rikkilee vette

I have a 1987 corvette with the digital dash. The auto button on the ac controller turns on the ac compressor and normally the ac air comes out of the front face vents. however now the air flow is also coming out of the defroster vent. This also happens with the econ button which is just the fan. It seems to be sharing about 50/50. Would anyone have an idea what could be causing this. The heater never has hot air coming out but has been blowing in the right direction. The main concern is the ac air flow as I'm in Phoenix (HOT). Any help would be much appreciated.
Thanks,
Rick

Cliff Harris

Prime symptom of a bad vacuum check valve. About $4 at any auto parts store. This is your guy:

rikkilee vette

I've located the check valve and will replace it. Sure can't complain about such a simple inexpensive fix. I'll let you know after I replace it.

Thanks Cliff,
Rick

rikkilee vette

Hi Cliff, I replaced the Vacuum Check Valve with an ac Delco part and the problem still exists with the AC air split 50/50 between the defrost vent and the face vents. I thought I would ask where the next place to look for the problem would be. I hope it is not behind the dash. Thanks for your time on this.
Rick

beerme

Same problem, same year and model. I always assumed it is a weak vacuum connection because I changed my cam and I know the plastic vacuum line which is in the main wire harness broke so I patched it with a rubber line, again figuring this was better than nothing.

So based upon my experience I would recommend you check for vacuum leaks or a cracked vacuum line with in the main wire harness, and under the passenger side dash where another check valve connection exist.

Best of luck...

Cliff Harris

That's just a connector to join the vacuum lines on the engine side to the vacuum lines in the cabin.

rikkilee vette

I will get back at a time to check over those vacuum lines.

Thanks again!

Cruisinfanatic

had same problem in mine a few years ago. Found mice had chewed a couple lines in back of controller right in half.