Repairing My Disassembled AC System

I am intimidated by this job; I have never done any AC work before. Last year I thought I was going to get my AC working, thinking it just needed some basic service. Then I discovered that the compressor is actually missing. I do not know the condition of the other pieces, except that I believe they are present.

How many beers are required for this job of installing a new compressor and then figuring out after that how to hook up and troubleshoot everything?

I don't absolutely need AC, but it's nice on the summer days to have it if I need to drive my kids anywhere. My one-year-old doesn't need to suffer for her father's love of raggedy old American cars.

Flush would be prudent. New compressor, new accumulator, new orifice tube. Hoses if they aren't there! New gaskets on the back of the compressor (they are cheap, but they will be included with a hose set). Fill components with appropriate amounts of oil per FSM. Buy a pump and gauges from Harbor Freight. Pull vacuum. Hold vacuum to ensure no leaks. Charge per FSM chart (around 2500rpm, it will take about 2.5 cans). AC is no tougher than any other job on cars once you know how things work.

Hi Jay, and thank you. Part of the problem is probably that I don't really understand how it all works. Doesn't sound too crazy the way you described it. How do I flush the system? In terms of hoses and compressors, would you recommend a certain brand?

I see on Rockauto they must have twelve different compressor options, including two differnt styles that look nothing alike. One is very short, the other much longer. What's the difference?

Bull wrote:

Hi Jay, and thank you.  Part of the problem is probably that I don't really understand how it all works.  

Read this: http://www.buickforums.com/forums/showthread.php?t=26737

Then return with any unanswered questions.

Bull, you need a HD6 compressor. I'd replace the hoses either way while you're replacing the rest of the parts.

buickwagon wrote:

Bull wrote:

Hi Jay, and thank you.  Part of the problem is probably that I don't really understand how it all works.  

Read this: http://www.buickforums.com/forums/showthread.php?t=26737

Then return with any unanswered questions.

I'm on it!

200OZ wrote:

Bull, you need a HD6 compressor. I'd replace the hoses either way while you're replacing the rest of the parts.

Might as well, right?  What about the coil in front of the radiator?  Evaporator?  I did learn subsequent to my post that I need the larger type of compressor.  It is odd that Rockauto shows the smaller type under '95 Roadmaster 5.7 listings.

I found a old post on here in which people talked about "kits" for our cars on eBay. I found one with new Delphi compressor, orifice tube, oil, seal kit, and expansion device for something like $260. Still would need hoses, refrigerant, and tools! My d actually has a vacuum pump somewhere in his garage. He also has manifold sets, but I don'tnow if they would work. He did residential and commercial HVAC.

Residential stuff will not fit the cars. Make sure the condenser (in front of the radiator) and the evaporator are not leaking before you assemble anything. Then clean them thoroughly before assembling anything. Check Rock Auto for pricing before you buy a kit, It may cost less from Rock Auto.

If you assemble it correctly, you should not have any leaks, but you probably should check it.

There is a redneck way of getting the air out of the system. My brother does it this way...put a can of refrigerant in the low side, and run the system for 10 minutes...vent the high side, and add some more refrigerant...repeat,  then fill it with a low side gauge (available on some cans of refrigerant) and you should be good to go.

Fred Kiehl wrote:

Residential stuff will not fit the cars.

But you can buy adapters. They probably won't have a scale showing temperature for R-134a, but will have a pressure scale so you can use an R-134a temperature/pressure chart.

The manifold set from Harbor Freight is not as heavy-duty, but good enough for occasional use by the backyard mechanic. And cheap enough that it might be almost as cost effective. Their single stage vacuum pump is similarly suitable, and venting refrigerant is illegal. New hoses are far cheaper than proper flush equipment. The condenser takes a lot of abuse, being in front of the radiator. It cannot be flushed (it's parallel flow) so if there is any question that the compressor is missing because it puked it's guts into the rest of the system, I'd replace it.

All told, the cost of the tools and parts is less than you would be charged by a shop to do this repair. And if you buy the tools, you will have them for other cars in the future.

So if I install new hoses, compressor, condenser, accumulator etc. there will be no need to buy a flush kit, correct? The parts inside the firewall don't need to be flushed?

I said the technique was redneck, and I do not know that the word legal appears in the description of redneck.

So, I only just realized after popping the hood that there are two sets of hoses for the system. One set bolts to the back of the compressor and one bolts to the firewall. It seems that the ones for sale on eBay and everywhere else are the ones for the compressor. Are the other lines just never replaced, or rarely?

I never really scrutinized the components of the system before.

Bull wrote:

So if I install new hoses, compressor, condenser, accumulator etc. there will be no need to buy a flush kit, correct?  The parts inside the firewall don't need to be flushed?  

It should be impossible for debris to reach the evaporator under the dash. The refrigerant first passes through the orifice, which incorporates a screen. Even if debris did somehow make it through and lodge in the evaporator would then be captured by the accumulator. If debris was somehow sucked backwards out of the compressor, it would have ended up in the condenser, which you plan to change. So you can safely skip flushing.  

