A Question About A/C Compressors

[BonzaiDuck]

I'm almost at the end of my SUV restoration. [And -- many regular forum members will know already which SUV that may be.]

At 190,500 miles, there are only about three things that can now go bad on my Trooper: The power-steering pump, the steering gearbox, and the AC compressor.

With an old-car DIY obsession coupled with only limited mechanic experience with a small number of vehicles, imagination can play tricks on you. You may hear a noise or noises while the car is running, and begin to think a component is beginning to die.

And noises are always touted as signs of an AC compressor going south. So I began to search for the parts costs and options.

The 95 Trooper AC compressor is still available through the Missouri Isuzu parts depot -- for $928. That's a lotta cheese, for a 26-year-old vehicle and its AC compressor! Reman compressors can be had for between $200 and $500.

There is also the junkyard option. Going by the Isuzu part number, the same compressor is used in vehicle years from 1994 through 1997. And this isn't for just the "Trooper LS" or Trooper in general. There's the 96 Acura SLX, the Honda Passport, the Chevy Trooper -- all rebadged Troopers. In addition, for the same years, the same part number identifies the compressors on Rodeos and Amigos (one, the other or both -- I'll have to check again). Some junkyard options specify a mileage, and show pictures of the vehicle from which the compressor was harvested. That's something you might want to know. You might not want an AC compressor from a vehicle with front-end accident damage. I've seen these junkyard offerings for about $50.

NOW -- let me be clear. I began to worry about this "noise". It would occur at idle when the engine was warm and the AC turned on. It was a cyclic clatter. Looking in the engine compartment, it only seemed to be coming from the compressor. But I finally thought to put my stethoscope on the compressor, and there ain't no noise, sound of bad bearings or anything else coming from it. It's just fine at 190,500 miles.

I'm beginning to think this almost unnoticeable noise is something like a loose heat-shield bolt or nut. You can't hear it sitting inside the car with the window closed. Most people wouldn't notice it at first. I notice it because I'm DIY-obsessed-neurotic -- on the verge of declaring my vehicle 100% perfect after 26 years and 190,500 miles. It's something that can probably be detected with the car on a lift, and fixed with a crescent wrench.

After conquering my imagination about the compressor, I now see I could buy a couple or three junkyard compressors, possibly for a total of less than $200.

What I want to know is this. Is it possible to bench-test an AC compressor before installing it? It seems that the labor costs could range around $500. You also would want to replace the drier -- a $20 item -- and the condenser, which would cost under $100. If you used a junkyard compressor, you wouldn't want to spend the money on labor if the compressor turned out to be defective. And it would be silly to do the labor yourself, without the facilities for extracting the refrigerant. Or just as silly -- ask your mechanic to retrieve the refrigerant so you could replace the parts and then bring it back for a refrigerant charge-up. You'd pay a mechanic with the proper facilities to do the whole enchilada.

You may ask "why do you want to do that, when your compressor is working just fine?" Well -- for the same reason that I updated my audio system with a strategy for keeping the 12-CD-changer and digital receiver, but began to weary of the changer throwing errors when switching CDs. Last year, I found the original OEM changer at EBay for $80 -- new in the box. I bought it. I recently installed it, and it all works fine -- so pleased I am with my audio-system retrofit strategy and still having a 12-CD changer.

So I could see picking up a junkyard compressor and setting it aside.

 

[Sgt. York]

Why not buy a junkyard A/C compressor, a rebuild kit and rebuild it on your kitchen table? You could take it a step further and buy your own A/C vacuum pump for a hundred bucks and do your own swap.

 

[BonzaiDuck]

Why not buy a junkyard A/C compressor, a rebuild kit and rebuild it on your kitchen table? You could take it a step further and buy your own A/C vacuum pump for a hundred bucks and do your own swap.

Yes -- that's a good idea. If I once successfully rebuilt a carburetor, I timidly suppose I could rebuild a compressor as well. So I'll take my time to shop around for the compressor, buy a rebuild kit for it. There shouldn't be any hurry, as long as the AC system continues to perform as it does.

I was just looking at the factory shop manual -- Heating and AC are in the first chapter and section. There is a bracket between the compressor itself and the engine. So I suspect that the clatter could be coming from a loose attachment bolt or something similar. Even so, if I eyeball the compressor when it's running, there's no wobble or anything to suggest it isn't solidly attached . . . I'll have to get underneath the car, after putting it up on jack stands. Right now, this is a PITA for a 73-year-old: I've had a week of "bad days" with constipation, gas and abdominal pain. I get worn out changing my 95-year-old Moms' disposables and absorbent pads, running the house kitchen and all the rest of it.

