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AC compressor repair without opening system

33K views 90 replies 13 participants last post by  gordo999 
#1 ·
Compressor locked up and started smoking from the center shaft.

I heard grinding noises but is it possible it was the pulley or bearings grinding on the clutch as opposed to insides getting torn up?

Is it possible to replace the entire clutch assembly without removing the compressor and having to vacuum and recharge refrigerant?

If the insides were getting torn up, would I be able to tell from this approach?
 
#52 ·
babblefish said:
Now I see it, small line (high pressure?) and large line (low pressure?) connected together.
This is probably way too much information for what you want but it has taken me a while to figure out how an automotive AC system works on my Safari and I thought I'd share it in case it interests anyone.

Any corrections would be appreciated and you can call me a science troll if you like. :lol:

If you had a garden hose with water flowing through it and you had a fixture on the end of it like the orifice tube you'd get a spray, right? The pressure of the spray would be lower than the water coming down the hose as well.

When a compressor compresses the low pressure refrigerant gas into high pressure, the gas become a high pressure liquid. Butane gas can be liquefied at 75 PSI if temperature = 42C. R134a has a boiling point of -26C, meaning it converts to gas at that T at 1 atmosphere pressure (14.7 PSI).

If you raise the pressure of the gas enough, it remains as a liquid till a higher temperature. If it's already a gas, it reverts to a liquid.

The high side of the compressor can hit 200 PSI at least and 200 PSI is 13.6 atmospheres. At that pressure, the boiling point of the gas will rise to over 300 C, therefore it is in a liquid state coming out of the compressor high side. When the gas is compressed to liquid state it's temperature increases.

The liquid maintains it's high pressure through the condenser but as it loses heat in the condenser to the environment, the pressure drops a bit. The line coming out of the condenser is regarded a high pressure line so the refrigerant should still be in a liquid state as it reaches the orifice tube.

Maybe someone with experience could indicate what pressure to expect at the Shrader valve in that line.

For those interested in math:

Ideal gas equation: PV = nRT

Don't go away, it's easy.

P = pressure, V = volume, n = number of molecules of gas, R = gas constant, T = temperature

the volume is constant due to running through a pipe and so is the number of molecules (provided you keep your refrigerant at the correct level).

therefore, equation can be written P = (nR/V)T

since nR/V is constant, while P and T vary, it tells you P varies proportionately with T. In English, if the pressure goes up the temperature goes up, and vice-versa (provided the volume and weight of the gas remain constant).

Note that P varies with the number of molecules (essentially the weight on a planet like Earth) and if you let the weight of the refrigerant get too low, the P drops in proportion. That messes with the operation of the entire system.

When you compress the gas in the compressor, P goes up and T goes up in proportion. However, going through the condenser, the liquid refrigerant loses heat to the environment, therefore P goes down a bit as T drops. That would depend also on the outside environment, how hot or cold a day it might be.

At the orifice tube, it's still liquid, and if you opened that Shrader valve just before the brass nut, 'BRIEFLY', which you should not while the compressor is running, it would shoot out a liquid mixed with green PAG oil.

Don't ask me how I know. All I can say is that a good amount of pressure can remain in that line even with the gas bled out of the low pressure end, so be careful.

Besides being illegal to vent R134a into the atmosphere it's also very dangerous. This gas is seriously toxic in sufficient quantity and could kill you if enough is inhaled.

At the orifice tube, what's left of the liquid is atomized into a spray at lower pressure for entry into the evapourator. In the evapourator, the spray receives heat from the cab air and turns back into a low pressure gas as it expands in the evap. From there, the LP gas goes through the accumulator where dessicants dry it out. The accum also stores excess PAG oil, or whatever is used in the system.
 
#53 ·
So that switch in the back of the compressor, my original one is larger in diameter than the opening on my new compressor (see photo).

The new compressor is a UAC CO 20144C so I assume I need to buy a compatible switch, correct? Or what would happen if I didn't replace the switch?
 

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#56 ·
97cargocrawler said:
Nope, its not. Pull that aluminum plug out of the new compressor!
Doh, thank you! Well the long weekend gave me a chance to install the new compressor, accumulator and orifice tube. Allow me to recap the journey and my ultimate question this round will be... Is it safe now to vacuum and recharge?

Where it all began
Locked AC clutch and pulley. Barely got home with a smoking compressor.
Hoping just the clutch assembly needs to be replaced, but more reasonable minds reminded me these parts have been working for 21 years.
Decided to open the system, hoping my compressor wasn't shooting metal shavings throughout the system.

