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Suddenly higher high-side pressures and short-cycling

58pacer on Sun September 07, 2008 7:37 PM User is offline

Year: 1993
Make: Mercury
Model: Sable
Engine Size: 3.8L
Refrigerant Type: R134a
Ambient Temp: 90
Pressure Low: 25-50
Pressure High: 250-315
Country of Origin: United States

Just replaced the toasted clutch with a new one, had the compressor off, I added an oz. or two of oil to the compressor, and evacuated.

A month or two ago, the system would stay on continuously with 30 oz. of refrigerant at low side pressures of 24-50 and high side 160 to 180, and outlet temperature of 43 degrees F. This was with a new compressor and the old clutch.

I must have damaged the clutch bearings swapping it onto the new compressor, because it seized in a month's time.

Now that I have replaced it and recharged, the outlet air temperature gets down to 40 degrees with only about 20 oz. of R134a. By the time I get to 24 oz. of charge, it is short-cycling a little and outlet air temp is up to 46 degrees.

Would a new, more "grabby" clutch cause this, or could it be because I added the small amount of oil?

TRB on Sun September 07, 2008 7:58 PM User is offlineView users profile

Did you check the orifice tube before putting it back together?

New clutch would not be the issue but too much oil could. Also a system full of debris or a condenser plugged could cause your issues.


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73Wagoneer on Sun September 07, 2008 8:13 PM User is offline

Edited: Sun September 07, 2008 at 8:14 PM by 73Wagoneer

58pacer on Mon September 08, 2008 12:34 PM User is offline

Old compressor was weak, but had not disintegrated when I pulled the system completely apart two months ago. O-tube had a small piece or two in it, and when flushing the other components, I got a few black chunks out, but overall the system was fairly clean inside.

This time, I had the new compressor open briefly, and it looked clean to the extent that I got into it, never thought it necessary to check the new orifice tube after only about a month of use...dumb, huh?

Given the O-tube, compressor, and accumulator drier were all replaced, and the evaporator and condenser were both flushed, and were pretty clean to start with, I think the system shouldn't be too gunky yet.

It's very possible I over-oiled it. Assuming that's the case, what would be the best course to take at this point? Leave it as is, reduce the charge to prevent the short cycling, or try to dump some of the oil?

Ideally, I'm sure it would be best to also check the O-tube, but if the system works well at 20 oz. of charge, would it be a bad idea to just continue to use it that way?

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