As for the A/C vacuum pump, if that's all they cost, I could look into the possibility.

My brother who holds title to our 95 Nissan hardbody pickup, and I as well, both agree that his pickup's AC is frosty in the cab, while mine is a bit limp in comparison. It's "sufficient" even for living in So-Cal, but I can tell the difference between the vehicles. It was worse until I "found" my current mechanic/repair-shop and had them service the AC last year. They discovered that the system had been overcharged with the HFC-134a refrigerant, and you could feel the improvement immediately after they set things straight.

Then, the other day, I saw an ad on TV for interior or passenger compartment air-filters, and began to think the Trooper also had one, but the factory manual shows nothing of that sort. Perhaps the evaporator core fins are clogged with crud? I can't say at this point.

The problem with DIY: DIRTFT -- doing it right the first time. At least, retirees have a lot of spare time. But not so true of retirees with 95-year-old Moms to take care of . . . and Bro -- disabled -- can't be on his feet for more than a half hour.

At least, with the pandemic constraints, I actually have to find reasons and excuses to drive the Trooper.

On the up-side, I'm paying off the mortgage on my Virginia property next month, which means that we can replace the truck with another auto-trans vehicle (for Bro's left-foot problem). Then, the Trooper can be out of commission for days or weeks at a time as I make it 100% "purrr-feck". And - heck -- we may even keep the truck. Sometimes you need a truck . . .

 

[BarkingGhostar]

I would first determine where the failure was. Yes, running the compressor with not refrigerant in it will freeze the compressor and ruin it. But as Sgt. York said, buy a pull a part compressor after you determine the real point of failure (usually the condenser), fix it, then have it tested for leaks under pressurized air with a dye additive. I can't speak of all vehicles but many of the old ones I had the condenser was in front of the car's radiator and the first thing to take a road strike from a pebble or rock. You can pull that part, too, and have it pressure tested.

 

[BonzaiDuck]

I would first determine where the failure was. Yes, running the compressor with not refrigerant in it will freeze the compressor and ruin it. But as Sgt. York said, buy a pull a part compressor after you determine the real point of failure (usually the condenser), fix it, then have it tested for leaks under pressurized air with a dye additive. I can't speak of all vehicles but many of the old ones I had the condenser was in front of the car's radiator and the first thing to take a road strike from a pebble or rock. You can pull that part, too, and have it pressure tested.

Sure -- the prevailing wisdom says to replace the condenser when replacing the compressor and receiver/dryer. if the old compressor were failing, it throws metal shards into the system that get caught in the condenser. But this compressor seems to be working fine.

I will soon have to remove the grill in front of the condenser anyway, because I'm going to re-align the front bumper and bull-bar/grill-guard -- a matter of a quarter-inch off-center because of a damaged bumper reinforcement that I previously straightened with a hammer and anvil. I've collected parts for that over a few years -- new bumper reinforcement, new back-bar, about $80 each. [This speaks to the myth of unavailable parts for an orphaned make and model. The Isuzu depot didn't have the back-bar three or four years ago, showing it priced at about $150. Suddenly, they had it for the price I paid.]

I don't think there was ever any damage to the condenser, but there could be crud in the fins. Easy enough -- too-day! -- to get out there with a hose and see if blasting it with water dislodges anything.

The "new" repair shop and mechanic -- very reliable and bent on saving me money -- serviced it last year, as I said. There are no leaks, because -- as I also said -- it had been over-charged with 134a for a few years!

This is always the burden with the "used/old-car strategy" of ownership. As the owner and driver, one is always bent on staving off disaster before it happens. Even a good repair shop will advise -- "If it ain't broke, don't fix it."

Take, for instance, my episode with the new mechanic last spring. I had used Blue-Devil at 1/3 the recommended dose to eliminate a small Dexron-III leak, and was stunned at how it worked almost too well. I wanted it "outta there". The tranny was, perhaps, overdue for a flush, but my guy looked at the fluid on a white paper towel and told me "you don't need to do it". I didn't tell him about the Blue-Devil. But he told me how he extracts the fluid from the dipstick port, and I realized that all I needed to do it myself successfully was 1/4" refrigerator ice-maker tubing to modify my $20 extraction pump. I kicked him $50 anyway for the good advice.

