2000 XJ AC compressor -- Can I fix it?

[Heavyopp]

So I have a 2000 XJ -- Been sitting idle for about 3 years before I bought it -- I've owned it for 2 years, been driving it for about 8 months

I never really cared about the AC but decided to check it out recently -- Turns out that my AC system is fully charged and didn't leak out in all that idle time

What happens is my ac compressor clutch won't activate -- I do have a full 13+ volts at the electrical connector for the compressor coil -- so the PCM wants the AC compressor to run

Its seems to me that the coil doesn't generate enough magnetism to pull the clutch back -- I checked this with engine running and a carefully placed screwdriver to the exposed back side of the coil on the compressor -- there is magnetic pull, but very little

I have not even tried to see if the clutch is actually free and able to engage the compressor flywheel -- The clutch will spin by hand, not easily but able to move it with force and just fingers

My questions -- Can I rebuild just the front end of the compressor without losing the refrigerant? Replace coil, replace clutch? Any other options like take it off and clean? Lube on moving parts of clutch?

I have a 2000 cherokee -- cali emissions, LHD

AC compressor is Sanden -- Model U 4784

I'm not against sourcing the right compressor and using it for parts -- Is this possible? Worthwhile? Should I just buy a new compressor and bite the bullet and just replace?

Just looking for a little guidance -- Never really cared for AC but since my system holds a charge I'm thinking why not

 

[sidewaysstarion]

Pull the front of the clutch off, clean, remove the spacer/washer and reassemble.

 

[jimbar]

Have you tried the low pressure switch jumper? 9 out of 10 times thats it.

 

[Heavyopp]

Yes I did jump the low pressure switch -- thats not it -- low pressure switch is functioning properly

I have 13+ volts to the wire connector at the compressor -- The PCM is calling for the compressor to turn on, all parameters for proper AC function are met except that the clutch won't engage on the compressor

I think I will try pulling the clutch and clean -- remove the spacer -- I'll be able to see what condition the friction surfaces are and be able to test the coil a little more accurately

 

[Overland]

Clutch assembly with new impulse coil is under a hundred dollars, usually. If you hot wire it to the battery and it doesn't engage loudly, it likely burned open.

It should be pretty audible, especially if the engine isn't running.

 

[Heavyopp]

Clutch assembly with new impulse coil is under a hundred dollars, usually. If you hot wire it to the battery and it doesn't engage loudly, it likely burned open.

It should be pretty audible, especially if the engine isn't running.

Sure but I can't seem to find one...

 

[Overland]

Sanden shows it to be $85. Good place to start.

http://store.sanden.com/index.php/6581-6010.html

 

[Heavyopp]

I been dickin around with that Sanden website for a few days -- couldn't find that

still having a hard time confirming that clutch set is the proper clutch set for the 4784

I did find the service manual a few days ago and saved it -- no part numbers though

I'll play around today and pull off the clutch, see if it's all jammed up and test the coil again by jumping the relay

 

[tech1001]

I've been looking for a new pulley for my a/c compressor but the price is like $85 , just a little more and I can get a new compressor . that's all most the same problem you are having the parts cost to much , and you can buy a new complete one for just a little more .

 

[Overland]

I've been looking for a new pulley for my a/c compressor but the price is like $85 , just a little more and I can get a new compressor . that's all most the same problem you are having the parts cost to much , and you can buy a new complete one for just a little more .

And then evacuate and charge. Not everyone has a vacuum pump or gets r134a as cheap as I do.

 

[Heavyopp]

So I ended up getting some time to myself today -- Managed to get the AC running

Pulled the compressor clutch, clean both mating surfaces at the pulley and clutch with a wire wheel -- this gave the coil much better pull -- I also removed the 1 shim between clutch and pulley -- there was only 1 shim

Works for now, clutch does seem to slip a little when re-engaging but only sometimes -- I'll nurse it along for a week or 2 just to be sure my compressor is good -- hate to buy a clutch kit just to find out the compressor needs replacing

I did find out my electric fan doesn't work -- I have never actually seen it run without me forcing it on -- now I can't even force it on by jumping the relay -- I do have power to the fan connector so, once again, the PCM is calling for the fan to run -- Just ordered a new one from Rock Auto -- I'm done playing around with used fans and hoping they work when needed -- around $45 shipped

I do have a question with the low pressure at higher engine RPM -- My low pressure switch cuts off the compressor at around 2000 RPM -- stays off for a few seconds then kicks back on -- pressures range from around 25 psi to 75-80 psi reading from the low pressure port -- is this normal?

