A/C Noise As The Compressor Kicks Off

[chim]

On the l4240 there's a noise when the A/C compressor kicks off. First of all, the cooling functions just like normal. When I mowed today (hot & sunny) it cooled the cab sufficiently with the fan on medium speed. I noticed the noise today when I was out of the cab with the engine idling and A/C running.

I popped the hood and watched the compressor pulley with the tractor idling and A/C turned on. There was some belt squeal when the compressor shuts off. No noise when it kicks back on. Although I noticed the noise at idle, it remains as the engine speed is increased as well.

When the clutch disengages, it appears to chatter - sort of like it goes into machine gun mode. You can see the clutch rapidly engaging and disengaging for a second or so as its coil de-energizes. The rapid start/stop looks like it's causing the belt to slip. Belt is in great condition and the tension is good. I haven't checked the charge, but doubt it's causing the problem.

Any thoughts?

 

[DustyRusty]

The clutch on the compressor might not be adjusted correctly. I don't know what the air gap is specified for that compressor. Check the service manual to see what the gap should be, and check it with good old ignition point feeler gauge. My guess a minimum of .040.

 

[Dave_eng]

Here is the troubleshooting section of the WSM dealing with the AC.

I have attached the important pages from the WSM.

I would be looking for loose parts or worn bearings.

I do not know if the clutch assembly can be removed without the compressor but it may be more obvious in the field.

Dave

 

[chim]

Thank you both for the quick responses. I hope to check into it tomorrow evening. I'll post any progress.

 

[chim]

Finally had some time to check into the problem. The air gap was just out of spec on the wide side. It measures nearly 0. 020", and the spec range is 0.0079 - 0.017". I didn't modify the shim because a little cleaning has it functioning well. It's simple enough to get to the shim if it becomes a problem.

There were two things that I did find and work on. The first was simply cleaning out the dusty debris in the clutch mechanism. It looked like an accumulation of dusty vegetable matter just as you'd see in nooks and crannies of the tractor.

The second thing was a little bit of scratching on the face of the moveable part of the clutch. I gently worked that off with some 600 grit WOD paper on a smooth flat piece of metal.

Everything worked fine after reassembly. Thank you!

 

[DustyRusty]

Suggest that you take this up with your dealer, even if it is out of warranty. It had to have left the factory with this setting being incorrect. I would say that if you have a good relationship with the dealership, they might be able to get Kubota to pay for the repair.

 

[whitetiger]

Suggest that you take this up with your dealer, even if it is out of warranty. It had to have left the factory with this setting being incorrect. I would say that if you have a good relationship with the dealership, they might be able to get Kubota to pay for the repair.

The last L4240 was built at least 8 years ago so a couple of thousandths off of the compressor clutch face is normal. Asking any manufacture for warranty to clean and adjust a wear item on an 8+-year-old tractor would have very little to no traction.

 

[DustyRusty]

The last L4240 was built at least 8 years ago so a couple of thousandths off of the compressor clutch face is normal. Asking any manufacture for warranty to clean and adjust a wear item on an 8+-year-old tractor would have very little to no traction.

I am not familiar with model numbers, and I thought this was a relatively new tractor. You are correct, the manufacturer will not do anything for him.

 

[BruceP]

You did just what I would have in this situation. Take apart what you can, clean everything and touch up the metal clutch side with fine paper. (I would have done this on sheet of glass with wet paper followed with thorough rinse.... but that is just me )

One thing:

There was some belt squeal when the compressor shuts off.

This does not sound correct to me. As the clutch ENGAGES, the belt is loaded and may squeel a bit as the compressor comes up to speed. Thinking of it like this, it makes more sense that you heard the noise as the clutch was engaging with all that debris in it.

 

[chim]

You did just what I would have in this situation. Take apart what you can, clean everything and touch up the metal clutch side with fine paper. (I would have done this on sheet of glass with wet paper followed with thorough rinse.... but that is just me )

One thing:



This does not sound correct to me. As the clutch ENGAGES, the belt is loaded and may squeel a bit as the compressor comes up to speed. Thinking of it like this, it makes more sense that you heard the noise as the clutch was engaging with all that debris in it.

Celebration may have been a bit premature. It behaved in a similar manner when idling. With the engine speed above idle, it didn't seem to make the noise. I may try one more cleaning, resurfacing and adjustment.

The noise definitely happens as the compressor disengages. When it clicks into engagement, there's no squeal. When it disengages it re-engages / disengages / re-engages a number of times. Almost as though the spring is weak of it's getting hung up.

If another DIY session doesn't resolve it, I'll pursue a new clutch assembly. Kubota is awful proud of theirs.

 

[chim]

Update - I did some more cleaning up of the clutch and got it well within spec. The problem continues, but we may be onto something. A bud of mine with years in the HVAC trade believes the expansion valve is the main issue.

Apparently what I thought was clutch chatter while disengaging was actually the compressor attempting to deal with a pressure spike in the HI side just as it cut off.

He said he wants to try a new expansion valve, and replace the filter/drier before replacing the compressor.
Anyone know if there's a sticker on the tractor somewhere that indicates the amount of R134A needed after he pumps it down?

Thanks you

 

[eserv]

Update - I did some more cleaning up of the clutch and got it well within spec. The problem continues, but we may be onto something. A bud of mine with years in the HVAC trade believes the expansion valve is the main issue.

Apparently what I thought was clutch chatter while disengaging was actually the compressor attempting to deal with a pressure spike in the HI side just as it cut off.

He said he wants to try a new expansion valve, and replace the filter/drier before replacing the compressor.
Anyone know if there's a sticker on the tractor somewhere that indicates the amount of R134A needed after he pumps it down?

Thanks you

Well he should be evacuating it and then putting the same refrigerant back in!

 

[chim]

Well he should be evacuating it and then putting the same refrigerant back in!

I agree, but I'm not certain it has the exact right charge now. It works, but it could be a little high or low on charge.

 

[DustyRusty]

On the receiver drier, there is a sight glass, and you fill it till the bubbles in the sight glass go away, and then stop. Check your Hi and Low gauges, and add whatever additional you need till you have the correct pressures. He should put his gauges on it prior to evacuating the system. If it has an overcharge, bleeding off some refrigerant might do the trick without any further work. The inexperienced add refrigerant thinking that will improve cooling when poor cooling is the result of something else. If you don't know the history of the machine, this might be the problem from before you bought the machine.

 

[chim]

Known history of this tractor - bought it used in December of 2018. Used the A/C for 2-1/2 Summers and at times in Winter to clear condensation in the cab. No refrigerant was added while I owed it. Always blew cold. Pic of thermometer stuck into vent is from August of 2019. The screechy belt racket started recently.

When the $70 worth of stuff and my bud show up we'll see if that does the trick. Probably toward the end of next week. I'll post the results.

 

[DustyRusty]

If he uses a recovery machine, he can weigh the recovery bottle before and after to establish how much refrigerant is in the system. If he is opening the system, you should also check the oil in the compressor and if it is visually compromised, flush the lines and put all new oil into the system. My experience with expansion valves is they are either good or bad, not intermittently bad.

 

[chim]

Update - Replaced expansion valve and filter dryer and we're back in business.