Checked for metal shavings
At the compressor inlet...
IMG_3657[1].JPG


...and the compressor outlet...
IMG_3656[1].JPG


...and after pouring solvent into the compressor, letting it sit for several hours, and pouring it back out...
IMG_3688[1].JPG


...and the orifice tube...
IMG_3654[1].JPG


...and the oil from the accumulator...
IMG_3697[1].JPG


The presence of metal shavings was very very minute. I still wonder whether there are chunks at the condenser (where the metal would have gone first) but that seems like a bear to check, but I'm gonna consider this adequate due diligence.

New parts are in
New compressor (UAC 20144c $140 from Amazon).
Came filled with 8 ounces of PAG 46 oil.
Old pressure switch moved to the new compressor (lost steam on searching out a new switch).
Electrical not yet plugged in since I don't want the compressor to kick in yet (zip tied to the oil filler for now, at the top of this pic)...
IMG_3712[1].JPG


New orifice tube and accumulator.
Added 3 ounces of PAG 46 into the accumulator since I have rear AC (per instructions from the compressor).
Old switch moved to the new accumulator. I can upgrade later since this doesn't require opening the system.
IMG_3711[1].JPG


Haven't recharged yet, but successful test drive! I have my van back on the road. So finally, this comes back to my question.

Other than flushing, which I realize comes highly recommended but I just don't have the energy for and I am gambling my lines are "good enough", am I ok to vacuum and recharge?

And another side question: In my last photo, the top half of my evaporator cover has crumbled off and it was suggested that I might want to cover it up with some reflective material. Any further info on why an evaporator cover is needed and how I might address that?

Thank you all! Hopefully I'm nearing the finish line with summer coming around the corner.
 
#57 ·
Your picture of the orifice tube looks like the smaller end has most of the filings on it.. Was it in backwards? That small part should be facing down, arrow facing down with the refrigerant flow. Other than that it looks very normal for the age of it.

Also stock oil is 150 but if your compressor states 46 you should be okay if you got all the other oil out. Or at least if you got most of it with changing the compressor and accumulator. Keep in mind a little will remain in the rest of the components. So if you have 8 plus the 3, plus a couple ounces left over youre a touch over but probably be just fine.

I'd vacuum it out and if it holds steady then fill it.

Evaporator cover is for heat insulation from the engine compartment. Mine crumbled a bit when I replaced my evaporator but was mostly in one piece so I reused it.

Scott
 
#59 ·
Thanks. The more input I get, the more I get confused... I think I need to stop asking questions!

sfeaver said:
Your picture of the orifice tube looks like the smaller end has most of the filings on it.. Was it in backwards? That small part should be facing down, arrow facing down with the refrigerant flow.
My old orifice tube was installed correctly, small part down, but that is an interesting observation... there is grit on the "output" side as opposed to the "input" side.

gordo999 said:
The orifice tube looks cleaner than mine was but I don't like the look of that grit on the smaller intake screen. There is a chance that a sac containing the dryer material in the accumulator has ruptured and spilled some of the drying material into the system.
If this is the case, I guess the dessicant would have had to flow with the refrigerant through the entire system (compressor, condenser, evaporator) before reaching the orifice tube... and I'm wondering if that's likely.

Don't know what to say or think, just posting this up in case there are other thoughts.
 
#61 ·
Jawon said:
New parts are in
New compressor (UAC 20144c $140 from Amazon).
Do you mind sharing the shipping costs. The price sounds decent ( I presume $US) but I'm concerned about shipping costs to Canada.

With regard to firing it up it has to be your call. I don't think anyone is going to advise you to do so without flushing the condenser and evap.

Note on the evap cover. It is sealed to keep engine heat out of the evap area. You want cab air in the evap so it can suck the heat out of it. Insulate it the best you can. I think you can get insulation foam.

I would not trust the 8 oz PAG oil in the new compressor. I was advised to dump it out and measure it exactly. Now that it's assembled, there's not much you can do. Many manufacturers put a minimal amount in the compressor to keep it lubed. Did yours specify it had 8 oz in there when shipped?

There is a device you can put on the accumulator Shrader low pressure valve that measures the amount of oil in the refrigerant. The one I had was not great. It has a sponge in it that soaks up the oil and you can tell by the length soaked by oil approximately how much is in there.

On page 55 of this PDF, at the bottom page you can see the requirements for PAG and 134a for a Safari with and without rear AC. Note the difference in PAG oil ''TYPE' between the Harrison and Denso models. One uses PAG 150 and the other PAG 46. Yours is a Delphi.

http://www.4s.com/media/4981741/Four-Seasons-Capacity-Guide.pdf

The important thing with R134a is to get the moisture out of there. There are instructions for how to draw a vacuum to do that.
 