 

[ISAslot]

If you don't want to invest in a vacuum pump, Autozone allows you to rent them for 'free'. You just put a deposit down, use it, return it, and get your deposit back.

 

[BonzaiDuck]

If you don't want to invest in a vacuum pump, Autozone allows you to rent them for 'free'. You just put a deposit down, use it, return it, and get your deposit back.

I use both AutoZone and O'Reilly's, and I knew Autozone rents tools, but didn't think of it. Thanks -- it's an option.

My Moms kept her '83 Corolla until 2016, when we turned it in to the state of California under "Cash for Clunkers". When she had her full mental faculties, you could've handed her a screwdriver and she wouldn't have known what it was. She used independent mechanics to service the Toyota. She was apparently such a nice lady that she never got cheated.

But I believe that effective used/old car ownership almost requires a DIY effort, even as much as one still needs a reliable mechanic shop. The owner isn't likely to work on more than a dozen cars in his lifetime, and probably a smaller handful. So there's a trade-off between tool purchase and ownership versus necessity. I've had tools in my collection for as long as 20 years which I acquired on the fly -- picking them up as impulse buys or opportunities from the $2-dollar hardware tool table, and didn't find an opportunity to use this or that tool until, say, the last few years.

Of course, someone else here may have said in another thread that doing your own oil changes and other maintenance means you can buy more of those "special tools" -- which is also true.

 

[BonzaiDuck]

After going out this morning to get our monthly cash at the bank, I conclude three things.

First, the odds significantly favor the "cyclic clatter noise" is not coming from the AC system.

Second, the AC is working well and throwing frosty air into the passenger compartment. It's just not as frosty as my Bro's 95 hardbody truck' AC.

Third, the noise isn't getting worse. It depends on the engine RPMs and seems to occur at idle around 750 RPM. It comes and goes. Sometimes, you can turn on the AC and the noise begins to occur. Sometimes, you can turn off the AC and it goes away. And sometimes, the noise occurs with the AC off. If, as a child, you used clothespins and playing cards to give your bicycle a "put-put" noise, that sort of describes what I hear.

Anybody else would probably fail to notice it, or just choose to ignore it. I'm neurotically obsessed with the car after I spent the summer on my projects described in other threads.

My mechanic knows that I'm a nitpicker. I'm planning to take the car to him before Xmas so that he can lube the points on the body as specified after so many thousands of miles in the shop manual. Maybe he can find the noise and fix it. Maybe I can find it in the meantime myself and fix it. I'll have to wait and see . . . .

Next, I could tell you about the plan to paint the SUV roof. It could go another ten years without paint, but I hate having a car with perfect paint everywhere except on one body panel -- which! -- you cannot see from the street! It will cost me $300 for paint and supplies to do it myself, or $1,300 if I pay someone to do it.

Obsessive. I know . . . .

 

[maluckey1]

OP, Just like others have said above, you can pull your compressor, disassemble and inspect it. If it's damaged, you can always go another path, otherwise you can rebuild it.

There's not much complexity in the mechanical portion of A/C systems. I've rebuilt three A/C systems on three different vehicles. I was apprehensive at first, but found that once the wrenches turned, it was not bad at all.

You do need to replace the dryer and also vacuum it down, if you plan to not redo it in a couple of years. Rent of borrow the equipment to save storing extra gear in the garage for the next decade.

M.

 

[deadlyapp]

If you're getting an RPM adjusted clatter, I suspect that your AC clutch is going bad or one of your idler rollers in the belt system is going bad. It's not always a visible issue but there can be dry rot, bearing issue, etc.

 

[BonzaiDuck]

If you're getting an RPM adjusted clatter, I suspect that your AC clutch is going bad or one of your idler rollers in the belt system is going bad. It's not always a visible issue but there can be dry rot, bearing issue, etc.

I don't think the clatter is coming from the compressor or its clutch. I put my stethoscope on the compressor and there's not even a "smooth-as-silk" sound issuing from it. I still have to confirm with my 24"-probe-stethoscope, but I think the noise is being transmitted from the other side of the engine. It's not the power steering pump; it could only be the alternator -- by process of elimination. I continued the explorations of this thread on another about Remanufactured Alternators.

Yeah -- if I replaced the AC compressor, the drier-receiver is a $20 item, and the condenser should not need replacement unless I hear sounds coming from the compressor -- and I don't hear any.

I do notice -- with the "bonnet" open and the AC running -- that the switch controlling the compressor clutch has a nice loud "click" to it, but that's not likely a symptom of anything wrong. I don't think so, anyway . . .