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AC Compressor Valve Diagnosis

Old 05-02-2019, 09:57 AM
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AC Compressor Valve Diagnosis

Have a 2005 E320 W211, bought the car used with 96k, has 98k on it now.

AC has worked on & off never really getting cold. AC and vent fan would blow hot in front and cold in back or blow hot in rear when AC is on so I changed the heater exchange valve and that fixed the hot/cold air coming out of different vents when it's not suppose to.

I ran the AC immediately after switching the heater exchange valve and it didn't really work, right tempature air came from the right vents but AC was not cold. Then I drove the car 40 miles after swapping out the heater exchange valve and I put my set of gauges on the car and got some interesting results.

Outside temp was 65F with 50% humidity, according to the chart pressures should be 25-30 low & 49-123 high

Internal car temp was around 80F before starting AC.

1) Before starting car pressures where 67.4 / 77.5.
2) Started car and AC on high, high side went to 350-358 psi in 45 seconds, then fan kicked on high and pressures dropped to 9.5/135.
3) Once pressures dropped, fan slowed down and system stabilized at 26.5/129.4 over about 10 minutes. After stabilizing the Center left vent temp was 42F and AC seemed to be working decent (but it was cool outside).

My question is, what is the normal high side pressure before compressor valve gets signaled to open?

350 psi seems high to me and I'm trying to figure out if the AC solenoid valve is stuck or sticking?
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