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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?
I'm thinking maybe the valve hasn't been moving because the heater exchange valve has been messing with the computer signal to the valve and it hasn't been moving or something?
First testing AC at 65F is not really good starting point.
Than your gauges show 10 psi difference at static measurements, what indicate poor quality.
Lastly high side at 358 indicate good pressure and pressure drop later when car is cold is normal operation with variable output compressors.
The high pressure limit switches on those cars are about 30 bars, so you are not getting there.
I am using build-in sensor for AC testing as hooking up hoses for outside gauges brings risk of another troubles.
Best test is to get the car on hot day to very hot temperature inside and then with scanner observe the high pressure for next couple of minutes.
05-01-2019, 04:38 PM