I'm wondering if I have enough refrigerant in the system, Is it possible to read how much refrigerant is in the system without a full set of gauges -- I just have a cheapo low pressure gauge -- What is the proper filling or topping off procedure for the system?

 

[Heavyopp]

I've been looking for a new pulley for my a/c compressor but the price is like $85 , just a little more and I can get a new compressor . that's all most the same problem you are having the parts cost to much , and you can buy a new complete one for just a little more .

Just like overland said -- replace the compressor and most of us need professional help with the refrigerant

I don't want to open that system if I don't have to

 

[Overland]

So I ended up getting some time to myself today -- Managed to get the AC running

Pulled the compressor clutch, clean both mating surfaces at the pulley and clutch with a wire wheel -- this gave the coil much better pull -- I also removed the 1 shim between clutch and pulley -- there was only 1 shim

Works for now, clutch does seem to slip a little when re-engaging but only sometimes -- I'll nurse it along for a week or 2 just to be sure my compressor is good -- hate to buy a clutch kit just to find out the compressor needs replacing

I did find out my electric fan doesn't work -- I have never actually seen it run without me forcing it on -- now I can't even force it on by jumping the relay -- I do have power to the fan connector so, once again, the PCM is calling for the fan to run -- Just ordered a new one from Rock Auto -- I'm done playing around with used fans and hoping they work when needed -- around $45 shipped

I do have a question with the low pressure at higher engine RPM -- My low pressure switch cuts off the compressor at around 2000 RPM -- stays off for a few seconds then kicks back on -- pressures range from around 25 psi to 75-80 psi reading from the low pressure port -- is this normal?

I'm wondering if I have enough refrigerant in the system, Is it possible to read how much refrigerant is in the system without a full set of gauges -- I just have a cheapo low pressure gauge -- What is the proper filling or topping off procedure for the system?

You can read the low pressure and compare it to ambient on a 134 pressure chart, but you won't know what your high side or pressuredifferential is.

Best I can suggest is that you spend seven dollars on one of those thermometers that slip into the vent to check AC performance and add until it reaches the green, or about 45-50°. It'll also indicate when your clutch slips because the temperature will rise and fall.

 

[Overland]

Just like overland said -- replace the compressor and most of us need professional help with the refrigerant

I don't want to open that system if I don't have to

Friend of mine was quoted $150 just to evacuate and leak test, then $40/lb for refrigerant. Vacuum pump and manifold is golden, I fixed him up for thirty dollars.

 

[Heavyopp]

You can read the low pressure and compare it to ambient on a 134 pressure chart, but you won't know what your high side or pressuredifferential is.

Best I can suggest is that you spend seven dollars on one of those thermometers that slip into the vent to check AC performance and add until it reaches the green, or about 45-50°. It'll also indicate when your clutch slips because the temperature will rise and fall.

I have a thermometer I can use -- doesn't have a fancy green safe zone but it will do

Does it matter what the outside temp is when trying to get to 45-50?

Thanks for the help

 

[Overland]

You can compare your low pressure gauge reading to ambient temperature with a 134 temperature/pressure chart in order to assume your charge is correct.

As for the thermometer, your air will seem to work better when it's cooler outside. The chart specifies what your low pressure should be for any given ambient temp.

 

[Overland]

 

[Overland]

Also, you really do need that electric fan in order to get a proper pressure reading. I'd leave it alone until you have it in and functioning.

 

[Overland]

On that note, you should have the control set to MAX AC, fan set to HI, and you can slip a penny under the throttle stop to get 1800-2000rpm.

 

[Heavyopp]

Does it matter what the RPM's are to use that chart -- is it at idle?


You're typing as I was typing -- thanks