVAC codes ? Maybe I have a dash removal needed this winter?!!???
Todd
Glad you found a video, I should have linked one.
You can check for HVAC codes in the dash (lookup getting codes from DIC C5 corvette) though I am not sure this failure will give you any.
Prior to installing your new HVAC controller did it work? Like I said may be a bad controller or connection.
If it is indeed bad steppers, I think its a semi-dash out job. Great for winter time just heat the garage so the plastics are not so brittle!
Re mice: Yea I can see them loving it - they are a real pest!!! They chewed the weather stripping off my garage door just to try and sneak a peak at my beautiful vette..
From my research the electronic sound emitting devices for mice are complete BS, I use traps now with PB and try to plug the holes (weather stripping) where they come in, I imagine with heat though they are quite determined!!
Let me tell you something about a heated garage. I have one. The mice love it, too. So I stopped heating it unless I'm out there!! Damn mice. My Mouseblocker has NO effect on them, either. Waste of $$$
Actually I do the same, I keep the garage at about 40 degrees. nothing freezes and keeps the mice out. When it's time to work on the car or bikes, I turn up the heat. So far, I have no problems with mice.
I'm not out in the country, so that helps and just enough hawks and stuff helps too!
What year car is this? The 2001-up models have the better blend door actuators that the early ones don't. Early ones don't have an internal positive mechanical stop. IIRC, you can pull fuse 27, and wait at least 5 minutes before reinstalling it. After the reinstall, the actuators will try to reset. On earlier, non stop units, they can push or pull the actuating rod too far, and then can't orient themselves to the proper position. Often, the plastic gear inside splits open, and then the shaft it was pressed on can't turn with the gear. If you need new blend door actuators, the really cheap ones out there for sale are almost always the older, less desirable design. The newer ones are usually much pricier, but they're really the only way to go, IF that's the problem. Hope this helps......
Last edited by grinder11; Dec 19, 2025 at 12:35 PM.
What year car is this? The 2001-up models have the better blend door actuators that the early ones don't. Early ones don't have an internal positive mechanical stop. IIRC, you can pull fuse 27, and wait at least 5 minutes before reinstalling it. After the reinstall, the actuators will try to reset. On earlier, non stop units, they can push or pull the actuating rod too far, and then can't orient themselves to the proper position. Often, the plastic gear inside splits open, and then the shaft it was pressed on can't turn with the gear. If you need new blend door actuators, the really cheap ones out there for sale are almost always the older, less desirable design. The newer ones are usually much pricier, but they're really the only way to go, IF that's the problem. Hope this helps......
You can check for HVAC codes in the dash (lookup getting codes from DIC C5 corvette) though I am not sure this failure will give you any.
Prior to installing your new HVAC controller did it work? Like I said may be a bad controller or connection.
If it is indeed bad steppers, I think its a semi-dash out job. Great for winter time just heat the garage so the plastics are not so brittle!
Re mice: Yea I can see them loving it - they are a real pest!!! They chewed the weather stripping off my garage door just to try and sneak a peak at my beautiful vette..
From my research the electronic sound emitting devices for mice are complete BS, I use traps now with PB and try to plug the holes (weather stripping) where they come in, I imagine with heat though they are quite determined!!
Cheers,
korak
Korak ,
Thought I would reply. First, to everyone thanks for all the help. The saga continues, but I am getting closer. Took the Vette out for a spin. Before I did a diagnostic, no HVAC codes.
Went for a drive got it up to running temp, coolant was at 176. Make a long story short, there is heat coming out of the passenger side but not out of the driver side. SO I am sure that is significant.
BTW no heat at all coming from the defrost
Glad you were able to do some "field" tests.
Great so we know you don't have any engine coolant issues, the heater core is flowing properly.
More than likely the control system to run air over the heater core for the driver is not working properly.
This is about where my expertise runs out on this topic so I'll leave it for others to comment on next steps.
If you haven't yet, Id follow the reset procedure grinder mentioned. If not some googling will find you the manuals for your car and you an start working through diagnosing there.
Report back if you get stuck! (Or if you solve it to help others in the future )
Corvette's in the Cold
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