The cheap flush kits are not worth the money and will void your compressor warranty. If you decide to flush you need semi-professional supplies to ensure warranty coverage. Hecat seems to be the cheapest solution that is still covered by some manufacturers warranties. An alternative is to install a suction screen to protect the compressor. The last post in that link I provided earlier has some suggestions.

And yes, the compressor hoses probably take the most abuse. The hose from the condenser to the evaporator (which contains the orifice tube) is protected from debris by the orifice tube. The other is from the evaporator to the accumulator and is unlikely to contain any debris for the same reason.

Excelent.  So no need to clean those other hoses if resuing them?

I am excited to tackle this now, but the initial cost outlay is harsh.  As you say, though, less than a shop would charge and I will gain knowledge and some new tools in the process.

I'm going with Delco for the houses, and a new but unknown brand compressor kit from eBay. They have good ratings; found a link on the Impala board. About $40 less than the Delphi kit.

Any advice about condenser brands? Delco is a lot more than Spectra or other brands. Since Delco stuff is Chinese now, am I paying for quality or just the name?

I just read your info abou flusihing.  Very informative.  Should I go ahead and add a filter while I am doing this?  Would you recommend that?  Where would I install it? Wouldn't it eliminate the need for a new condenser?

Fred Kiehl wrote:

I said the technique was redneck, and I do not know that the word legal appears in the description of redneck.

Sorry if that comment sounded unduly critical, and for the record I find it perplexing that releasing refrigerant is illegal while using the same gas as a propellant in a paintball gun or asthma inhaler is fine. Whatever the reason, it's a practice you may not want to advertise.

I don't know that the word redneck implies "illegal" either.

Originally denoting unionized miners on strike (who wore red neck scarves for mutual identification), it has come to be generally applied to any manual labourer -- particularly those working outside and subject to a sunburned neck such as farmers -- a class of people noted for their ingenuity and resourcefulness in accomplishing a job with limited resources in an unconventional manner. I respect and identify with those people. (I am also aware that the term has been corrupted into a derogatory implication of ignorance, bigotry and stupidity, which I feel is unwarranted).

The technique you describe is better known as "purging" -- using refrigerant to dilute the air in the system. It is more effective than not purging, but not as effective as evacuating. There will always be some air and moisture remaining, even after several purges. The air will reduce the effectiveness of the system, the moisture can cause acid formation, corrosion and premature failure. A few extra cans of refrigerant may be cheaper than a vacuum pump, but if you think you might do more than one car eventually, the pump pays for itself compared to wasted refrigerant. Even redneck farmers buy tractors, right?   

Bull wrote:

I just read your info abou flusihing.  Very informative.  Should I go ahead and add a filter while I am doing this?  Would you recommend that?  Where would I install it?  Wouldn't it eliminate the need for a new condenser?  

The filter I chose for my own car is mentioned in the last post of that thread. It is inserted into the line from the evaporator to the compressor, right at the compressor. I installed the filter instead of changing the condenser.

However, my condenser was only a few years old and in excellent condition. If yours is battered and bruised from years of gravel and bug strikes or corroded, etc. you may prefer to just get it over with and change it now. Particularly since the system has sat opened for an unknown number of years.

This thread is close enough to my own situation..
I had to get my system filled a couple of times over the years and now the compressor broke. It feels strange to turn, the cluth broke, and the pulley bearing makes bad noise. It looks to have leaked oil.

I ordered the compressor, accumulator, condenser, seals and o-rings, compressor suction and discharge hoses, orifice tube, and a filter screen. I'm going to replace them myself.

I was going to get the evaporator and its hoses flushed by professional shop before putting in new orifice tube and connecting old parts to the new parts. I thought that even if there are no metal shavings past the orifice tube, it would be good to get all of the 20 year old sticky stuff out of the system. But that would cost pretty much... you'd say that would be a waste of money? Should I just put everything together and get it filled instead?

Another thing is the oil. FSM only gives typical amount each component is holding, and says to fill compressor by the same amount that comes out from the old one. But how about if the compressor has leaked? For some reason, FSM doesn't specify the total amount. If the compressor leaks, and the oil circulates with the refrigerant, can I assume there is less oil in the evaporator than normally, also? How much oil I should pour in each of the new components, in the case I don't flush the evaporator+lines, and in the case I do? The link to spec list pdf , that scoffman posted on the basic priciples of auto ac sticky thread doesn't work. Thank You, buickwagon, for that awsome writeup, btw!!

Very little oil is retained in the evaporator and hoses -- maybe 1/2 an ounce. A bit too much oil in the system will reduce efficiency slightly but will not cause any harm. Too little oil in the system can cause premature wear to the compressor. So I personally err on the side of caution. In your situation, I would add the full oil charge divided 1/2 in the compressor and 1/2 in the accumulator whether you flush the evaporator or not. IE: 4oz in the compressor, 4oz in the accumulator. The oil charge should be listed on the underhood sticker, but if that's gone I'll attach a copy of that spec PDF to this post. Apparently I can't do that here. So I'll host it and provide a link: AC oil and refrigerant capacity charts



Don't forget to rotate the compressor by hand a few times after final asssembly and before starting the engine. You might need a clutch adjustment tool to do so, they can be pretty stiff when new.

