[Rwinter]

I just did one of those autozone do it yourself AC charge things yesterday, initially the gauge showed 24 pounds (just under properly charged) as I added 134a into it, it stayed at 24lbs until the can was empty and finally showed 27-30 lbs. Today, I ran it with AC and could feel the engine drag intermittently (regular interval). With the AC off, no drag, so I'm pretty sure its an AC issue. Could the compressor be locking in safe mode due to an overcharge? And more importantly, how do I bleed some 134 out of it. Do I use high-side or low-side? and How do I release the needle valve to let it out?

Any help would be appreciated!

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[jlm968]

I know there's a low-pressure cutoff switch, but I don't think there's a high-pressure cutoff switch in the 944/968 system, which means your AC compressor clutch wouldn't be activated if you don't have a sufficient amount of refrigerant in the system.

And it's unlikely you'ver over-filled using a DIY can because your system couldn't take in more pressure than the can.

It sounds to me as if your system has not been run in a while, and perhaps you're simply not accustomed to the amount of drag the AC compressor creates when you activate it while the engine is running at idle speeds. It can create a parasitic loss as much as 30 hp.

Make sure to charge a bit of lubricant into the system.

Other than that, the important thing to note is whether or not significantly cooled air is coming through the interior vents.

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[rustech]

Yes, the AC system can act that way if it's overcharged. The lag interval you're feeling is in fact the compressor clutch engaging/disengaging due to the pressure peaking. I'm not sure what the best way to bleed off freon is at this point. If you do it from the low pressure fitting, it'll probably push the oil out first....so maybe from the high side with the car OFF would be the best choice. You just need to make sure that when you're done, you have the proper ratio of oil to freon. Good luck.

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[Rwinter]

Thanks for the input, Im not sure how to release the pressure on the high side, but I think your right about the oil coming out on the low side. Hmm, I was worried this wouldnt be easy.

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[gryphon]

<!--quoteo(post=71043:date=Apr 29 2009, 01:49 PM:name=Rwinter)-->QUOTE (Rwinter @ Apr 29 2009, 01:49 PM) <{POST_SNAPBACK}><!--quotec-->Thanks for the input, Im not sure how to release the pressure on the high side, but I think your right about the oil coming out on the low side. Hmm, I was worried this wouldnt be easy.<!--QuoteEnd--><!--QuoteEEnd-->

I haven't done this on a 968 but on another vehicle I simply used a small punch to depress the Schrader valve. Eye protection is wise.

Tom

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