Automotive Air Conditioning Information Forum

By chance does this belt power any other device(s)? If so, does that device have an issue perhaps?
I ask because... take your brain OUT of AC mode for a moment...
Years back I had a customer with a Mitsubishi that kept throwing and breaking alternator belts and it made me crazy, time after time.
Then one day I had it on the lift, belt intact, and reached up and grabbed onto the alternator only to discover that it was smokin' hot! Nearly burned myself.
I said, OK, alternator output is way too high, let's see about how it is regulated. Well, it was regulated thru the ECU, meaning I had to replace the ECU to fix the problem.
And the problem never came back.
Oddly, no light bulbs ever burned out and the battery never boiled over, but that alternator was sure being over worked

Keep us posted please

Please explain more detail on "2 evaporator lines" and belt chirp on engagement.
Vee belt will always relax about 20 pounds after 1 hour running.
Are grooves available for dual matched belts?
CAT has machines with slugging which use an accumulator with a txv.
Is the belt wrap at least 90 degrees around clutch and C/S?
hotrodac

The new Delphi compressor might or might not have come from the factory with the correct oil for the system. Instead of pouring the same oil back in, I would have suggested installing fresh PAG oil from a sealed container, just to be on the safe side. Lacking the system specs, I would guess that the amount you added, 220 ml (7.4 fluid ounces), seems about right. I can only guess whether the oil has any bearing on the problem. Even though they're new, either the compressor or control valve might also be defective, or it could be something else as other members have already suggested.

Good Evening All,
Tbirdtbird - a good point however the Air belt only goes to the Compressor, Crank and Idler. I appreciate where you're coming from though. Once a few years ago I went to a service call on a Komatsu Crawler that wouldnt start. Checked power on key to starter solenoid and nothing. Checked back to the starter slave solenoid and nothing. I got so caught up in the fact I had no circuit from the key to the Start circuit that I didn't take notice of the fact that the hourmeter was still running even with the key off. I got my hands on some service info and found that the Start circuit went via the ECU, which wouldnt allow it to crank if the "engine was running", I busted out the osciloscope and found about 8VDC, as opposed to a PWM 12V Squarewave coming off the Alternator W terminal when the key was off...refered back to the info and the Tacho terminal ran directly to ECM and ECM relayed back out to the Hourmeter and Instruments. So an Alternator electronic fault was false telling the ECM that the motor was running and therefore wouldn't allow it to Crank. That was a valuable lesson during my apprenticeship...sometimes you have to look outside the problem.

Ice-in-tropics - No this setup is for a Single A section belt only. Belt wrap is good, Its pretty much a perfect equalateral triangle pattern, so its in contact with about 2/3 of the circumfrance of the pulleys. The belt chirp only happened after about an hour of run time which I put down to the belt bedding in as you mentioned. After a slight nip up it ran fine for a few hours with no chirp at all. What I meant by the two evaporator lines was connecting my themocouples to the two evaporator lines on the evaporator side of the txv to approximate if I had a full evaporator at the time of the problem occuring (if I could catch it, which I didnt). Turns out I didnt have enough room in there under the belly plate anyway to hook up as I had intended to and I sure as hell wasn't going to be removing the seat and hydraulic controls (again) to get access to heater box and test at the pipes further back in the cabin. I did however verify that the Compressor was in fact destroking as normal without having the Thermocouples hooked up, just by monitoring the gauge pressures after extended runtime.

I am not going to lie my CAT experience is fairly limited and I have never seen a system with an accumulator and TXV. Every vehicle I can think of off the top of my head here in Aus that has an Accumulator is a FOT system...Transit Vans, Ford Falcons, Early Commodores, some Saabs, 90s era Jeeps. Actually thinking of 90s era Jeeps, @Tbirdtbird I remember once many many years ago diagnosing a belt noise on one of those and whatever model that was had a fully ECM controlled Alternator and the driver circuit in that had gone bad and was driving the Alt flat out and loading the hell out of the belttrain. *I think* we ended up fitting a standalone external regulator unit to drive it if memory serves me right.
I digress, if the CATS have Accumulators they must have awful oversized TXVs for the cabin size or are running rooftop setups and safegaurding against slugging on low ambient conditions methinks.

