B65062

Hi - hoping someone else has encountered this one and knows the likely fix, or where to look, on an '81. Yesterday, all A/C and vent controls were working perfectly. Got in this morning and noticed no air coming through the A/C (dash) vents, but cold air is coming out the defrost vent on top of the dash, for the windshield. Now, no matter what I select, A/C, vent, heat, etc...the air always comes through the defrost duct only. Temperature control is working fine. Any help?

I know there are vacuum controls involved, but not where to look or what to look for?! May be completely unrelated, but it happens the car also stalled on me a couple times while idling, when cold. Once on the road for 10-15 minutes or so, no worries, idles fine. It's a 4-speed car. when it stalled, I just started it right back up, no problem, and just needed to keep the revs up a bit before the light changes to green and away we go. While moving, no drivability issues at all, and again, once warm, no stalling. Related or not, any suggestions here also greatly appreciated!

Thanks,
Perry

SIXFOOTER

Could be a vac leak. The vac line that runs all the ac stuff is a small hard black plastic line with a white stripe that goes through a gromet on the firewall about in the middle. Start checking there and follow the vac lines.

marshal135

Definitely a vac leak.
Isolate the engine by disconnecting the vac line from the ac system.
If car idles and runs fine you have found your demon.
Now its just a matter of replacing the vac line.
Dr. Rebuild offers kits just for this. The right size hoses etc...
If it is like my 68 it comes through the firewall and goes to a pie plate
shaped actuator under the dash. If the corvette gods are kind you may see it with the passenger side lower dash pad removed. Get a strong flash light it is going to be your best friend under the dash of a corvette. Oh and yes you will bang you head allot
Marshal

C3 Vette Dude

Vacuum leak! Look at the wilcox diagrahm for leads on the vacuum lines. I would start at the rubber bulkhead grommet that is located under the hood in the fire wall. There should be three lines coming out. Follow them to the source. If not there, check underneath the A/C controls to see if any of the lines disconnected.

B65062

Thanks, Guys! The three lines coming through the firewall grommet are solid. BUT, while looking around I did find another coupe issues, possible contributors. There's a vacuum line that goes to a metal line that bends around the rear passenger side exhaust manifold which goes to the heat riser valve. It was competely pulled out of the actuator. Fixed that. I've needed to replace valve cover gaskets and a lot of vaccum lines have to come loose or out in order to get them out, so decided to dig in, and yep, found another, larger, vaccum line on the passenger side that has come loose. Now, I need help figuring out where it goes! Trying to attach a couple pics here. The far right rear intake manifold bold also secures a bracket that hold a device with both vaccum and electrical connections. No idea what this is - can someone tell me? The vacuum line leaves this device and continues forward running along the top of the valve cover and ends somewhere near the front, right, top of the motor...under the air pump. For some reason it has a straight fitting on the end, then another inch or so of rubber line. It has a purple stripe along one side visible only near the end. I'm really hoping this is related to my orginal problem! In any case, any help understanding where this belongs will help a lot. I've looked and looked and just can't see any open connections.

In about the same area, but above is also a loose electrical connector. Has a blue wire existing the main harness ending at the front right corner, and a green slide-on connector. Again, I know it can only go where it can reach, but I am failing to find it's home. Possible that it's for an option I don't have?

Thanks again folks - Perry

First two pics showing the vacuum line, next two the wire/connector

B65062

found the open port on the right front corner of the carb - that must be for the purple striped line, going to what must be the EGR solenoid. I'm going with it! Still wondering about that electrical connector...any help from '81 owners?

Now of course another question....the accordian type hose on top of the air pump just ends to open air. Doesn't look like it had been connected to anything....supposed to be that way, or am I missing something? See picture - thanks again!