Low Side High High Side Low

[JimnJudi]

Hi all, new member here. I have a 2008 Outback 2.5 basic with 57,000 miles. The previous owner was a little old lady who seldom drove so it sat in the carport all the time. The compressor kicks on/off every few seconds and the vent temps are in the low 60's (outside temp 85). The condenser was clean so I tried adding a little R134a but that didn't help, so I bled some out (yes, I know, but it was only a little) and the compressor stopped cycling and stayed on, but the temps stayed the same. I figured the cheapest and easiest repair was the expansion valve so I bought a Denso valve, desiccant bag, and a set of gauges and had my mechanic recover the refrigerant. I replaced the parts and all o-rings, vacuumed down to -30, let it sit overnight to verify no leaks, then let the pump run for two hours (it's a two-stage pump). I then added 411 grams of R134a (sticker under hood says between 369 and 425g). The low side maxed out, the high side was 155 and the quick cycles resumed. The specs say the range should be around 25 psi to 220 psi. I'm thinking a weak compressor but wanted to hear other opinions.

Thanks in advance.

[Cornbinder89]

Doubt it, the compressor is cycling, and the high side is above what static pressure would be for the temp. What do you mean by "low side maxed out'? Give a pressure reading and what happens to both the high and low side pressure when the compressor cycles. Time to stop throwing parts at it and diagnose. We may end up trying some part like a pressure transducer, but that will have to wait until we know more. Are condenser fans coming on?

[King-of-DIY]

Sounds like an internal compressor seal problem to me.
I rebuild my own compressors but I'm getting old and dog gone if I don't seem to forget things soon after doing it.

But that problem would cause me to suspect the compressor.

[Cornbinder89]

Not me, and without pressure reading and temps, condenser fans working or not, everything is a guess. It is very rare for a compressor to "wear out", they fail from lack of lube, seize etc, but wear out? not likely.

[King-of-DIY]

Not me, and without pressure reading and temps, condenser fans working or not, everything is a guess. It is very rare for a compressor to "wear out", they fail from lack of lube, seize etc, but wear out? not likely.

I can't argue with you and I will assume you are far more experienced than I.

That said.....I've been inside them enough to know that is definitely one of the common symptoms.

A common cause of this issue, that you didn't mention, is simply having a compressor sit without use for an extended time.
I've seen vehicles that had AC problems where the Ac was not used for over a year, then an evap replaced.

Problem is, the compressor seals dried out internally and would not seal on restart.
The internal seals are often large O rings but can be smaller, bearing type seals. All will eventually harden from non use.

Again, not disputing your expertise...just adding a humble bit of mine :-)

[Cornbinder89]

Its been over a month, and the O/P hasn't been back since he posted.
Seal leak doesn't cause a compressor to fail, it just leaks, again a compressor that can make pressure is not likely to be faulty. More and complete diagnosis is required, but it is unlikely the compressor is the fault.