#64 ·
Staying on topic :)

gordo999 said:
I would not trust the 8 oz PAG oil in the new compressor... Did yours specify it had 8 oz in there when shipped?
Yes. You can just barely see what it says on the sticker.

Ok so now y'all have me thinking about flushing. The system is sealed but the system is not vacuumed and the compressor hasn't been running so I believe that means the new oil in the compressor and accumulator have still not moved.

Could someone provide some more specific direction on what parts to flush and how to disassemble? For instance I can't even see how to access and remove the input hose from the condenser. If it's a reasonable job I may consider.

I don't have access to an air compressor so would flushing be a waste of time?
 

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#65 ·
Jawon said:
Yes. You can just barely see what it says on the sticker.
Did it say what type of PAG oil? There are several types as far as I know and each has a different viscosity.

Here's advice from Delphi auto parts, although I don't know if they are the same Delphi marked on your compressor.

https://www.delphiautoparts.com/en/toolbox/why-oil-balancing-critical-when-replacing-compressor

http://www.aa1car.com/library/pagoil.htm

It says in the article that if you use the lighter PAG oil when a PAG 150 is called for, the compressor will be noisy and may fail sooner.

Jawon said:
Ok so now y'all have me thinking about flushing...Could someone provide some more specific direction on what parts to flush and how to disassemble? For instance I can't even see how to access and remove the input hose from the condenser. If it's a reasonable job I may consider.
On my 2001 Safari I had to remove the front grill with the GMC on it. Looking at the van from the front, the high side comes in from the compressor on the top right of the condenser and the output is on the lower left with a vertical tube coming up from the bottom of the condenser.

I removed the entire condenser, it's only 4 bolts if I remember correctly.

You likely won't get many replies because all this has been covered in other posts on this blog and even in this thread. CC gave a good description of flushing and the equipment to use. I had to dig through the Net, on Google, for advice but I have forgotten much of it now.

Also, there are purists and the practical type. I read of people using varsol to flush but I know varsol leaves an oil residue. I suppose you could follow the varsol with a flush using 99% isopropyl alcohol, since it dissolves oil and evapourates quickly. I lean toward doing things the right way but sometimes what I need is not available or is far too costly to justify...like buying a proper compressor for blowing air. Even if I splashed for one I have nowhere to keep it or use it.

I did not have a proper compressor either but I have a small 12 volt compressor for tires and it blew up a tire requiring 60 PSI in a few minutes. I rigged an adapter for it out of an old vacuum cleaner nozzle and used some 1/2" clear vinyl hose I had laying around that fit over the condenser inlet pipe.

You could even use a heavy duty sized bicycle pump, the kind with the ears you stand on. However, you need a good connection so you don't need to balance the condenser while you pump. It's pretty fragile in ways.

The thing is to improvise. This is not a job to undertake if you're not willing to improvise. When you improvise you have to take responsibility for anything that ultimately goes wrong. The more you can do it the right way the better your chances of the compressor lasting. It's not just the compressor cost and the hassle, if you have to replace it again there's the refrigerant cost and the accumulator.

I am certainly not going to advise you on a proper way to do the job. I'll offer information but it's up to you whether or not you run the compressor without flushing the condenser and the evapourator and check the connecting lines. It's a chance you take.

What you are facing with R134a is a highly corrosive product that forms between the refrigerant gas and water vapour. That product could be right through your system, however, the fluid you ran out of your accumulator was green and looked pretty clean. Maybe you got lucky and had no corrosion inside your system.

If you're looking for metal in the fluid run a strong magnet through it. The oil pan cover on the Safari differential has a magnet built into the cover to pick up metal sludge.

I could not find the proper flushing agent here in Canada and I used some xylene I had from a paint job I did once. Xylene is a solvent used in laboratories as well as for thinning paints for a sprayer. It's also highly flammable and you should have a good respirator for the fumes.

I flushed till the black was gone and I was getting clean xylene through. I was not sure if xylene leaves an oil residue so I ran 99% isopropyl alcohol through. It dissolves oil then evapourates. If you pour in half a bottle then swish the condenser around, provided you have removed it, the alcohol should get any oil residue dissolved.

I looked for carbon tetrachloride, or chlorethylene, because it does a super job of dissolving oil/grease then evapourating quickly. It's used in brake cleaners. Could not find any readily available. I wasn't about to waste $8 for a spray can that could barely blow an ounce in the condenser.

Beware: don't breath in the fumes, get a good respirator.

Blow it out into a rag, with a catch basin below, till the liquid is all through then keep blowing till the vapour blows through. It should dry out quickly on its own. I did the evapourator as well but it was pretty clean.

