Damn ac compressor knocking again

[Legacy777]

I swear these things are pieces of crap....that or I've just got tons of luck and get the crap ones.

The last two I've had, have left oil slime on the hood. Like the main shaft seal is bad or something. I don't know.

It was fine, and I drove it last night and it was knocking pretty bad. I'll check the charge level, and maybe dump some oil & refridge in.

I've got another compressor waiting when this one dies. I'll probably just buy myself a vacuum pump. That way I can do all my own ac work.

[vrg3]

:!:

You're having bad luck with these things.

Have you flushed the system out? I don't remember you mentioning it. You might have some of the black death in there. That could cause them to repeatedly die.

I also remember the first time around the amount of oil you put in was less than what Subaru's retrofit instructions say... what did you do the second time around?

You should definitely do the work yourself. I've said this before, but you can build a good vacuum pump out of two refrigerator compressor motors.

As far as I know, there's no good way to actually check the charge level... the only way to know you have the correct charge is to evacuate and recharge with the correct amount.

But, yeah, you could just try tossing in a can of ester oil charge (the little cans that have ~2 ounces of oil and ~2 ounces of refrigerant to carry the oil) to see if it quiets down.

[Legacy777]

Yup I thoroughly flushed it out last time with a/c line flusher stuff. If I have to do it again, I may just go your route and use brake cleaner.....hahaha

Second time I put more oil in because the compressor I have is from a 90 MY, and according to the haynes book I have, requires more oil.

Where would I find the refigerator compressor motors, and how would I rig this up? I'm all for giving it a try if I can find the parts cheap, and know what to do.

Yeah I'll see about getting a small can of oil and see if the bitch shuts up....

[mikec]

Josh, if you find time, would you be able to post / PM me the numbers for a 92?

I'll probably end up picking up that book, but while I'm thinking about it.....

Thanks

[professor]

as for a cheap vacuum pump, rather than using two refrigerator compressors in series, get a rotary style compressor out of an air conditioner. GE has this style for sure as well as many others. The fridge compressors are round shaped and don't pull vacuum down to low pressures nearly as well as the rotary pumps.

The rotary pumps have the physical proportions of a beer can but twice that size, rather than the spherical shape of the pancake style. Many thrown away air conditioners should have compressors that work fine. And they are easier to haul home to play with compared to a fridge.

Just cut the lines with a tubing cutter and you can figure out which is which later (one will blow and one will suck !!!) Fit up a ball of rags loosely to the blowing end to avoid getting compressor oil shot into your face. Add a little oil each use, the pump will eject any extra in short order.

Air will be removed 99+% easily with any shitty pump, but to get water, heat up the engine bay first by running the car, then leave the vacuum pump on for a long time. You have to pull down pretty far to get the water. Any left after this will be sucked up by the drier no problem.

[professor]

I guess I didn't make that too clear, with the air conditioner you can just cut the refrigerant lines, and leave the compresser right where it was, in the air conditioner, and just plug it in. Much safer than jerry-rigged power cords and such. On most units the compressor will run full-bore if on "high" "max" whatever and lowest temp setting. At worst you may have to bypass the switch / timer.

You will toast the compressor at some point, at which time you place the whole thing back into the garbage from whence it came.

[Legacy777]

water boils off in a vacuum. So as long as I pull a strong enough vacuum for a certain amount of time, it'll be fine.

[WRXdan]

Easy solution: move up to IL. Not long from now we will have 20 below wind chills

[professor]

better to have it warm, water is a stubborn bastard and may not boil off if it is cold...at the pressures a junk compressor can produce.

if you have a rotary vane lab vacuum pump or commercial AC evacuation pump feel free to ignore this advice

[vrg3]

Yeah, brake cleaner seems like pretty much the same stuff anyway. Just be sure to blow it all out with compressed air afterwards.

The retrofit instructions I have from Subaru (they're the same ones as in the End Wrench articles) say to use 236cc (or 8 fluid ounces) of oil in all Calsonic retrofits.

Refrigerator compressor motors are pretty easy to find... just call up some appliance repair shops; a local store actually just gave me one. You could also try buying a broken fridge -- a lot of "broken" fridges actually just lost all their refrigerant. I actually found mine on eBay, but it's hard to find a good deal there because they're heavy to ship.

One fridge compressor doesn't pull a good vacuum, but two in series work easily well enough for A/C work. My manifold gauges have a humidity indicator and I watched it go from pink to blue as the vacuum boiled out the moisture. If you use the engine's heat to help like professor suggests, it works fine. I ran the engine with the hood down while leaving the pump on for half an hour.

You can prove to yourself that a pump boils water by hooking it up to a sturdy clear container full of water.

All you do is turn them on like professor said and note which is the inlet and which is the outlet. The ones I've played with usually had two inlets, one of which was sealed (I guess this is a service port?). Just connect one's outlet to the other's inlet, and leave the extra outlet open to the atmosphere. You can then pull a vacuum at the inlet.

Refrigerator compressors don't spew too much oil out, but you do periodically need to add some. I just poured a little bit of ester oil in the inlet before each time I used the pump. I put ball valves on the extra inlets for this purpose.

[entirelyturbo]

You can prove to yourself that a pump boils water by hooking it up to a sturdy clear container full of water.

