Carpokes Porsche Forum

Is it normal for the ac to cut out on any form of acceleration at all? I just performed an r134a conversion and even if I give it the slightest bit of throttle the ac goes out completely.

Doesn't sound normal. Mine does not do that. Is the compressor kicking off, or is the air just no longer cold? Might be vacuum related -- when you accelerate, you reduce engine vacuum -- maybe check the vacuum reservoir tank, and the lines and check valve going to the heater valve, brake booster, and firewall?

The air cuts out entirely, not just no longer cold. I do also have a broken vacuum line going to the valve to the right of the accelerator pedal in the footwell and was wondering if that is part of the problem. I know it controls a flapper door for the ac but I don’t know what its exact use is.

Is the blower cutting out, or is it still going with just no air coming out the vents? Have you checked to see if the air is coming out the footwell or defrost vents?

Poorsche44 wrote: Sun Aug 03, 2025 10:02 am I do also have a broken vacuum line going to the valve to the right of the accelerator pedal in the footwell and was wondering if that is part of the problem. I know it controls a flapper door for the ac but I don’t know what its exact use is.

I assume this is your '83, and yes, that is the problem. The vacuum in that line controls the flapper which switches the airflow from the heater system to the air conditioning system. There must be enough vacuum at idle to overcome the leakage, but as soon as vacuum drops, the flapper switches over.

By the way, Tom, good call on that. I'd never really thought about how the flapper was hooked up.

I went out and looked at my car to check the routing of the vacuum line. Other places to look for leakage would be the check valve at the brake booster, the Tee fitting behind the wiring just left (as you are looking at it) of center below the fresh air intake, and the connection at the vacuum booster.

Do you think the vacuum could still overpower the leakage at consistent throttle as well? The ac still blows under constant rpm and on deceleration, just cutting out on acceleration. I’ll order another one right now as the connection is broken off from the valve itself. Looking at it I’m not 100% sure how it’s connected to the car itself but I’m sure I’ll figure it out.

Just for fun i decided to zip tie that valve closed to see if it would be a quick impromptu fix and noticed no difference. I also should’ve mentioned earlier that the line is completely broken off from the valve, so the flapper was never actuating beforehand between idle and throttle

Poorsche44 wrote: Sun Aug 03, 2025 10:57 am Do you think the vacuum could still overpower the leakage at consistent throttle as well? The ac still blows under constant rpm and on deceleration, just cutting out on acceleration. I’ll order another one right now as the connection is broken off from the valve itself. Looking at it I’m not 100% sure how it’s connected to the car itself but I’m sure I’ll figure it out.

Yes, vacuum is generally at its lowest under acceleration vs. steady cruising (assuming you're not cruising at 150mph).

Based on new information, it would seem that your fans are turning off when you are accelerating. I think a passenger with their ear against the center vents would be able to hear the fan blades change pitch when spinning down and back up. This would indicate a loose connection somewhere, which I would assume will be a major pita to track down.