If you smoke, I don't recommend it around that stuff.
 
#66 ·
It would have been much easier to flush the system when it was apart. I recommend only Flushing the condenser and the evaporator at this point. If you flush the hoses you will end up with a bunch of the flush substance stuck in that muffler and the accumulator which won't be a good thing and you obviously don't want to flush your new compressor.

If you take things apart and only flush the evaporator and the condenser coils you won't be losing much oil and you will probably be flushing out the areas that have the most crap stuck in them since you already replaced the compressor and the accumulator. The minimal amount of crud in the hoses probably won't affect anything. The coils should flush rather easily with low pressure so you should be able to buy a pressurized flush can and just use that. Depending on where you decide to flush the front condenser coil you may need to remove that orifice valve so as not to plug it up. If you decide you want to just go lazy at this point you'll probably be fine too. There is a filter supposedly in the accumulator that might catch some of that stuff and there is the screen on the orifice valve. Worst case scenario you would have to open it up and clean it out later or it might just work fine if you're lucky. I don't think anything will get damage from having those little particles in there.

You definitely need to draw vacuum on that system before filling it.
 
#67 ·
Need troubleshooting help.

Got new compressor, accumulator and orifice tube installed.
Old switches plugged into compressor and accumulator.
Vacuumed for 45 minutes. No leaks.
Hooked up the refrigerant.
Started the van with AC on.
But compressor won't kick in.

I'm assuming it's electrical related. Or maybe not? Could someone please suggest troubleshooting steps? I'm very uncomfortable with electricals.
 
#68 ·
How many cans of refrigerant? One can goes in with the engine off. Get up to about 50psi. The the remainder go in with the engine on and ac set to max. The compressor should start to cycle after the first can is in. I always put my cans in a bucket of hot water too while I'm filling. Makes the process wayyyyy faster.
 
#69 ·
Jawon said:
I'm assuming it's electrical related.
You did plug the compressor cable back in, right? If so, check to make sure it's seated correctly.

Like CC said, you need pressure in there before the compressor will kick in. If the pressure is lower than the low pressure valve on the accumulator requires it won't turn on.

If you have adequate pressure and it still won't turn on there's a way to short the low pressure switch to see it it will turn on. Don't recall exact procedure but you need to disconnect l/p switch and short the harness plug.

You could pull it back a bit and check for continuity across the switch with motor running and switch connected. Careful not to get meter leads caught in fan belt, :D Or your tie.

Since your compressor was overheating, check fuses and AC relay.
 
#73 ·
Argh.

Compressor plugged in.
Vacuumed to near 30 inches.
With engine off I got in some refrigerant by opening up low and high side (see below 35 psi low side).
Won't go up anymore. I did lose a little refrigerant from the can messing with the piercing valve that I didn't quite understand.
Turn engine on, open only low side.
AC is on but compressor does not kick in (waited about 5 minutes).
AC/heater fuse is ok.

Now what? I appreciate all the help. I thought I did the appropriate research but I feel like a bonehead
 

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#74 ·
Add another can. Close both valves tight and be sure to momentarily unscrew the hose going from the can to the manifold (yellow) at the manifold connection, to purge the air that got in between cans. Just until you hear some escape then tighten the hose again. Try to remember that between each can. Its not critical but good practice and lets you know the can is pierced.

I dont think 30psi is enough. You should have about 50 from the first can. Keep filling. Use a bucket of hot water like i mentioned.
 
#75 ·
Success! It's all done.

Well it turns out it was the can tap and/or the self sealing can that was plugging back up. After initially piercing the can, refrigerant flowed fine but after about a minute it stopped. I would have to pierce again and play with the valve to keep the flow going.

I got the can tap below at O'Reilly's and the refrigerant from Walmart for $9 per 12 ounce can. Maybe this little road bump was the price I had to pay for going cheap!

So I had four cans and just sat there babysitting the valve. Eventually got it all done. All seems to be well now and hopefully there will be many more years before AC work is needed again.

One more question though. What can I do with my old compressor and accumulator? Just give them to the metal recycling fellas? And for the cans, I don't think I paid any kind of deposit but it says I can return them for a refund???

Thank you thank you thank you for everyone's input! I learned a lot
 

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#76 ·
I use that same valve. Works great for me though I did have one of those cans fail to dispense. Only CA charges the extra $10 per can. You won't get a refund if they didn't charge you the fee already.

Cut that accumulator open and show us if there's desiccant inside! I'd love to finally answer that question. But yeah, it's all scrap otherwise. Melt it down and pour it into an ant hole.
 
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