Well, that's just physics. You can get water to boil almost at freezing if you want if you get the pressure down far enough. The point at which water boils depends on the pressure around it, not necessarily its temperature. At sea level IIRC, water boils at 100ºC or 212ºF.

Josh, don't you think you should just break down and buy a rebuilt compressor? That's what I'm going to do once I get around to it.

[vrg3]

Well, that's just physics.

Right -- that's the whole point of evacuating the A/C system with a vacuum pump.

What I was saying is that if you build a vacuum pump out of two refrigerator compressor motors, you can prove to yourself that it's sufficient by boiling water with it.

I don't think the problem's been multiple bad compressors. From what I understand, a working compressor usually doesn't just fail because it's old. Usually it's somehow starved of lubrication, contaminated with debris or moisture, or hydrolocked.

[entirelyturbo]

Sorry Vikash, I needed to make myself feel smart for a minute

Lemme ask this, does one short period of knocking render the compressor useless? Or is that just a little extra wear and tear? Maybe the compressor that's been sitting in my car unused for the past year and a half is still good!

[vrg3]

I think it depends on the cause of the knocking and the severity. I know some people have told me their compressor was knocking and a can of oil charge fixed the problem... I don't know for how long though. I don't know exactly what causes the knocking.

I suppose you could see if yours is workable by slowly pouring a little oil in while turning it by hand. If you can get it to smooth out it might be okay.

[Legacy777]

I put the can of oil in. Didn't do a damn thing. The pressures look ok. low side was around 35, and high side was around 175.

The haynes ac book mentioned that a knocking compressor is probably an issue with the compressor itself.....duh!

Other thing I noticed was that the high side needle was fluctuating a little at times. Also there is what looks to be black goo/oil sludge all around the face of the compressor. This is where the previous compressor was leaking/having issues. This seems to be a pretty normal occurance.

I'm probably going to just drive it till it dies. I'll be taking the car out tomorrow, so we'll see how it does.

I may contact the ac people that I think are associated with cvaxles and talk to them. I'm getting sick of replacing compressors.

[vrg3]

Why would both compressors fail the same way?

Is it possible that you're tightening the belt too much or something? I'm just trying to think of what might stress the crank seal excessively...

[Legacy777]

I have no idea. I'm not sure that this is their mode of failure. The oil and crap spitting out is just a symptom. I noticed the crap on the bottom of the hood pretty much right after swapping in the compressor. So it might have just gotten worse.

[Legacy777]

I called these guys today
http://autoaircompressors.com

It's $199 to pretty much rebuild the compressor. I've got another compressor, that I could send to him. I don't remember the part #, but the calsonics are all swapable between the MY's correct.

I'm debating whether it's worth the money to send it out to have it rebuilt, or just slap the other one on, since I don't drive the car much.

Decisions...decisions.....if I didn't live in Houston, it'd be an easy answer.....but a/c is almost needed all year round.

[vrg3]

Yes, they are all swappable. I'm using a used 90-91 Calsonic compressor in my 93. And in fact, if you look up the 92-93 Calsonic compressor part number in Subaru's computer, it tells you to use the 90-91 compressor.

$199 is a lot... but a 12-month/12,000-mile warranty might be good since your car seems to be eating compressors.

I'm still concerned that there's something weird about either your pulley/belt stuff or the rest of your A/C system that's causing trouble for these compressors. A properly lubricated compressor just shouldn't fail so fast!

I dunno... if you get/build a vacuum pump, changing compressors becomes a really easy task, and you can buy them pretty cheap. For the cost of the rebuild and the professional installation (of which they'll likely insist on seeing proof before honoring the warranty), you can do a lot yourself with used compressors.

[Legacy777]

Yeah that's sort of my feelings as well. I could probably get three used compressors for that price.

I didn't even check out the warranty thing.

I think some of the issues might be that the seals might be old or so-so, and when converting to 134a, it might not like it....I don't know.

It's possible that this one wasn't charged properly from the get go and helped with it's demise.

I don't know if I mentioned, but this one just started knocking one day. Gave no previous slight knocking. It was maybe a little noisier then the previous, but didn't seem to knock.

I'll see how it holds up tonight after a good drive.

[vrg3]

These Calsonic compressors were designed at a time when it was expected that they would be retrofitted to R-134a at some point in the future... I would think the seals would be meant for it too.

Maybe it has to do with the type of ester oil you're using.

Maybe you should try using PAG oil -- what Subaru recommends -- for one round. Flush the system out, put in a new receiver-drier with PAG oil, put in a compressor with PAG oil, evacuate it for at least half an hour, and charge it yourself so you can be sure it's done right.

My stock compressor also just started knocking one day with no prior warning.

[Legacy777]

Yeah I could try PAG oil and see how it holds up. You have to use the high viscosity stuff right?

I think I'm just going to go that route.....I don't feel like spending 200 bucks on a rebuilt compressor

[vrg3]

The viscosity should be ISO 100. I think they make both lighter and heavier oils than that, so I guess it's a medium viscosity.

You've probably already seen them, but these End Wrench articles are relevant:

http://endwrench.com/images/pdfs/InsiderACRetrofit.pdf
http://endwrench.com/images/pdfs/AC.pdf