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Old 05-26-2017, 02:08 PM
phathom phathom is offline
Join Date: May 2016
Location: Vancouver, WA
Posts: 73
phathom is on a distinguished road
So I did some searching and found that the kicking on at 4k rpms symptom was likely due to low pressure in the system. Our variable displacement compressors use the refrigerant pressure to regulate the displacement of the compressor. This makes sense then. Low pressure would make it not adjust to the right displacement to cool. Revving the engine to 4k would spin the pulley and clutch faster and increase pressure enough for it to work.
So I went to the store and bought another can of r134a. When I started filling it up, the aux fan revved up really high like if I pulled the plug. I filled it up to about 43psi and it seems happier like this in terms of kicking on, but it still isn't really cold like I'm used to, that seems to come and go. Perhaps it needs to be fully purged and then fly charged to spec with both high and low side gauges instead of just using a low side gauge/filler combo. I'm going to see about renting a set of gauges from Auto zone to get it really tuned in, but I think the problem here was definitely the pressure of the system since the clutch was engaging with the ac on and the aux fan was working.
I'll update, but this may be our problem, possibly because we're not used to working with variable displacement internally regulated compressors. Older cars had a fixed displacement compressor, which was much simpler and as long as the clutch engaged it would pump. These require a set pressure to determine the displacement and how much to pump on top of it.

Edit: drove it a bit. It seems to be doing better, especially while moving. I checked the pressure again. When filling it, it was shaky and would go between 43 and 55 as the compressor cycled. After driving and checking it again it's sitting solid at 37psi. I'll see how it acts after it sits for a few hours. That seems to be when it's had problems kicking on.
2006 X5 3.0i
2000 323i R.I.P.

Last edited by phathom; 05-26-2017 at 02:35 PM.
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