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Discussion Starter · #1 · (Edited)
Hello all,

Thanks for the recent help with head gasket issues. That was an adventure, to say the least.

As we're now hitting the warmer weather in Seattle, of course my A/C decided to go on the Fritz (what does everyone have against Fritz, anyway? Seems like a decent enough guy...).

I am blowing luke-warm air with the temp set to 65*. Checked the fuse/relay, all is good. Ran a direct current from the battery to the compressor and it fired up. So, I'm either low pressure in the lines or the pressure switch -- right?

I ran a test light on the pressure switch and found that only one of the four 'prong holes' (excuse me as I don't know the technical term) gave me a light. I'm not certain if that's proper, honestly -- but doesn't seem right. I've also been reading that the O rings sometimes go bad on Subies, and I've been trying to figure out how to test that without bleeding R134 if indeed any is still in the system.

My plan was to go to my local auto parts store, pick up an A/C pressure test & neon dye kit. If I've got pressure, then I guess I know it's the pressure switch... but if I don't, I figured I could run the leak test through to see where I'm bleeding out.

If it is the pressure switch, does anyone have any idea how hard it is to replace? I am a novice mechanic -- and have done a lot of work on my other cars (and I've done a fair bit of the simple stuff such as radiator, etc on this guy). I don't have much experience with A/C though and I usually leave the bigger jobs to my local Subie mechanic. Am I getting in over my head with this, or would it be a pretty simple fix?

BTW: I apologize if this is posted somewhere else. I did a quick search and turned up nothing directly related.

Thanks in advance,

Mike
 

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Discussion Starter · #3 ·
swap out the blue ac relay with another blue relay to make sure you are getting enough current to the ac clutch.
Thank you, sir. I did test the relay with a voltometer to make sure it was still okay and visually inspected. Do you think it would still be worth testing?
 

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Please be careful with the test light, to avoid frying the little climate control ECU underneath the right side of the instrument panel.
 

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Changing the pressure switch shouldn't be too difficult, but you do have to remove (evacuate) the 134A refrigerant from the system in order to do so.

If you are going to do things by the book (i.e. legally), then you need to have the AC system evacuated by a shop first... plan on something between $40-80. You can't simply vent the refrigerant to the atmosphere without earning the ire of the EPA. Then again, I'm sure we've all done something illegal at some point that the feds never found out about.

If you do replace the pressure switch, you also will need to pull a vacuum on the lines, which means a $100+ vacuum pump (and not the venturi POS that Harbor Freight sells that hooks up to your air compressor). You'll also need dual manifold gauges to test/verify vacuum and pressures... this is another $60-100.

You can try to do things on the cheap, but I will forewarn... AC systems can be very finicky and even the tiniest bit of ambient air or moisture can make your situation much worse.

All that said, I recommend at least getting a single manifold gauge and testing the low side pressure. If it's lower than 28 psi and the compressor isn't turning on, it's probably not the switch. If it's over 38 psi and the compressor isn't turning on, it's could be the switch, a relay, or a open circuit somewhere. Anything in between, add a little bit of coolant (just enough to get to around 40 psi) and try again.
 

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Discussion Starter · #6 ·
Psygnal, thank you for the detailed response. I think this may be something better left to the pros, if it is as finicky as you say. I am definitely more toward the novice side--I know enough to be dangerous, but I don't really want to 'bubba' this job.

The sad thing is, I am already $5,500 into this car in the last year. Whoever gets it next is getting a brand new vehicle... lol.

That said, I ran a pressure check to the 'low' side and -- lo and behold -- the shop that last worked on the car over-filled the R134. Could that also cause the issues with the compressor not coming on? It's currently sitting at somewhere north of 55 and south of 100 PSI (mid range of the 'red' per my gauge).
 

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There is a very well regard member over at subaruoutback.org that regular repairs AC without pulling vacuum.

Gary even chimes in over here every now and again.

"Truthfully I have A/C gauges and a vacuum puller - and I don't even use them. Just not worth my time. I've repaired so many Subaru a/c's and had them last 50,000 - 100,000 miles it's just not worth my time"

Read this thread:

See http://www.subaruoutback.org/forums...efrigerant-repair-5-less-15-minutes-less.html
 

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Sure, you can do it without the gauges and vacuum (especially if you plan on selling the car afterwards); it will work, but not to spec unless you purge the air and moisture from the system post-charge, which can be done, but not legally. The first time I did AC work was simply an off-the-shelf 134A recharge kit... ended up overfilling and blowing the compressor. The second time I bought that crappy device from Harbor Freight... it worked, but the compressor cycled too much to get decent cooling in temps above 85 degF. The third time I did it, I put a vacuum on it for an hour, charged the system by weight and used the gauges to verify pressures... it's worked perfectly since.

I don't question Gary's expertise at all, but his situation is a bit different than the OP's. Since we're dealing with potential pressure switch issues, manifold gauges are a must for a proper diagnosis.
 

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Turns out that it was a relay after all. Back in action in time for the summer :)
I had the same issue last summer - tried switching relays and it didn't work - bought a new relay and it works perfectly.

Actually, I bought 2 relays since it seems to be a common failure point, I'll be ready next time :)
 
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