Q45 R&R AC Compressor

[rsiwicki]

How hard is it to be a DIYer on R&R on compressor? I need a new compressor and if it ain't all that bad doing an R&R on the compressor then I will attempt to do it on my own and then take it to a shop afterwards for a recharge & replacement of the drier also unless I can do the drier myself as well.

[DAEDALUS]

The drier is downright cake relative to the compressor. The compressor isn't too bad, but there is a bolt at the rear that's kind of a pain. Not impossible. 4 bolts on the compressor, plus 2 more for the lines. The drier has a clamp, a harness, and 2 bolted lines. You'll need new o-rings at each line connection. Lube with the appropriate refrigerant lube.

[rsiwicki]

Thanks for the response....I did a search and I don't see where anybody has documented the R&R of the compressor. Do you know how long it would take and would the car need to be on a lift? I am pretty good at basic R&R parts, but not sure about the compressor and if it would be just easier and safer (ensuring that I don't mess up the o-ring fittings) to pay somebody.

[maxnix]

The main thing is you don't want to leave it open for any length of time at all. Not even overnight.

As soon as you get it assembled, you want to evacuate the system of all air and moisture. Now you can test via leak down your connections. If all is well, then commence recharge with lubricant and R134a.

[DAEDALUS]

It can be done on stands, as can most jobs. You need enough elbow room for you and your tools.Time...well, the drier can be R&R'd in about half an hour, maybe a bit more. The compressor might take 1-3 hours, depending on how fast you work. This is kind of in line with book time, which is .6 and 2.5 hours, respectively.I assume you'll have the system evacuated prior to the work. You can install everything except for the lines going to the drier, and leave the lines and drier capped until just before you have it vacuumed and filled.

[Q451990]

Or you could alway buy a vacuum pump like this, and a set of gauges. http://cgi.ebay.com/ebaymotors...43989With 134a you can still buy recharge cans for about $5 each at parts stores or even Wal-Mart.

I used one of these when I replaced the A/C evaporator on my truck. Pulled the compressor and drained the oil per service manual... then recharged after letting it vacuum for about 3 days! (I had other things that had to be done and just let it run until I was ready)

I pulled a vacuum for 15 or 20 minutes with the old dryer in place, and then made sure that it held for a while... just to make sure that there weren't leaks in the system. Then I put the new dryer in and let it vacuum for the long cycle.

I've always heard that you should let it vacuum for 24 hours... but I don't think it's done in the field that way anymore. Way too much lift time...

The system has worked great for the last two years ever since.

Heath

[maxnix]

USe a real commercial grade vacuum pump, not a hobby one. Just won't pull it down enough otherwise.

[Q451990]

USe a real commercial grade vacuum pump, not a hobby one. Just won't pull it down enough otherwise.

Do you think the one above isn't strong enough? I definately would steer clear of the $20 "venturi effect" style ones that operate from shop air, but I think this one would be fine.

Heath

[DAEDALUS]

It's the same kind of pump found in all the shop recovery machines. AC systems have such a small amount of volume, near-complete vacuum can be had in well under a minute. Between minutes 2 and 5 I can't even see the needle move. The amount of atmospheric moisture in one cubic foot of humid Florida air is less than 2g.

[maxnix]

Do you think the one above isn't strong enough? I definately would steer clear of the $20 "venturi effect" style ones that operate from shop air, but I think this one would be fine.

Heath

Probably. Just a general caution against the PMQ approach. One I use is larger. It's the tenths of psi it is able to pull that is critical fro removing moisture.

[elwesso]

Rob, the AC compressor isnt a "condo friendly" sort of thing...

If I were to do it, I would have the system evacuated, then do the R/R, then take it back and have the drier installed. Tech has said 30 mins is generally sufficient to draw vacuum... Then just recharge/reoil!!

[rsiwicki]

yeah....it doesn't sound like a condo friendly job. I will save the job for a mechanic to do and concentrate my efforts on the SLIP light relays.

[maxnix]

Tech has said 30 mins is generally sufficient to draw vacuum...

