Street Rat

The ac/heater control does not change the air flow from the floor to vent, ac, defrost, and heater. The air blows out at the floor no matter what position the control lever is in. Could this little part be the source of my problem or am I looking for something else that may have broken?


http://www.parts123.com/parts123/yb....5Z50000050G~~~

DUB

YES ...this part can be part of your problem...but MAKE SURE that when you disconnect the vacuum harness from it...that you crank the engine and MAKE SURE that you have vacuum at the solid black hose in the vacuum harness connector. NO VACUUM...it will not work. Ad then you have a problem out in the engine compartment where the small hose that goes to the switch you plan on buying is not getting vacuum from the intake via the special 'T' fitting.

Make sure that the check valve at the intake vacuum hose ( silver one with one port on one side and two ports of different sizes on the other is ACTUALLY a check valve and will only allow vacuum to flow one way.

http://www.corvettemods.com/product....700aAiG38P8HAQ

Also the white filter in line with this check valve more than likely need to be replaced due to the filter material is gone and you can look through it.

DUB

Street Rat

Thanks DUB. I'll do some checking on those items and report back.

McVette

Ok I got a question to ask here....I am having same problem but man it is tight under that dash.....how hard is it to remove the dash?

Easy Mike

You can work with the 78-82 HVAC controls without removing the dash.

maxmachz

Guys, the MOST COMMON PROBLEM that results in this is the tiny little vacuum line came apart right behind the distributor. The vent position will stay floor only if there is no vacuum to the control.

If you worked in the distributor area on plug wires, cap, rotor, it is STUPID easy to have this little line come unhooked. Cheap and easy to go look!

samdjr74

You don't need to remove the dash, jut remove the glove box insert and you'll be able to get to the vent door control and the end of the cable.

Street Rat

I checked under the hood for the easy fixes. Everything looks good. So I guess it's time to dig into the console.

DUB

The vacuum control switch for your AC/heater can be accessed by removing the passenger side console strip. Then if it is still factory...it takes a Phillips head screw driver tip to remove the 2 screws. That's it.

That is another vacuum switch for the hot water shut off valve...NOT the same as the one in the initial post.

DO you have vacuum on the black hose that is made into the connector that goes to the switch you plan on replacing???

DUB

Street Rat

I haven't got that far yet DUB. Maybe today I can get a chance to diagnose it further.

DUB

DUB

Street Rat

I got to the vacuum selector switch and pulled the vacuum harness off. I was NOT getting vacuum to the selector via the black hose. So back under the hood to investigate.

What I found was a cracked vacuum line located right as it goes into the firewall behind the distributor. It was covered with ribbon strip caulk right where it was broken so I didn't see it the first time.

I got a short piece of vacuum hose and connected the two hoses together. Checked the vacuum harness for vacuum at the black hose. I had vacuum at the hose and all functions worked as they should.

THANKS GO TO DUB! He nailed it.

Now on to the next issue...

DUB

BOY..are you LUCKY!!! Glad that it is up and running correctly.

JUST a TIP for others. I run into Corvettes where this a hose that comes out of the firewall grommet breaks/splits right at the grommet. When this happens...I drill out the old hose in the grommet CAREFULLY and do my repair on the inside of the car using brass fittings and NOT plastic fittings. Because I only want to get into the dash ONE TIME. AND that is if the owner is concerned about the hose looking original (rubber). IF NOT...I use the hard plastic tubing that the newer Corvettes uses and I have the unions that can make everything work. And if in time the hard plastic line were to break...I can pull it out and easily slide one through the grommet.

DUB

melphis

Thank you. You nailed it.