I have an old Singer refigeration unit 10ton, with
a coupland hermetic compressor, that is testing
me. It is a 1976 unit, but compressor was replaced
with a remanufactured unit in 1999.

This unit runs on freon 409a, and is a high temp
unit 38 degrees.

The problem I am having is low high side pressure
160psi, and very low low side 18" vacuum.

The unit has no leaks, and is properly charged.

I evacuated unit, and leak checked, all ok.
Filter dryers are ok also, and valves all
checked good. At these pressures, unit is only
producing about 20%. At this building there are
3 other Singer units 2 20 ton units, and another
10 ton unit. I have replaced compressors in 2
of the other 3 in the last 2 years, and no

The only item I have not checked is the expansion
valve, because it is 25' up on a ceiling in a large
cold vault surrounded by merchandise. But at
these preasures I do not feel valve is stuck.

Any ideas???