shadowman1

My a/c is blowing thru the defrost and floor vents only on my 93 w auto a/c. Found no vacuum leak. Will sometimes blow thru the dash for a short time then reverts to defrost and floor. Any common problems I should look for?

Thanks
Dave

flyingvette

You might look at the vacuum check valve which I believe is located under the passenger side fuel rail cover. I replaced mine a year ago for the same problem.

CoolRides

I had this happen on a 96 we had. It turned out to be the main vacuum connector on the AC programmer. The symptoms were very similar: First, it took for ever to switch the airflow to the dash vents. Later, there was no ability at all.

On some cars, there was a mismatch of materials between the two halves of the connector causing the vacuum paths through the "male" side of the connector to soften and collapse. This chokes off the vacuum to the actuators on the duct dampers.

One solution is to replace the programmer with one that has a male vacuum connector with open vacuum paths. This can cost $100 or more just for a used Programmer.

I ended up doing the tedious (but cheap) job of taking apart the programmer and inserting little copper tubes into each tube on the male connector. (Yes, I am probably a bit nuts. But hey, I love Corvettes.) Problem solved.

I was then amazed at how fast we got air to the dash vents. Obviously this problem had been coming on for a while...

Hope this helps!

BTW, we have another 96 that has been problem free in this regard. It was produced later in the year. Maybe they changed materials???

89 Bob L

Check the 3-way check valve at the rear of the engine, including the vacuum lines. Check the programmer connections. The programmer is located on the driver's side front floorboard just to the left of of the brake pedal. It is approx 3x5', black in color, and has two connections; electrical and vacuum harness. Check the vaccum harness connection to make sure it is secure (there is a bolt located in the middle of the harness). As to what you described, 95% of the time it is either the valve, a vacuum hose, or the programmer connection.

shadowman1

It was the check valve! Fixed! Thanks a bunch. Blowing just like it's supposed to.

shadowman1

Yes, it was the 3 way valve. Thanks.

Da Mail Man

......same thing happened to be...had part of the dash apart before i found out that there was a ck valve!......ugh!....glad it is fixed!

KBoltz

Mine started doing the same thing.

Where did you get your replacement?

89 Bob L

Nice to hear it was fixed.

shadowman1

Advance auto supply. $3.77 with tax. part # 47150 sku # 17190329