Thanks Roy, I really appreciate the help. I bought the compressor from Applied, so they'll most likely
provide a replacement. Finally found the old expansion valve this morning,
so when I get back might try putting it back in first. I only took it out because "your supposed to".
While it's not too likely I got two defective brand new expansion valves in a row, it is possible.
Too bad I'm out of refrigerant or I'd try it now.

I think I'll also switch to real Duracool though it's more expensive. I'm suspicious of the murky green color in the oil,
but can't figure out what it could be other than dye. While my understanding that Enviro-Safe is equivalent, I suspect they've
changed their formula (I ordered Glacier Gold originally, but Enviro-Safe is what they sent for whatever reason).

thanks again,

Karen
1975 26'

Low pressures and little cooling. Has to be lack of pumping, lack of charge or lack of restriction at expansion valve . Dumb question as new compressor---is rotation direction correct? And clutch is staying engaged?

Karen,

Take a look at AC info in this site. Your problem is mentioned there.

http://www.meicorporation.com/pdfs/Comp09.pdf


Some simple things can be so frustrating.

where?? I went through the whole document and didn't find it. The only troubleshooting is for blissfield/tecumseh/york
compressors and just says "low discharge and suction pressures": check for low refrigerant charge (already did that) and
leak check compressor. I don't see any leaks at the compressor and it's brand new.

Was there something else you found??

Karen
1975 26'


Adrien G. wrote on Mon, 30 March 2015 20:25

Karen,

Take a look at AC info in this site. Your problem is mentioned there.

http://www.meicorporation.com/pdfs/Comp09.pdf


Some simple things can be so frustrating.

Karen, The first page #211, scroll down to page #212 (trouble shooting chart) at "improper cooling" section. High suction pressure & low discharge pressure.

'new aluminum compressor'. Is this a Sanden? Isn't that a lower tonnage unit than an A6?

If I remember my GM history correctly cycling clutch started in 77. So your comp should stay engaged unless low or high pressure switches open as protection. So far so good. Lack of differential pressure points to the valve. They changed types and name for expansion valve or POA over the years. Obviously adding refigerant will raise the pressures low and high side. How does the low side site glass look as you charge it? Can you see vapor rushing past it? If so I would guess comp is ok. I think Emery said the glass is not accurate as a charge guide with HC12. If it goes clear liquid it is overcharged, unlike w R12. Sounds like you never reach a good point as you added and monitored charge so charge amount would have been good and cold at some point. I would refer to the FSM for your year to understand and diagnose your year's valve system. I think there is a bleed tube and temp sensing to control the throttling of the valve. In other words it's an active valving component, unlike the fixed orifice size and temp control done by cycling the comp on the later years. I'm guessing there is not enough pressure building across the valve. You should hear an RPM drop as you cycle from vent to AC, if only slight then the pump isn't using any horsepower to do work against the restriction. Do Jim Ks techs have any insights using this comp on your year with HC12?

If I remember my GM history correctly cycling clutch started in 77. So your comp should stay engaged unless low or high pressure switches open as protection. So far so good. Lack of differential pressure points to the valve. They changed types and name for expansion valve or POA over the years. Obviously adding refigerant will raise the pressures low and high side. How does the low side site glass look as you charge it? Can you see vapor rushing past it? If so I would guess comp is ok. I think Emery said the glass is not accurate as a charge guide with HC12. If it goes clear liquid it is overcharged, unlike w R12. Sounds like you never reach a good point as you added and monitored charge so charge amount would have been good and cold at some point. I would refer to the FSM for your year to understand and diagnose your year's valve system. I think there is a bleed tube and temp sensing to control the throttling of the valve. In other words it's an active valving component, unlike the fixed orifice size and temp control done by cycling the comp on the later years. I'm guessing there is not enough pressure building across the valve. You should hear an RPM drop as you cycle from vent to AC, if only slight then the pump isn't using any horsepower to do work against the restriction. Do Jim Ks techs have any insights using this comp on your year with HC12?

Bob, I have a 76 Grand Lemans and that has the non cyclling A6 I had a 77 Monte Carlo and that had the 'new' cycling A6 system. The cycling system would then coincide with the final HVAC desigb in the MH for 77. I remember owners manual explanation to make people aware of the cycling feel and state that it was normal. I could be wrong on the MH if they introduced the cycling clutch pre 77.