Pirate102

My 93 does not select vents properly.. blows either defrost (most settings) or defrost and floor (heater/bilevel). Also the cruise will not engage. Any ideas? Probaly vacuum lines, but I am having trouble locating them.

sailorsteve

Your first move should be to buy a Factory Service Manual. Lots of troubleshooting help in it. C4's (and all contemporary cars) have many complicated systems that can't be serviced unless you have an idea how they work. Your cruise problem could be as simple as the defeat switch on the brake or clutch pedal being out of adjustment.

aminnich

Look for the fitting under the pass side fuel rail cover with two lines coming off it. One line goes to the HVAC and the other goes to the cruise control.

Redeasysport

It is a check valve and can be found in the "Help" section at most parts stores.

Pirate102

thank you

Pirate102

Just picked up a service manual

Ramrod92

In the Red Help section at Autozone Help/GM 1983-2008 Two-Way Vacuum Check ValvePart Number:
47150




Features & Benefits

Replace when worn or damaged
Part Number: 47150
Weight: 0.02 lbs
Description: Two-way check valve

STL94LT1

Pirate102

Picked up the 2 way valve from Autozone, mine crumbled to pieces when removing, but nothing changed...cruise still inop and thre hvac blows out of defrost only.

sailorsteve

Section 1B1 of your fsm has info on diagnosing the hvac.

aminnich

Any debris in the lines? I would check vacuum at the cruise servo next since it is so very easy to do.

Redeasysport

Check the hose going into the intake with your finger to ensure you have vacuum to the valve. You might have pugged it up.