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Old 07-11-2018, 03:46 PM
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EricSilver EricSilver is offline
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Join Date: Mar 2000
Location: Fairfax, VA
Posts: 1,322
OK, my numbers, using the Harbor Freight manifold:

Conditions:
Engine - Hot
Ambient - mid-90's

Final Readings:

Compressor Off
High Side: 150 PSI
Low Side: 150 PSI (presumably; needle moved into the "retard" zone)

Compressor Initially Engaged
High Side: Surged to 325 PSI then Settled back to 240/250
Low Side: Surged to 50 PSI then Settled back to 48

Compressor Running A While -- Idle
High Side: 250 PSI
Low Side: 48 PSI
Evap Temp: 58

Compressor Running A While -- 1500 rpm
High Side: 240 PSI
Low Side: 48 PSI
Evap Temp: 58

Other Relevant Info:
When I first hooked up the manifold, the high/low readings repeatedly oscillated up and down in opposite directions: High between 215 and 275; Low between 45 and 50. Did not matter whether at idle or 1500 rpm.

Suspecting over-fill, I attached a large, cold, empty r134 can to the yellow hose and vented what I could. After that, I noted the oscillation stopped. I disengaged the compressor, let the high/low equalize, then reengaged and the pressures remained constant at the above-reported 250/48 high/low.

My question now is, can I still be over-filled? And given the 58 degree evap reading, is it possible I have a faulty sensor? (About a week ago, I noticed the evaporator temp,at one point, was a degree or two higher than the heater cores (in the 60's) which should be impossible, correct?

Quote:
Originally Posted by Diseasel300 View Post
Throwing a manifold gauge on there will speak volumes. If the pressures are good, your problem is in the control system somewhere. If the pressures are out of whack, you know you need to adjust the charge. I wouldn't trust the electronic readout from the CCU further than I could throw the whole car. If you have any one sensor that's skewed, the readout is completely meaningless.
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