Automotive Air Conditioning Information Forum

I recently did a complete restoration of the AC system in my '89 Mazda RX7 turbo. Purchased a rebuilt compressor (Nippon Denso model), new receiver/dryer and new expansion valve. Old compressor finally seized up. Also replaced all O-rings & properly flushed out all the reused components (hard lines, condenser, evap core, hoses.). Since this was an R12 system, and R134 sucks in these cars unless you re-engineer & replace the condenser, I decided to charge the system with HFC152a (AKA computer duster gas) per a write-up on the RX7 forums, and the system is cooling rather well. The rebuilt compressor was "bench flushed" to remove any mineral oil in it, and was refilled with proper amount of Ester oil, per the Mazda FSM. The Ester oil is supposed to be compatible with the HFC152a and R134 refrigerants. The A/C system charged up perfectly and is cooling very well - air temps at the vents is about 40* F with 90*F ambient temps.

So on to my problem - I noticed recently that when I switch off the AC, the compressor is staying at least partially engaged. Problem is intermittent so far, and system has been in use for a couple of weeks since the restoration was done. Tested the AC electrical system, and verified that there is no power being applied to the compressor clutch when this occurs. When it does this, if I shut the engine down and try to rotate the compressor by hand in both directions, at first it will feel like I'm trying to crank over the engine (i.e., VERY hard to turn), then it "breaks loose", and I can rotate just the compressor, which feels normal - rotates freely with a normal amount of resistance to it.

I'm guessing I'll need to ship this compressor back to the seller under warranty, but before I do, is there anything I could do to perhaps just fix the clutch to get it to behave correctly? I'm thinking there may be some crud in the clutch causing this mechanical lock-up; maybe it could be flushed out somehow? Pulling the compressor is a major PITA that I'd like to avoid if possible.

Thanks!

Probably best to return the compressor to the rebuilder. Be sure to tell them which refrigerant you are using.

I've been in contact with the rebuilder, they said the issue is likely shipping/handling damage. Apparently these clutches have pretty tight tolerances, and it doesn't take much of an impact to cause a clutch to behave this way. Also told them that I'm using HFC152a for refrigerant, and was expecting them not to honor my warranty, but they are anyway

Unfortunately they don't have enough spare clutch assemblies so that I could just swap that in, rather than swapping in the whole compressor, which would have saved me the step of evacuating & charging up the system again. Good thing I'm using HFC152a though, at about $10 for 4x 10 oz cans at Walmart, I can't complain!