Air Con problem...need some expect help!
 

Months ago, my A/C acted funny, started to have a recycling hisssing sound and few weeks later the air was not getting cold anymore.

1) Took it in to a mechanic, he suspected it was the evaporator, put dye and recharged system, but could not find an obvious leak anywhere.
Upon my request, he re-checked the system with the Porsche Tester and found that the A/C ballast resistor was bad, replaced it and the air blew cold for 1 or 2 days.

2) Went to another mechanic, he had his Porsche Tester hooked up, but whenever he select the air con mode, it would actually turned off the A/C in the car! He said he has not seen this before as he needs to run the tests while the A/C is on.... He did some manual checking and there are some inconsistent behavier from the temp setting knob, thinks the CCU is in question! He is going to borrow a CCU so he can make sure before repair.

Here I am, crossing my fingers the 2nd mechanic is on the right track.

Hope one of you A/C expert, ToreB or Randall can have some helpful hint.

_____________
'97 Blk/Blk C2S

Hi there! My CCU shut down all fans when I connect the OBD tool, so I would think you're observing normal behaviour there.
To your hissing sound on resirc setting:
You are probably having a vacuum leak somewhere, most probably a disconnected vacuum hose. Either on the resirc flap actuator or at the valve i the trunk.
Pressing resirc closes the mix (heat) and fresh air valves. These are electric servo operated. Then the resirc flap should open to draw air from the cabin. If this fails to open the fans will draw air over closed vents and other small openings. This is causing the wheezing sound.
For vacuum issues, have a look here for details:
www.ccu.tore.bergvill.com
Cheers,
Tore

See this as well: http://p-car.com/diy/acdiag.html

And don't discount the fact that there might be more than one problem, mine ended up needing a recharge, having a disconnected vacuum line (and another "mystery" vacuum line in the same place, making the diagnosis that much harder), and missing hinge pin from the recirc flap actuator arm, meaning that even with good vacuum, the flap didn't close properly.

Find someone who will go over methodically, step-by-step.

Well mine was making a wheeezing sound last summer.

It turned out to be a split rubber elbow that attaches to one of the vacuum spigots on the connecting tube between the two intake manifolds.

Worth a look.