Join Date: Jun 2004
Location: In the Back of your Mind
The picture below shows how the vacuum lines are situated. All the little vacuum system 'elbows' are shown. This is in the elusive Section PD of the service manual...do you have that section? GRIN
Since your vacuum-actuated air intake flap (under the bonnet) doesn't open, I suspect that you have a vacuum issue. Did you pull the carpeted cover off the RH quarter window area and check the vacuum line connections?
Also... since you have a '93 we need to ask, does your car have power steering (indicating it is a 93.5)? If it doesn't, it has a vacuum pump at the LF side of the engine. The rubber fittings right near the crankshaft can crack when doing other work, reducing the vacuum available. (If you want to test with a gauge, you are looking for 18hg minimum up above the RH gas tank.)
If you DO have power steering,, your HVAC vacuum is provided by an electric pump in the compartment on the rear engine wall. An S4s owner I visited today found that his EBPV line was leaking (yes he had wired the valve open) so his pump would run 'forever'. Putting a cap on the control solenoid source (right-most on the engine side) allowed the electric pump to maintain vacuum by only running every few minutes.
One other thing to look for when you inspect the controls behind the radio: The actuator shafts that switch the vacuum on and off are supposed to have little plastic caps on their ends, that ride on the control cams. If those have fallen off, the modes won't work.
Post back when you get a chance to investigate....
Succasunna, NJ USA
"Not all angels have wings." - Turbo R