1970 Oldsmobile AC Woes

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tdhill01
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1970 Oldsmobile AC Woes

Postby tdhill01 » Sun Aug 16, 2020 6:37 am

I have a 1970 Olds 442 and as I went through the process of rehabbing her I bought all new/rebuilt AC parts - Parallel Flow Condenser, Drier, AC Box with Expansion Valve, POA Valve, Evaporator, and blower. I also has the POA valve set up for R134a, the A6 compressor was rebuilt and filled with 10.5 ounces of Ester Refrigerant oil, all new AC hoses - again everything was new or rebuilt. The inside AC/Heater box was also gone through - vacuum hoses, actuators and switches were all gone over and everything seems to work great.

My problem is after assembling the AC components in my car and getting a shop to fill it up with 3.2 pounds of R134a it would not blow anything out except for the ambient air temperature. The compressor seems to run fine, I am not hearing anything that would cause me to think there is a problem. The POA valve becomes very cold after the Low Side port and following through towards the compressor. The Expansion valve is warm, I hooked up gauges and got 90 psi at the Low Side port and 150 psi at the High Side port. I had the shop evacuate the system and place only 2.5 pounds of R134a but that produced the same results. I left the shop after I had them evacuate the system so I could take the system apart - this is where I stand at the moment.

Should I have flushed the AC parts before putting them on - I didn't think I needed to since all parts were new or rebuilt and everything was capped so no contaminates could enter. What did I miss? Looking for guidance here.
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bohica2xo
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Re: 1970 Oldsmobile AC Woes

Postby bohica2xo » Sun Aug 16, 2020 8:51 am

90 psi on the low side port sounds like a stuck (or badly misadjusted) POA valve.

Here is a video of testing the POA:

https://www.youtube.com/watch?time_continue=68&v=PhWW7hD9-Yw&feature=emb_logo
Dougflas
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Re: 1970 Oldsmobile AC Woes

Postby Dougflas » Sun Aug 16, 2020 10:03 am

Hook up the gauges and unplug the blower motor. The low side should drop to 26PSI. If not bad POA is most probable cause.
tdhill01
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Re: 1970 Oldsmobile AC Woes

Postby tdhill01 » Mon Aug 17, 2020 2:20 am

Thanks, I'll gives those ideas a try.
tdhill01
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Joined: Sun Aug 16, 2020 6:14 am

Re: 1970 Oldsmobile AC Woes

Postby tdhill01 » Thu Sep 24, 2020 7:19 pm

POA was defective - all good now after replacement!
Al9
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Re: 1970 Oldsmobile AC Woes

Postby Al9 » Fri Sep 25, 2020 1:09 am

Interesting point to note here, a POA that closes too much lowers the high side below normal values even with a fully charged system, almost as with a destroked variable compressor.
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JohnHere
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Re: 1970 Oldsmobile AC Woes

Postby JohnHere » Fri Sep 25, 2020 8:39 am

If I understand correctly, you had the shop recover the original 3.2-pound charge and then recharge the system with 2.5 pounds. I don't think you mentioned pulling a good vacuum on the system for at least a couple of hours. Was that done as well?

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