1998 pewter coup.on a recent stereo install, everything works great.except now my air direction selector does not work.air goes out in all ports.defrost,front dash and foot well.must of blown a fuse.the rest of controls work fine.every thing behind selector looks fine and connected but when you select a air direction noting happens.any ideas were this fuse might be?or what else might be wrong?thanks

 

I thought this was controlled by engine vacuum.

 

you are right, it is controlled by vacumme.so how to you check this? would it be easier to replace switch or take in and have a vacumme gage hooded up and checked to find leak.

 

PM sent, please answer.

 

you are right.now i got to figure out how to troubleshoot this vacumme problem.any ideas? thanks.

 

Two emails sent with trouble shooting and schematic information from Shop Manual. Good Luck !

 

thank for the email i appre the trouble shooting guide the hyperlinks off the chart do not work but its a start.cant wait to get started.thanks again for your help. lee corvt1

 

Your vacuum source originates from the back of the intake manifold off the cmall plastic nipple :



Then it goes down to the passengers fender well to the black plastic vacuum can:


The plastic vacuum line run inside the wiring harnesses under the battery.

If the battery has ever leaked acid, the acid will dissolve the vacuum lines in the harness!!

Bill

 

Bill's correct, probaly your battery leaked acid and destroyed your HVAC vacuum lines. To repair - jack up car, remove front right tire and remove the access panel (9/32" socket will be needed for several bolts in the fender well and underneath). Then from above, remove battery, remove battery tray (1/2" socket will do). Look for damage on metal surfaces from leaking battery acid. If you see any, you have leaking battery acid which probably got your HVAC vacuum lines. You'll have to nuetralize the battery acid using either baking soda and water (real messy) or you can use CRC's Battery Cleaner spray available at most auto parts stores. Trace your vacuum lines from the vacuum storage tank inside the right side fender. There's a check valve attached to the tank and two vacuum lines, one goes to your firewall grommet next to a silver cannister below the battery and the source line comes from the MAP sensor on the intake manifold as Bill has shown. Most likely, if acid did you in, the vacuum lines are rotted a few inches from the valve under the battery tray area. These lines are buried in the wiring harnesses that go through the battery compartment under the battery tray. More than likely, these lines are 'cooked' in the area under the battery from leaking acid. They are made up of 1/8" black nylon emissions tubing which you can get at any Auto Zone, Advanced Auto, etc. Mine were destroyed. I found the damaged lines and cut them back until I got undamaged line and spliced them using 1/8" line and 1/8" splices. I also replaced the damaged check valve. I did this to minimize the repair time, Otherwise you'll have to slide the intake manifold forward to get to the MAP sensor vacuum source and find the vacuum distribution block under the dash if you want to run all new lines. Note if this is what's wrong, get yourself an OPTIMA Red top or other Glass Mat type battery that won't leak. I made the mistake of doing the repair, replacing the battery with a regular battery, that leaked and detroyed the vacuum lines again. Repaired them again and bought the Optima. Good luck!