AC system rebuilt but compressor squeaks loud-93 940

[rollin_home]

Hi ,

I've just rebuilt the a/c on my 93 940:
- New condenser
- removed compressor and drained the oil then added 6oz of PAG 150 oil (+ 2oz to drier etc)
- replaced all the 'o' rings,
- pressure tested it to 120 lbs with a tank of nitrogen
- vacuumed it out for 3+ hours
- added 2 cans of 134a

But, now when filling and running it after a bit, I hear this squeak coming from the compressor.
The compressor is a Volvo unit with only about 2 years of use max due to condenser got a hole the system sat unused.
When I drained the compressor, about 3 oz of oil was in it .
When I added the new oil, I poured it into the large outlet of the compressor and forced the oil into the inside of the compressor by putting a piece of plastic tubing on the outlet and blowing .

When filling the system it reads 110 PSI at idle, when the compressor comes on it goes down to 50 psi (put 2 cans in ).
But that squeak, scares me. I'm just wondering if that squeaking noise could that be coming from *inside* the compressor, like if it wasn't getting lubrication or somehow the oil isn't where it should be ??
I thought maybe it was belt squeal but then I tightened the belt and it still squeaks.

Also, the compressor gets pretty hot, I cant keep my hand on it, maybe this is normal but I am not sure what a compressor should normally feel like heat-wise.

Any ideas , suggestions ? Did I screw something up ??

Thanks

Tim

[jimmy57]

Did the ground wire get securely installed? I have seen the 4 cylinders with rubber bushed compressors that have to have ground wires squeal with bad grounds. It was cyclic clutch slip due to low magnetic force from low voltage.
50 psi running is high but I assume that it at idle speed and not 1500 rpm.
The arwa of compressor where the discarge from cylinders is fed to exit via the small diameter line (discharge) is going to be hot, that is normal. Compressing adds heat.

[rollin_home]

Hi,

Yep, the ground wire is on tight, the compressor cycles and engages fine.
The 50 psi is at idle.

Can you tell me if my adding PAG oil to the big outlet port of the compressor is the right way to go. I poured the oil *out* of the compressor via that port so I just figured I'd pour it in through that same port. All 6oz of PAG oil didn't want to flow into that port so I had to help it with a little air pressure via blow pipe.

Just curious, how hot does a working compressor get? Mine is too hot to keep my hand on but I can touch it.

Thanks,

Tim

[jimmy57]

Adding to oil to the port is fine. There is no crankcase in that compressor. The oil moves with the refrigerant and will get dispersed in the system in a short time of running. The compressor temp is ambient temp dependent. The discharge from compressor could reach 275 or even higher, the compressor is cooled, when properly charged, by the returning low pressure refrigerant. The compressor goes a little over 200.

Hold the engine at about 1500 with rod between lower seat cushion and accel pedal and then monitor pressure(s). The low side should be 35 if the car is hot inside and outside temps in lower 90's. Have fan on 3rd speed and the control on max cold with recirc selected, and have the windows and doors all closed. The low side should fall as interior cools into the 20's with time. The line from accumulator on pass. side going back to compressor should be really chilly all the way to compressor when charged to correct level. Also after the system runs for a while if you turn fan down to speed 1 the low side should go to lower twenties and then the compressor will go off, low pressure goes up to about 45 and the compressor comes on again. If it is overcharged then it will not cycle. If undercharged it will not hav e that cold line all the way over to compressor.

[rollin_home]

Hey Jimmy, thanks a lot for the help.

I'm glad to hear that the oil circulates with the r134a, so that means that the squeak is not the compressor self destructing from the inside because of lack of oil. I know 8oz of pag 150 is in there somewhere.

I'll need another can of refrigerant, which I need to get . I just don't want to have to open up the system again after putting in $45 of r134a .

Do the bearings or the clutches cause squeaking sound and can they be oiled or repaired with the compressor in the car? I'm just thinking what could be causing the noise and why. Maybe it will go away after a full charge and some use .

