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      01-10-2026, 07:33 PM   #1
vize128i
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Drives: 2009 BMW 128i
Join Date: Apr 2024
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Intermittent A/C

Hello,

I've been stuck trying to diagnose some A/C issues with my 2009 BMW 128i. I notice my A/C fails to cool when the car is idle, likely because the fan doesn't kick on even when I press my A/C button. I've manually turned on the fan via Protools and DME controls, so I know the fan is working -- and it kicks on when the motor temp gets too high I think it triggers at 115-130degC.

I went to a mechanic to fill up the A/C system to the correct levels and even replaced the expansion valve just in case something was going on there. Haven't noticed any leaks and over the course of several months I have no reason to believe there are any leaks since the pressures haven't changed much on the low side (a/c was filled in the summer when temps were close to 40 degC). I have a UV light and have not seen any leaks in the engine bay. Leaks may be hard to spot with the evaporator but I still have refrigerant in the system and the high side holds pressure throughout the months.

Now, I tried to document all my findings today with the following gauge readings:

Outside Temp: 14deg C.

Car turned off gauges connected (no e-fan, no a/c)
Low-65 psi
High-80 psi

Car running (e-fan running, a/c)
Low- 45psi
High- 150-175psi (then fan kicks off and drops down to about 125psi, low side climbs as this happens).

I have also attached a video showing what happens. Would appreciate some insight here, this has stumped me for months.

I don't know if I should consider a new compressor (because it kicks on when I activate my A/c and pressure builds). But something is not allowing my high side to build up pressure past 175psi or so (is this because of a faulty pressure sensor?)|

Video showing the issue below:
https://youtube.com/shorts/mN7pfRYx7aA?feature=share
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      Yesterday, 11:22 PM   #2
vize128i
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Drives: 2009 BMW 128i
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I checked the pressures again today it was a little warmer.

Ambient Temp: 28deg C.

Car turned off initial reading:
High:125psi
Low:~125PSI

Car running A/C Turned on,E-Fan running:
High: ~175PSI
Low:55psi

Car running A/C off:
High: ~150PSI
Low: climbed to 85PSI

Turned A/C back on:
High:150PSI climbed to 175-180PSI
Low:55PSI

A/C Still on, sprayed condenser with water
High :~150psi
Low:~45 PSI

Last edited by vize128i; Yesterday at 11:24 PM.. Reason: spelling
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