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TO FLUSH OR NOT TO FLUSH?????

NKENN on Tue May 19, 2009 11:19 AM User is offlineView users profile

Year: 2005
Make: FORD
Model: 500
Engine Size: 3L
Refrigerant Type: R134A
Ambient Temp: 75
Pressure Low: 50
Pressure High: 225
Country of Origin: United States

Pressure readings obtained @1500 RPMs with automatic climate control system set at it's lowest setting of 60 degs F and the blower set to high. The vehicle doors were left open to keep the A/C demand as high as possible with such a low ambient temperature. The discharge air coming out of the registers on the dash would not go below 70 degs F under these conditions. This system uses a TXV and a variable scroll compressor whose variable capacity function is controlled by a suction pressure sensing device.
When I first tested this system (on my daughter's car) I did not realize it had a variable capacity scroll compressor. I interpreted the pressure readings as Low Side: HIGH and High Side: NORMAL and diagnosed the problem as TXV stuck open (shame on me). I replaced the TXV and the symptoms remain the same. When I replaced the TXV, I found the refrigerant oil that was dripping out of the TXV and evaporator to be very clean tinted orange in color (I assume the orange color is a result of the UV dye that Ford puts into the new systems now).
Now, I am assuming (shame on me again) that the problem is with the variable capacity compressor. I believe there must be some problem with the "variable" function of the compressor and that it is not properly compensating for high demand from the system. I might add that my daughter said the system seems to operate at highway speeds but, the air immediately warms up when she stops in traffic.
My questions are:
1. Is my assumption about the compressor reasonable?
2. If it isn't the compressor, what other component may be causing the problem?
3. Since the oil is clean and there was no evidence of particulate contamination in the TXV, do I need to flush the system when/if I replace the compressor?

THANKS!

mk378 on Tue May 19, 2009 12:06 PM User is offline

After replacing the TXV, did you evacuate and charge to the specified weight of R-134a? Variable compressor systems do strange things when not properly charged.

NKENN on Tue May 19, 2009 12:46 PM User is offlineView users profile

Yes, the system was evacuated and held a "perfect" vacuum. It was then charged with 29 oz. of R134A as specified by tag under the hood.

HECAT on Tue May 19, 2009 1:24 PM User is offline

Quote
Originally posted by: NKENN
3. Since the oil is clean and there was no evidence of particulate contamination in the TXV, do I need to flush the system when/if I replace the compressor?

If inspection of the system indicates all is clean, and the compressor being replaced did not internally fail; many do get away with a successful compressor replacement using the "oil balancing" procedure. IMHO, risky but possible.

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