Cat 289D, No AC

Cab was getting warm the other day, so I turned on the AC for the first time this season and it blew warm air. Compressor clutch is not engaging. I replaced the fuse, swapped out the relay with another, still no AC. Where should I look next? I disconnected the pressure switches and reconnected also. I also powered the compressor clutch directly from the battery and it engaged.
Serial # TAW01821

probably need to check pressures. most systems have a low pressure cutoff switch to keep the compressor from engaging when the freon charge is too low...

Put a gauge set on it. Static pressure on A/C at room temperature is approximately 70 PSI. We've found that most Cat gear doesn't hold an A/C charge well over our -35 winters to begin with. Usually if a hose is going to leak on those skid steers its usually the 2 that go to the condensor on the rear door. All that flexing from opening the door eventually damages the hose. Only way to find a leak on A/C is to look for the oil seeping out or to have the remaining refrigerant (if any) removed and the system pressure tested with nitrogen. I would recommend leaving that to a pro though.

Ayep, as the hoses get older, they need that oil circulating around to keep things sealed, seems the rubber is gas permeable to the refrigerant without the oil. Wouldn't be bad to spin the compressors for a bit every week to keep the oil moving and everything sealed.

With the system off you can put a volt meter on the low side switch, it should be closed, if its open its likely out of juice. Careful on 'dumping a can' in there as equipment systems are tiny compared to cars / trucks and you can overcharge it and jam up the compressor with too much pressure. A can with a gauge should work, high idle and put a thermometer into your outlet vents, add a little squirt and watch the temps. System will be the coldest just shy of full charge.

Thanks, I will check it out. The machine is not even 3 years old with around 300 hours on it. It barely got below 0 here this winter, but makes sense after sitting most of the winter. I did use it for some snow blowing over the winter, so it did get used.

usually to the low side plug you'll see 12v on one side and the compressor on the other with everything in running shape, if the pressure is good and the switch is open, could be a bad switch, usually they're pretty cheap.

It is supposed to rain here on Friday so I will bring the machine back to the shop and check it out using your suggestions. I will let you know what I find out. 38 here this AM, so I will not need the AC this morning!

I brought the machine back to the shop and replaced both pressure sensors, still no AC so I am leaning toward a leak and no pressure in the system. I inspected the hoses running to the condensor an the door and did not see any oil staining due to a leak. I have a set of gauges along with a leak detector on order and should be here this week. I take it that the connections where the pressure switches screw on are where the system gets serviced. I am assuming that this is a R 134A system, the connections are not typical of this. How many lbs of freon does this system take?

No, the system should have seperate low and high pressure ports. On the 289D I believe they are located at the rear of the compressor. I believe it takes 2.2lbs of R134a to charge the system as well.

92U 3406 said:

No, the system should have seperate low and high pressure ports. On the 289D I believe they are located at the rear of the compressor. I believe it takes 2.2lbs of R134a to charge the system as well.

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Kinda of hard to see the back of the compressor, but I shoved my phone in there and took a few pictures. There appears to be a bunch of bolt heads showing, but no quick connect fittings. I will bring a mirror and a flash light today and see if I can get a better view. Thanks for the response. 32 here this morning!

If not there, they might be located on the bottom of the cab, left side. Might have to lift the cab to see them.

Just went through this same deal. You can jump the high and low switches to see if the compressor will engage. Mine ended up being so low on freon the low pressure was holding it out. Pulled a vacuum on system, added freon and compressor engaged at about half a can. These systems are small and need the right amount of refrigerant. My Case holds 18oz might be good idea to see what yours calls for. Good luck

Finding the fill ports, so, there's one on each side of the compressor, the high side is usually between the compressor and the radiator (condenser) will usually have a plastic cap and its a small quick disconnect fitting, 10mm or so, The low side (fill) is between the cab and the compressor, slightly larger qd fitting. Sometimes they're tucked under or inside the cab or right on the compressor itself. Looks like 2.2 pounds (weight) is the magic fill number from empty.

If you changed the fuse and relay was the fuse blown? If so I would start at the compressor first before checking pressures or looking for leaks. Put a DVOM on the ele connector to the compressor and see if the coil is shorted out. It has been a common problem with the compressors lately for the Eletromagnetic coil to go bad.

I wired the compressor clutch directly to the battery and it engaged. I did replace switches and swapped relays, no help. I am leaning toward no pressure in the system. I will truck it back to the shop again this weekend and lift the cab to find the fill ports and check the pressure. If low I will evacuate the system and recharge it. Fuse was not blown, first thing I checked.

install your gauge set and check static pressure. With the machine not running and and with a 70* ambient temperature the high and low gauges should both read equal pressure of around 70psi. That will verify a pressure issue. I think that machine also uses what is called a dely timer which prevents the compressor from getting power for about 30 seconds after machine start up. You can check it by testing power with a DVOM at compressor plug. Switch on, A/C on, minimum of 9.5v should be supplied to compressor in 30 seconds.

Dragged the machine back to the shop yesterday, but did not have time to work on it till this afternoon since I wanted to get outside stuff done yesterday before the rain y and had an errand to run in VT this morning. I guess the NH DOT pulls the plow gear off their trucks once May rolls around since I was driving on snow covered I-89 this morning without and orange truck in sight! Makes you wonder why am I fixing the AC system yet I am still burning wood!
I lifted the cab and did find the ports on the HVAC unit. I hooked my new gauges up and had zero pressure, so I must have a leak. Hooked up the vacuum pump and pulled a 29 on the gauge for a few minutes. I removed the vacuum pump and added some R 132a to the system. I also bought an electronic leak detector and took the advice that the hoses on the rear door develop leaks due to flexing. Sniffed around those and it started beeping like crazy. It was around the clamp in the center of the condenser. I will replace both hoses and then recharge the system. If I evacuate the system do I have to add more compressor oil or only if I flush the system? How many oz. if I do?
Thanks for all the advice. Since I own 12 AC systems I chose to spend the money on the tools to fix it myself. Last year I had a mouse chew the wiring harness on the HVAC system in my 305C CR excavator and had to pull that out and split the case to re wire it. I will evacuate that system next and re charge it also.

Adding oil is kind of a crap shoot. If it has the common Sanden compressor used on trucks and equipment they have a dip stick on the compressor. You can find a manual on the internet that tells you how to check the oil level in the compressor, then you have to guess how much oil to add to the hoses to account for the amount out circulating in the system. 2 oz usually comes to mind.

I recently took an F250 to a mechanic for a bunch of work I did not have time nor desire to do. One thing was the AC compressor was locked up. He said there was very little oil in the system. It had been a slow leaker in the past and I would add a little refrigerant here and there to keep it going. Then when something let go I replaced some hoses and parts. I remember good and well adding the specified amount of oil for the work I had done back then. Where it went I don't know but maybe there was so little oil in the rest of the system I should have added more.

Oil adding is always a question! if there is oil all around that leaking hose, you might want to add half an ounce. If it was a slow leak and just vented out the gas, you most likely did not loose any oil, if you change parts, sometimes they will have a guide to how much to add.

I just keep track of how much oil comes out when I perform the recovery and just add that much back in, maybe add an extra half ounce to an ounce if it puked a bunch out through a blown line.