Thursday, June 9, 2011

1999 Cadillac DeVille vents not opening?

Sounds like a vacuum problem. Do you have vacuum at the supply line (passenger side firewall)? If so, then it is under the dash somewhere. If not, then it is under the hood.

The parking brake is on the HVAC vacuum circuit. Start by checking the vacuum diaphram on the parking brake to see if it will hold vacuum.

The parking brake diaphram is at the end of the HVAC vacuum circuit. Start at the source like stoneage said at the vacuum reservoir under the battery tray, the check valve and vacuum lines all the way to the fire wall. If you have and hold vacuum there, then look under the dash at all the lines. The parking brake disphram is mounted on the parking brake assembly. You'll have to drop the hush panel under the dash but it will become readily apparent as it will have a vacuum hose to it.

The A/C system supplys the park brake with vaccum if the park brake doesnt relese then you dont have vaccum in the A/C system ....

There is a vaccum line thats goes to a can thats mounted under that battery tray , you have to lay on the ground under that corner of the car to find the can , once you find it, find the vaccum line that goes to it and follow it up all the way to the firewall .


go to l/f fender area and locate the vacume canister check for may have to replace it.Also check the criuse control for proper operation .if you have low vacume it wont operate. properly.check all vacume sys. for leaks. the emegency brake releace also. check the vacume
at a/c progamer.

Does the system change modes, and try to blow out vents. If it only blows out of one mode(defog/floor), there may be an actuator issue at fault. There is no 'vacume' in this system, the park brake release and cruise are electro-mechanical as well.
ok so that canister would be on a receiving end of the vacuum source. Which would make the source of the vacuum.
it is on the receiving end of the EVAP system, BUT it has to have a vacuum source as well. The vacuum source is at the manifold or TB.
What is that diaphram thing that has a throttle cable connected to it, then on the other side it has a large and a small vacuum hose comeing off. I can squeeze it and it pulls the throttle cable. I kind of figured that was the vacuum source. I had no vacuum on the large hose and the smaller one
cruise control servo.
Is it a vacuum source?
It is a vacuum recipient. Vacuum source is the engine intake manifold. ALL vacuum comes from the manifold (or is some cases the TB (behind the throttle plate).


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