Bummer - I think my AC Compressor is Failing!? (M7060)

[Russell King]

You might want to see if the clutch is receiving a steady voltage signal or if it cuts off and on.

 

[jaxs]

You are on the cusp so waiting until it's warmer sounds like a good idea. If the short cycling continues simply disconnect and jumper low pressure switch and/or clutch control wire to see if cycling is caused by clutch or controls. Odds are on the control circuit-stat or bulb mounting.

 

[Old Machinist]

Your observation on the low pressure switch specs are interesting.

An inline tap to monitor voltage on the clutch would be a good idea.

When mine does it it appears the compressor is locking up and causing the clutch to slip. I guess low voltage would cause the same effect.

 

[psdstu]

OK, more fun tonight! Charged the system. No issues there, as I've done so before on other R134A systems.

AMBIENT TEMPS WERE AROUND 65F TONIGHT WHILE DOING THIS TESTING AND FILMING FYI!

Still having odd behavior post-charge:

- When AC system is set to "OFF" with the engine running, the compressor clutch is still. Zero rotation. High and Low sides settle to equal pressure as expected.
- When AC system is then turned "ON", the compressor clutch engages, AC operates as expected and blows ice-cold. Low and high pressure ratings are in the range of "normal" for a charged R134A system. But, after about 30 seconds, the compressor clutch disengages and the system starts to continuously short cycle. It basically seems to engage the clutch for 30 seconds initially, then disengages and re-engages and enters into this 5ish seconds engaged / 3 seconds disengaged loop.
- That initial disengagement after about 30 seconds of run time doesn't seem to be associated with a low-pressure min or high-pressure max trip - as you can see in the video below at approx 1m:00s, the compressor clutch drops while the low side is around 30psi and the high around 150psi. Those are normal readings for R134A system at 65F ambient temp.
- When the system disengages the compressor clutch with the AC 'ON", the clutch drags a little bit. That's the slow herky-jerky action you're seeing in the video. As mentioned in the first bullet here, there is zero rotation of the compressor when the AC is set to "OFF"

So I'm thinking it definitely was low on refrigerant (which we all already knew from the previous gauge readings...) but there seems to be a problem with the compressor clutch or the control system for triggering it. Does that seem right, and any guesses on what to look at next?

One other note. The factory manual has what may be some incorrect info in it with respect to the low pressure side min pressure switch...it seems to indicate less than 28psi will trip the low pressure switch, yet the factory low pressure normal range is 22-28psi? This seems odd?
View attachment 175968

Well that sure is confusing..... not sure how that can work. 22-28 psi normal..... low set point 28 psi????

 

[jaxs]

Well that sure is confusing..... not sure how that can work. 22-28 psi normal..... low set point 28 psi????

It's all about fun and games, don't worry about the mule,just load the wagon.

 

[GeoHorn]

It’s difficult to see your gauge (outer range)…. is that PSI..?

If so, the High side press is running 150…and is considerably low when the compressor is running. Add more refrigerant.

(How much have you installed so-far? Did you evacuate the system in the beginning..?? or did you simply start adding R134a ?)

 

[Donystoy]

The most important thing to do is to make certain that all coils are completely clean before trying to diagnose a problem as previously stated. This is with water on the condenser coil. Then operate the system with an ambient temperature of at least 75-80 degrees F. In normal operation the compressor should run steady until the cab is down to temperature after which it will cycle on and off to maintain temperature assuming it is controlled by suction pressure. I agree that if the tractor is overheating you have an issue with the engine rad or cooling fan.
You should never just add refrigerant to the system without first determining where the leak is and repairing it as you will otherwise be in the same situation after it leaks out again. It is critical in any refrigeration system that they have the correct amount of refrigerant as the compressor depends on a cold suction to help keep it keep from overheating. An overcharge can result in liquid slugging into the compressor which will damage or destroy it. We use to say in the industry that a compressor can compress liquid one second before it self-destructs. This is why it is always best to evacuate the system after re-claiming the refrigerant and repairing the leak. Then weigh in the proper amount.
Just guessing but maybe your original problem was a dirty condenser and engine rad and the refrigerant charge was correct and no leaks considering the cold ambient temperature. If that is the case you now are over-charged having added refrigerant.

 

[jaxs]

It’s difficult to see your gauge (outer range)…. is that PSI..?

If so, the High side press is running 150…and is considerably low when the compressor is running. Add more refrigerant.

(How much have you installed so-far? Did you evacuate the system in the beginning..?? or did you simply start adding R134a ?)

It's important to know why something is being done. Aside to possibly weighing charge,why should system in this case be evacuated?

 

[GeoHorn]

It's important to know why something is being done. Aside to possibly weighing charge,why should system in this case be evacuated?

I only wanted to know in order to assess is answer to the question as to how much he has added.

So many times in forums such as these… not all the necessary information is shared… the participant will tell only part of the story not knowing they’ve left out important info.

 

[jjb01016]

OK - mostly good news over here. We had some warmer daytime temps with sun yesterday ~75-80F, and I ran the tractor for a bit. I got it good and heat soaked, then stopped and turned on the AC to max, RPMS to 1500 and hooked up the gauges. I had added 12oz of R134A (one single can...) and did have to evacuate a little bit out of the system, it was slightly overcharged. I was getting high side pressures of about 270-80psi which is high for the ambient temperature. But I noticed right away that the compressor wasn't cycling like in the previous video I posted, which was at night with ambient temps only around 60F.

After evacuating a bit more refrigerant, I had a steady running system at ~28PSI low side / 240PSI high side. No compressor cycling. AC was ice cold and consistent for a good 1.5hours or so after that while mowing.



So I guess the lesson here is the obvious one - start with verifying refrigerant levels, and troubleshoot your system in appropriate warm conditions.

Going back to the overheating I noted that happened concurrent to the AC starting to blow warm...I'm wondering if all the cycling of the compressor was causing it to start to lock up, which was also in turn stopping the radiator fan from spinning since they're both on the same belt.

If I have time I'll follow up with some multimeter work to the make sure the compressor clutch is getting the appropriate inputs, and do some sniffing with my leak detector. But for now, I'm just happy to have functioning AC again!

 

[Shawn T. W]

The radiator cooling fan should run wether the ac compressor is running or not, if the clutch was frozen
.. it probably would still be frozen, which doesn't sound like ...

If you ran it for 1.5 hours mowing, I'd say it's running fine now, just needed a boost of freon, but that leads to the question of why? It must have leaked out somewhere ...

I had an old pickup truck that had a very slow leak, every spring it needed a 12oz can, worked fine all summer, then by the next spring it needed another can ... I could live with that ...