revets00

I searched and try to find some discussions on 89 Climate Control. Seems the older C4's were manual. I'm having a problem with the heat not shutting off when you turn on the ac. Years ago I installed a water cutoff off on the heater inlet hose under the hood. This helped put you don't have your defroster when you need it.
I'm thinking the heat valve for these has been discontinued. I was told to look in a junkyard by some of the Corvette parts places. The 89 has the climate control heat and ac. Has anyone had this problem? Is it an electrical problem in the climate control or a vacuum or bad valve? If so how to you get to it? Where do you get one?
Has anyone converted their old freon to R22? Mine still has the old stuff.
I wonder if it would be ok to change to R22 and change the inline filter?
Thanks: ack:

Patsgarage

I have not had any of the problems you describe with my (wifes) 89, but I can help with the A/C. First you want to change to R134-A, not R22. The system will have to be completely evacuated and all the seals (O rings) should be changed. The older ones do not like the newer Pag oil that 134 uses. You should also change the dryer/reciever while the system is open. Other than that is is pretty straightforward. The original compressor should work, but you will loose some cooling capacity compared to the original R-12 system.

Cliff Harris

The C68 automatic HVAC system was first available on the '86 Corvettes -- I was quite happy to find it on the option sheet and ordered it. The C60 manual system was available for many years. I don't know if went all the way to '96 or was discontinued earlier.

For reference, I'm still running R12 in my '86. I found no compelling reason to change. I've had it recharged one time. The AC guy wheeled out a R134 cart. I told him I had R12. He wheeled out a R12 cart. No big deal (except it costs more).

It sounds like your blend door is stuck in the HEAT position. This door's position is controlled by the blend door motor. The blend door motor is controlled by the HVAC programmer, which is right above the gas pedal. The HVAC programmer is controlled by the HVAC control panel.

You can check the operation of the blend door by removing the blower fan module from the evaporator housing. The blend door is visible through the hole. The HVAC controller cycles the blend door from full heat to full cold to calibrate the feedback potentiometer every time you turn on the ignition. Watch the blend door while somebody turns on the ignition and you should see the blend door calibrate. After it goes to both extremes it is set to the position determined by the temperature setting.

There are two 140 ohm resistors on the HVAC programmer PC board that reduce the voltage to the blend door motor. These resistors get VERY hot and over time the solder connections crystalize and stop making a good connection. Sometimes the resistors burn up. Here are some links to info on this:

http://forums.corvetteforum.com/c4-t...schematic.html
http://www.batee.com/corvette/acrepa...oard/index.htm

howardjm

My control all works with the exception of the temp. it will decrease on the display but will not increase when pushing the warm button. If I disconect the battery and reconnect the temp will be on 78, any suggestions?

65Z01

It does sound like a Blend Door issue.

There is a rod that connects the Blend Door to a shaft comming out of the Blend Door Mtr. The connection is made by a white plastic piece; on my prior '88 that piece broke, keeping the Blend Door in the Heat position.

If you drop the RH hush panel you can look up and see the rod and motor shaft mentioned above. Then cycle the Auto Temp control between min & max settings while watching the motor shaft & rod; both should move with the temp setting. If the motor shaft doesn't move the problem is in the HVAC control assy. I suspect the plastic connector is broken/missing, as is was with my issue.

red89c4

There are two 140 ohm resistors on the HVAC programmer PC board that reduce the voltage to the blend door motor. These resistors get VERY hot and over time the solder connections crystalize and stop making a good connection. Sometimes the resistors burn up. Here are some links to info on this:

http://forums.corvetteforum.com/c4-t...schematic.html
http://www.batee.com/corvette/acrepa...oard/index.htm[/QUOTE]


mine had the same symptoms as you described. followed the links above and resoldered the resistors in the programmer. Fixed! Cost, zero!!!

the programmer is located above the brake pedal, remove and repair.

Ray Quayle

Cliff, To be completely accurate your statement should read "The C68 automatic HVAC system was first available on the '86 Corvette Coupes." All '86 Convertibles had C60. For the '87 Model Year, C68 was available in both Coupes and Convertibles.