Lastly - JohnHere - I should have worded that a bit better. I drained the oil that came with the Compressor, referenced the service label on the side of the unit that had the oil capacity and viscousity spec, and added the spec 220mL of whatever the grade was, I think it was ISO46 to the sump. I did sort of "flush" it for want of a better term with about 50mL of oil twice before the final fill..ie drained the shipping oil, filled 50ml, inverted the compressor, turned it end over end a few times, wound over 20 or so times by hand, drained that 50ml, repeat another time, then drain and do the final fill with 220mL.

At any rate, this machine is a headache and I would say that its the 3rd? Vehicle that I have come up stumped by in the last 12 or so years. My spare parts people have some ex techicians on staff (Shop used to be a fitting agent back in the day, look them up if you feel like abit of history, they're a bit of a big deal here, Highgate Industries in Adelade) who I have tried getting on the phone to but havn't got onto the guy I want yet. I spoke to one of the younger blokes there yesterday and he suggested that perhaps the suction line is washing off enough heat over its long run that it is condensing or starting to condense in the line. Which I immediately dismissed but honestly as improbable as that sounds at this stage I don't have any better ideas. I mean if it was having a change of state in the hose I would imagine I would notice a temprature change, not that I have very good access to the hose considering its routing through the machine. I never considered throwing a termocouple on the suction line at the compressor to check how cold it is, but I also never noticed condensation on the line either. I would also imagine that if this was the case given that the HS/LS ports are about 15cm away from the compressor, that my LS pressure would be doing funny things.

Another suggestion they had was if I had a delaminated hose. Once again I dismissed that as delaminated hoses don't delaminate then come good, then fail again. The only time I remember dealing with a delaminated suction hose it pulled the liner all the way down into the suction port of the compressor and made a hell of a mess - Like I knew there was an issue straightway saw it in my pressures and the noise from the Compressor.

Anyway I have veered off topic here a bit. It's good being able to discuss this here. I don't have any peers locally that do A/C other than what I would call Gas Jockeys, you know the type. "Just needs a regas" and when that doesn't work "Must have a leak" type repairers, who are no good to discuss this sort of thing with.

Your replies and insight are appreciated and I will update you all when I get back to the machine over the weekend.
Regards,
OP.

Initial engagement of roof top or sluggers often engage clutch during all startups w/ or w/o AC on, so liquid is gradually dissipated.
Belt chirp due to slugging:
Slugging can have sequential stages bang/bang/bang
1) liquid inside the compressor
2) suction line dips
3) liquid inside evaporator
The compressor inlet is not frosted or heavy condensation therefore the following is probably not applicable:
You have variable comp with txv?? TXV with V5 needs to be special with cross charge to reduce "hunting". If a normal txv is used it fights the variable displacement for refrigerant flow control. Result can be wide 25 degree swings in louver air and spurts of liquid exiting evaporator.
OT/accumulator systems are common with V5 but a missing OT will slug out of accum.
hotrodac

Not sure this is gonna help, but have worked on a low temp (-10F to -40F) freezer box and it had a non-variable Tecumseh comp, a TXV, and an accumulator and you could tell from the random frost line that the accum was doing its job. I see nothing wrong with having an accum in any system...

The classic approach to a troubled system is to recover, evacuate, and charge to correct level.
It worked before, something has changed.

Have to wonder how critical the charge is.

It would be a good idea to have the exact A/C specs for this excavator on hand. In searching for the machine's service manual online, I noticed that several vendors have them available for as little as $20 U.S. Money well spent, I think.

It does sound to me like the compressor is "slugging" every now and then, which might be causing the drive belt to come off. As suggested earlier, check the routing of the suction hose for any dips and bends where liquid refrigerant and/or oil could accumulate and be drawn back suddenly and intermittently into the compressor's low side.