Tim

[rollin_home]

OK, some progress.... with 70% charge it produces cool air but the radiator fan won't come on, this cause the system to not cool while the car is not moving and no air is moving through the condenser:

While adding last bit of the 2nd can, I noticed that the electric fan in the 940 wasn't cycling on and this was causing the pressure on the low side NOT to drop. In fact, it ROSE to almost the 'Hazard' mark on the blue gauge (150 psi). Figuring that maybe the condenser isn't getting cooled, I took it out for a test drive and inside the vents blew cool air....great its working! Back at the garage, I put the gauges back on, crossed the leads on the radiator temp sensor and forced the fan to run, then the low side pressure would drop to 30 psi and I added more of can #3 but the compressor wouldn't shut off. I guess it wont run right (cycle on/off) until the full charge of 950grams is in there.

What causes the rad fan to come on/off ? Is it one of the 3 sensors on the condenser or is there another switch somewhere ?? I pulled off the connectors on all 3 condenser mounted sensors and checked them for dirt etc, tomorrow I'll checkthem with an ohm meter and try to figure out the bad one.


Squeaking was fixed by further tightening of the belt ... thought it was tight but those rubber bushings allow some play.

Tim

[billofdurham]

The three pressure switches are colour coded lilac, grey and brown.

The lilac switch is the safety or high pressure shut-off switch
The grey switch is for the engine cooling fan at high speed.
The brown switch is for the engine cooling fan at low speed.

If the cooling fan is not coming on check its relay.

Bill.

[rollin_home]

Thanks for the info on the sensors, thats helpful. I got out my green Volvo book an dlooking at the wiring diagram, I ran the following tests to isolate the faulty component(s):

- crossed the two terminals on the temp sensor on the radiator and the rad cooling fan runs, low-side psi drops to 30 : OK.
- crossed the two terminal in the brown sensor (on condenser) and the rad cooling fan runs: OK.
- if I drive the car and air is moving through the condenser, the a/c blows cold: OK
- ran a/c, car at idle, and low-side pressure rises to 80 psi without rad fan blowing, rad fan does not come on: NOT OK.
- pulled off brown sensor, clipped on continuity tester onto two leads on the brown sensor and put 100 psi air into other side, but the sensor did not close (which turns on fan) : NOT OK.

Does anybody know at what psi the brown sensor should close ?

I am concluding that the brown sensor is bad, as long as the car is moving all will be fine but without the car moving the low side pressure will rise and maybe the system will self destruct from over pressure. What do you think ?

Also, during this testing, the compressor never shut off despite the car windows being closed and the rad fan being run with manual override, a/c blowing cold. What causes the the compressor to shut off in a Manual ECC setup, is there a thermostat or is it done with the pressure sensor (which one)?

Thanks.

Tim

[jimmy57]

brown switch closes at approx 230 and reopens at approx 165.
grey switch closes approx 310.
The thermostat is the pressure switch on the accumulator. It will cut off at 22-24 and back on at 42-45 all PSI.
If you are idling engine then the compressor will not cycle off. all automotive a/c testing is done with elevated idle speed except the vehicles with variable displacement compressors and even those usually have some elevated engine speed for system evaluation. The compressor efficiency is too low for the system to work right unless you speed engine up.
If you run engine at 1500, with the temp on max cold, recirculation button depressed, and the fan switch jumpered in your case at the time, the low side should fall within a few minutes as car interior cools and if you turn fan down to speed 1 it will cycle.
If it is below 80 outside the compressor will cycle on speed 3.

[rollin_home]

Thanks for clearing that up.

So if the brown sensor closes at 230psi , my test with 120 psi is inconclusive and br sensor is probably fine or at least this doesn't prove its not fine.

I'll use 1500 rpm from now on, I know you told me that previously . It should also take a bit more refrigerant, its not yet sucked in the 80% of the last can . I saw one site that said it takes 900grams +/- 50grams . According to that it takes 850-950grams maybe it has enough at this point, at least its close.

Alright, I'll put that brown sensor back in and see how she does. Its probably doing just fine and I can put the tools away.

Thanks.

Tim