SpeedyC2

My AC system was recently fully charged and holding pressure, but I was getting no cold air from the vents. Symptoms included the compressor not coming on when the AC switch was pressed, and the airflow from the vents noticeably dropping at the same time.

Trouble shooting this is out of my experience, so I took the car in for a look. The good news is dye was put in the system at the time of recharge and there are no signs of a leak at the compressor, dryer, evaporator, freeze sensor, etc. The tech did discover, however, there was no vacuum getting to the recirculation flap actuator, which meant the flap was not moving so cold air was not getting to the vents. He did not have time do to a full search for the vacuum leak at the time, but was able to come up with a temporary fix I hope will hold for a week or so until we can get back to it. He found a way to supply vacuum straight from the manifold, which allows the flap to function as intended and the AC to blow cold air - as long as I am not accelerating hard and losing vacuum! The AC is blowing cold for now, so there is a positive. I have noticed, however, there is a sound coming from the dash when I do accelerate which almost sounds like a turbo spooling up. My guess is maybe the vacuum actuator has a small leak? Does this sound like a (pending) failure of the actuator? Or maybe the line from the manifold is actually pulling too strong a vacuum so the system is leaking?

Either way, I hope all the vacuum lines can be thoroughly checked soon, and any bad lines, fittings, and/or actuators replaced. It's going to be a tedious job, I am afraid, but the lines are 26 years old now...

pp000830

First of all the vacuum-actuated flap behind the CCU is for air recirculation only. I believe even if it is closed the AC should be supplied air from the fresh air vent and so some level of cooling should be taking place

If the left or right mixing servo has failed and stays partially open it will add warmed air and reduce the effectiveness of the AC. Also if the fresh air servo is not opening, inoperative, I would think it would cause the fans to look for other sources of airflow such as heated air to draw upon.

You can easily check the recirculation actuator for leaks by attaching a small length of fuel or air hose to it and draw a static vacuum on it with your mouth if it is leaking it won't hold the position as actuated as you draw and hold vacuum.

Finally, the good news is the entire HVAC system has extensive fault code reporting so by running the codes on an OBD Code reader that can see the HVAC module you will likely zero in on the root cause of your problem.

Here is one of Tore's pages that discuss the HVAC system and its components' functions in detail.
https://993servicerepair.blogspot.co...sdom-page.html

Also if any of the servos prove to be bad one can buy replacements or for most of them save a lot of money by buying rebuild kits.
Here is a page discussing this among other HVAC issues:
https://993servicerepair.blogspot.co...?q=servomotors

Hope this helps,
Andy

SpeedyC2

As a follow up, a fully charged AC system combined with a thorough sorting/replacement of all vacuum lines and fittings (front and rear) and the confirmation all servos are functioning properly (I replaced non-functional defrost and foot well servos a while back) has the AC system fully up and running.

As we head into the dog-days of summer here in NC, it's great to finally have the system working as intended. It's not the most powerful AC I have ever experienced, but it has shown the ability to keep the cabin comfortable on several sunny days in the low 90's.

Now on to the next maintenance item, whatever it may be...