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low pressure

trackman on Thu November 08, 2007 11:36 PM User is offline

Year: 1979
Make: lincoln
Model: continental
Engine Size: 400ci
Refrigerant Type: r12
Ambient Temp: 60
Pressure Low: 34
Pressure High: 80
Country of Origin: United States

I installed all new parts, compressor,filter/dryer,expansion valve and a nos poa valve which I got off E-Bay.Flushed condenser,evaporator and all hoses using Safe-Flush. Blew everything out with shop air and nitrogen. Put 6oz. oil in compressor, 2 in filter and condenser and 3 in evaporator. Vacuumed system for one hour and recharged with 68 oz. using charging station. The air temp. that day was only 60 degrees and vent could only get down to 50 degrees at 1500 rpm or driving speed. Low reading 34 high 80. I put cardboard in front of condenser and high side came up to 90 psi. Why can't I get a higher head pressure and lower vent?

2POINTautO on Fri November 09, 2007 1:08 AM User is offlineView users profile

I do not know the specs for your car but I went hmmmmmmmmmmmm when I saw how much oil you put in, does your car really take that much. How hot is the compressor itself getting, be carefull touching it.

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Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

bohica2xo on Fri November 09, 2007 3:10 AM User is offline

Trackman:

Which low pressure port were you using? Many Lincolns of that vintage have an evaporator pressure port, as well as a compressor suction port.

The oil quantity looks right, hopefully you put the oil in the compressor sump. If you are sure of the refrigerant charge weight (my book shows 72 ounces), then the suspects are the TXV & the compressor. Is the TXV sensing bulb clamped to the evaporator discharge in the proper place, and well insulated from engine heat? What does the sightglass look like?


2.0: This is a real car, not a jap can. A6 compressor with sump, 70+ ounces of R12.


B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

trackman on Fri November 09, 2007 9:26 AM User is offline

2POINTautO: My shop manual calls for a total oil charge of 10 1/2 oz. The compressor is not getting hot at all, running very cool.

trackman on Fri November 09, 2007 9:42 AM User is offline

bohica2xo: There is only one suction port located directly on the POA valve. My shop manual says 68 oz. plus 4 oz. minus 0. I poured the oil into the suction port of the compressor while rotating clutch to draw it in. The sensing bulb is well clamped and insulated. There is no sightglass in the system.

2POINTautO on Fri November 09, 2007 10:10 AM User is offlineView users profile

AC Systems have a hard coded pressure / temperature differential chart, it appears that your compressor is not doing its job. It should be to hot to handle like my old girlfriend. Wait a minute, she was in fact being over handled.................by everyone...................

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

trackman on Fri November 09, 2007 10:40 AM User is offline

2pointautO: Thanks for that information. Before I go and buy another new compressor is there any way I can check it?

bohica2xo on Fri November 09, 2007 11:34 AM User is offline

Trackman:

The A6 has a sump, with a drain plug. It is always best to put oil in sump initally, since it is also equipped with an oil pump.

You can use Mitch's bench test for the A6 as well as the HR6 & others. Mitch's compressor bench test

You can also use THIS procedure for testing positive displacement compressors with fixed displacment.

Sounds like you have what is needed to recover the R12 & bench test the compressor. The most likely suspect at this point.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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