Tntocco

So my A/c works wonderfully. All buttons on the climate control seem to function properly. But when I switch to heat there’s no hot air. Is this a flapper/mixer door problem???

belairbrian

Could be. Is this a C68 control (automatic HVAC)? If so you can put it in diagnostic mode and see what the mixer door status is.

Tntocco

I believe it is. How do I put it in diagnostic mode?

Tntocco

Also after some research I’m a bit confused which parameter I’m looking for

belairbrian

We might need to back up. I forgot to ask what year corvette. Early cars have heater valves. Which can stop hot water from circulating through the core. Later ones always circulate water.

But if you ran diagnostics like in this video, Did you have a flashing light and did you get a code 01 or 02?

Tntocco

my my car is a 1993. I will give all of this a try this weekend. Thanks a ton for all the help.

belairbrian

Since it's a 93 it definitely is a constant flow heater core.


Not sure when you bought the car, If new to you someone may have bypassed the heater core. Really hard to see since the fittings are under the coolant tank.


The motor is not fun to change. So if anything else could cause it, it's worth considering.

grandspt

Probably the blend door motor went bad. There is a plastic gear in the blend door motor assembly that cracks on the metal shaft that opens and closes the blend door.
The "auto" fan button usually becomes disabled (fan stops blowing when pressed) when it goes bad, at least mine did.

Tntocco

I did the diagnostic and got an 01 code

belairbrian

So the fault is somewhere in the blend door circuit.
Door motor, connector C295, or the Heat and A/c Programmer

First step is to disconnect negative battery for 1 minute to reset the system and see if it clears the problem.

The code 01 diagnostic chart starts on page 1C1-8 of the FSM.

kael

FYI for later readers, an '87 has constant flow core.