Thank you for that info, I'll do just that!
What do you think about the necessity of flushing?

Well, I know some people swear by it. And the industry makes a lot of money doing it. But here is my reasoning when I replaced my dead RMW compressor a few years ago:

1. Unless you have the proper equipment, you can't do it properly. That's not cheap.
2. Using improper equipment is worse than not flushing.
3. There some disagreement between manufacturers as to what constitutes "proper equipment".
4. You don't need to flush new components.
5. Debris can't get past an undamaged orifice tube (filter). Or past an accumulator (trap).
6. Debris could theoretically flow backwards into the compressor supply hose, (although it would take a catastrophic failure to induce sufficient flow.)
7. Replacing the hoses is cheaper and easier than (proper) flushing.

So, if one replaces the hoses and the accumulator and the orifice tube and the compressor and install a suction side screen, then one has replaced all the places debris is likely to hide, plus one is protecting the compressor from the unlikely event that there is some small particles left in there.

Accordingly, I did not flush mine. The following spring, I recovered the refrigerant and inspected both the orifice tube and the suction filter. Neither exhibited any debris. The system has been running strong for 3 years now.

But that's me. Your Mileage May Vary.

I think I'll go this route too. We'll see, how it turns out...
Just started disassembling. The orifice screen appeared intact and had caught flakes.

I'd like to jack the right side of engine up a little to get the compressor bracket nut off. Is it a strict no-no to lift it by the oil pan?

I would not jack the oil pan! That rear nut is a PITA to get out (and back in again), but can be done from underneath with a couple of extensions and a u-joint.

One tip I read about (after I did mine -- so I haven't personally tried it yet!): After the compressor is out, remove the entire rear bracket and turn the compressor mounting hole into a slot by notching with a hacksaw or grinder. Apparently the 96 cars came that way from the factory, and it's much easier to reassemble since you can then start the nut on the stud before putting the compressor in place.

Feeling your pain, man.  Had a shop replace the compressor, condenser, and evaporator.  Now it needs new lines.  Ugh.

Thanks, Michael!
And thank You, buickwagon for all your help!

I managed to get the compressor rear bracket nut to turn by an ordinary socket (not a deep well), a u-joint, and a long extension. There was just enough room to turn it without the joint binding. It came off with the stud, which made the compressor come out pretty easily. Will definitely grind the hole to make it an open slot.

New compressor says it has PAG46 inside, so I guess that's what I'm gonna use...

Compressor instructions tell how to replace some switch:
http://www.rockauto.com/info/577/Compressor_Switch_Removal_and_Installation_Instructions.pdf
I guess that's not needed with our cars? Is that the same thing as the compressor cycle switch, which our cars has on the accumulator? The new compressor has those o-ring held blanks, whereas the old one has just two recesses in the casting.

Also, the old compressor has some screwed in valve-like thingy at the middle of the back face, whereas the new one has nothing. Is that a pressure relief valve?

It looks like you bought a generic multi-fit type compressor, with provisions for a variety of applications. The high pressure switch is on the line in our cars, so don't worry about it.

Ok, it's working!
I screwed up unbelievable many times, but at least it's working now... and I've learned a lot.
A couple of tips:
- a new condenser may already contain an orifice tube
- the ac delco filter screen fits in original hose, but may not fit in different brand reproduction hose

I got GDP hoses. I remembered the screen after I'd bolted everything up. I then detached the hose at the compressor and tried to install the screen. I did not believe it wouldn't fit, since I had test fit it to the old hose. I tried to force it. I couldn't install it and got some some aluminum shavings from the manifold into the hose. I could not get all of it out. I didn't want to swap the old, dirty hoses back in. That was my biggest screw-up, and I'm still a bit worried about it. Hope it keeps on working...

I got the system vacuumed and filled at a local shop.

BTW, my system was dry as Sahara. Not a dropping of oil came out of any of the components. I think the compressor had been trapping oil from the flowing refrigerant and leaking it out. I don't think the FSM procedure of substituting the amount of oil that comes out of the compressor with the same amount when swapping the compressor makes any sense. Well, it makes sense, if there are no traces of leakage, but if you have to replace the compressor, it's probable the system has leaked oil...

andy caprice wrote:

Ok, it's working!
I tried to force it. I couldn't install it and got some some aluminum shavings from the manifold into the hose. I could not get all of it out. I didn't want to swap the old, dirty hoses back in. That was my biggest screw-up, and I'm still a bit worried about it. Hope it keeps on working...

1. How worried are you about this?

2. Did you happen to measure the actual ID of the replacement hose?

If we knew, for example, that your hose id is 0.489" - 0.497", then we would know that you need 44551-80 instead of 44551-10. I have a few of all the available sizes. If you are worried enough to take it apart again, then PM me with your address and I'll mail you the right size screen.

Oh, and congratulations on getting your AC working again. I agree with your comments about the oil -- better safe than sorry and better a few extra ounces of oil than not enough!

Thanks for the offer! I'm not worried enough to do that, though, especially because I didn't measure it, and because I think most of the possible harm is probably done already.

Thank you!