The biggest clue is that you say the filter housing (receiver drier) gets cold. This means there is a restriction or blockage there. The high side of the system, which is everything from the compressor outlet to the expansion valve, should be hot to the touch. After the expansion valve at the inlet to the evaporator should be cold, and all lines going back to the compressor should also be cool or sweating. Any restriction, anywhere in the system will cause a problem. You already removed the EPR valve, so that eliminates that common problem area, and you have changed the expansion valve, so that should not be the problem. My guess is a problem in the condenser or the drier.
My system is a 1962 installed into my 1960 300-F.
A mechanic tried to convert to 134A without taking the EPR valve out of the compressor. It worked great but would freeze up the evaporator and stop working.
Sent everything to Classic Air for rebuild and conversion. Their temperature switch makes and breaks power to the compressor blue wire if there is a freeze up. This replaces the function of the EPR pressure valve to cycle the compressor.
The evaporator is open and was blown out with compressed air.
System was charged and was not cold.
Classic Air said it was a bad expansion valve. Replaced it and no difference.
They said to charge the system with 134A at 80% of normal pressure. So they went down to 2.5 from 3 lbs.
Problem is that the filter housing on the top of the condenser gets cold but the line does not get cold where it enters the evaporator.
They put 4 lbs. in and I got 59 ° at the vents on the highway.
Pull off to the side of the road, with engine running, to see it working well and the cooling stops. Nothing frosting up.
Go back on the road and the cooling does not come back.
Waiting for another expansion valve and on/off switch to be delivered.
Will be replacing both once they come in.
Any insight about where we are now?
Thank you, in advance, for any help or suggestions.
Posted by: <dverity@xxxxxxxxxxx>
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