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RX-7 2nd Gen Specific (1986-92) RX-7 1986-92 Discussion including performance modifications and technical support sections.

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Old 03-31-2022, 08:18 AM   #1
RoughRex
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Default A/C trouble

I have been trying to diagnose this by myself but I'm about to give up and pay someone who knows what they are doing... assuming I can find someone who isn't going to try to make me convert to R134a. My AC has never worked very well but I recently removed my very brittle dash and decided to tackle this problem child while I have access. I removed all three HVAC boxes, cleaned the ridiculous amount of debris out and rebuilt all the flap seals out of closed cell foam.

I just replaced the dryer and the compressor (the compressor has been working but has been leaking from the shaft seal for a long time) and I have been having to top off annually. I drained and bench flushed the reman compressor with ester oil, they shipped it with PAG in it. I pulled a vacuum on the system and it holds fine for days but I attempted to charge it today with Freeze-12 and at no point during the charging was I able to get it to give me cold vent temps the best I could manage was around 55 which is about ambient right now, most of the time at idle (about 1k RPM) it sat at 60+-2 with two fans in front of the car blowing on the condenser. The system took a long time to empty a 12 oz can of refrigerant... I guess I don't know how long it's supposed to take but it seemed like way too long.

It seems like low side pressure is too high and it's not building enough high side pressure, it stayed low throughout charging unless I increased RPM (this is where I got my best reading of about 55 degrees somewhere mid charge). I'm currently getting about 50PSI low and 135 high at Idle or 39PSI low and 195PSI high at 2500 rpm neither of which makes the AC blow cold somehow.

Anyone have any AC insights? Is this reman four seasons compressor I got crap or have I missed something else? I don't understand how I got a 156PSI pressure differential at 2500 rpm but didn't get cold air.

*Edit: Ha! It turns out of course that I'm an idiot. Testing in a garage with limited airflow over the car and without recirc on... sucking all that hot engine air right into the blower. retested today and getting vent temps around 40, seems like the compressor shuts off if it tries to dip any lower... I assume that's the thermometer in the evap trying to prevent icing, it's not building any major pressure on the hot side... once it levels off it sits at about 28 low side and 125 high side which seems low but the air is cold and the sight glass is bubble free within seconds of the compressor starting... I guess I'll have to wait for it to actually be hot outside to know how well it's really working.
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Last edited by RoughRex; 04-01-2022 at 12:53 AM..
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