30 minutes is the minimum time to pull the vacuum.

Better a couple of hours to get those last remnants of moisture.

There is a post by Q45tech worth reading not too long ago.

[DominickJ30]

With 134a you can still buy recharge cans for about $5 each at parts stores or even Wal-Mart.

Defenitely something you do not want to do. It may work as a 'band-aid' in some situations but you never really know how much your adding unless you have a scale etc. If you not experienced in evacuating and recharging A/C Id leave it to the shop to do.

[qship96]

and good luck finding someone who will really spend at least 30 minutes vacuuming down the system! took me 6-7 phone calls/visits with techs at different shops to find one that would do this,as every one else said that 3-5 minutes is enough!everybody is in a rush to squeeze in as many customers as possible I guess.my suggestion is to STAND THERE and watch the entire procedure and make sure the 30 minutes are adhered to and that the system is recharged EXACTLY to specification! my tech tried to tell me that if he put another 10% r134 in than spec,it would cool better-no thanks to that one!hard to be sure operation is performed as FSM calls for as techs have their own beliefs-misbeliefs?

[DominickJ30]

and good luck finding someone who will really spend at least 30 minutes vacuuming down the system! took me 6-7 phone calls/visits with techs at different shops to find one that would do this,as every one else said that 3-5 minutes is enough!everybody is in a rush to squeeze in as many customers as possible I guess.my suggestion is to STAND THERE and watch the entire procedure and make sure the 30 minutes are adhered to and that the system is recharged EXACTLY to specification! my tech tried to tell me that if he put another 10% r134 in than spec,it would cool better-no thanks to that one!hard to be sure operation is performed as FSM calls for as techs have their own beliefs-misbeliefs?

The 30 minute vacuum is really only required for retrofits. If it is a leak 10-15 minutes will be more than enough time to boil off any moisture. Thats why they only do it for 3-5 min.

[John Nordling]

Here's another question about the process. I read the service manual procedure about replacing the compressor on my '90 Q. It includes a process that collecti the lubricant in the system so you can tell how much to put in with the new compressor. Here's the question: If your system is leaking lubricant, how do you determine the correct amount of lubricant to add with the new compressor?

Another question: How good are local parts store rebuilds? Any good sources out there???

Thanks.............John in Seattle

[DAEDALUS]

You can't measure a leak, but you may be able to estimate it. I mean, if it isn't dripping, and there's only a small oil spot, I'd guess not much leaked out. But if it's dripping you can't assume anything.My rebuild lasted 5 years. If they all did I'd call it a wash vs. OEM for what they cost. If you're not certain how long you'll have the car a rebuild might be a better choice. I chanced it again with another one off Ebay (not installed yet). If and when this one goes I'll probably spring for an OEM one. When I bought this one I had already given the rest of my money to Joe.

[maxnix]

The 30 minute vacuum is really only required for retrofits. If it is a leak 10-15 minutes will be more than enough time to boil off any moisture. Thats why they only do it for 3-5 min.

Q45tech:

"Member's standards vary."

Mine are greater based on technicians with cumulative centuries of experience with refrigeration systems.


Modified by maxnix at 5:37 PM 7/19/2005

[DominickJ30]

Q45tech:

"Member's standards vary."

Mine are greater based on technicians with cumulative centruries of experience with refrigeration systems.

Mine are based on personal experience...

[Q45tech]

The exact time depends on the strength of the vacuum pump used [brand new or worn out or somewhere in between] what vaccum the pump pulls in microns.

http://yarchive.net/ac/vacuum_pumps.html

The microns in "microns of vacuum" refers to microns of mercury. There areabout 25400 microns in one inch of mercury.

25 microns is the standard.........1/1000 of inch of mercury.

The major problem is the oil in the system and how it absorbes water and how slow it is to release the water...........why you ALWAYS replace the dryer EVERYTIME you open the system.............even for 10 minutes!

[dwhitty]

There are A/C shops in Miami that replace the compressor with a rebuilt one and recharge the system for about $400+. Changing the compressor yourself is not that hard but if it can be done for the above price then I would use the shop.