So the AC in the tractor decided to stop working. Seemed to be just fine, had to run the heater due to a cold snap, switched back to AC the following day with no issues. Turned it off for a bit because it was too cold and when I turned it back on, no cold air. I did have the occasional belt squeal with the AC in the past, but otherwise, things worked. Tractor was bought used so I don't have the full history on it, but the AC wasn't blowing cold when I bought it (dealer said they fixed but actually just cleaned the coil and charged it).

So, knowing just enough about AC systems to sound semi-educated and probably know the names of parts if I want to start throwing money at it, I figured it's time to ask for help. Here's what I know.

AC clutch won't engage. First start up of the day, it will kick on and off a few times before giving up and not coming back on. If I unplug the harness and apply 12v to the ac wiring, the clutch engages and the AC blows ice cold air. Outside temps around 75, the low pressure side reads around 14 and high pressure around 175. Didn't seem to want to take much freon with the AC wired to 12volts. Wouldn't take anything with the factory plugs hooked back up and the clutch not engaged. I think I got most of a can of freon added and the pressure jumped from 14 to about 15. Pressure readings were taken with 12 volts applied to the ac system as it won't run or read proper pressures without the clutch engaged.

So, does this mean I have a restriction or a bad compressor? Orifice? Dryer? How to narrow things down without throwing money at it?

 

Make and model of tractor? It could have a bad high, or low pressure switch...

 

New Holland TD5050

 

That model uses both a low pressure switch, and a thermostatic switch. I would check there first.

If you have cooling and the pressure's look good (and they do...) when you put 12vdc to the clutch then the system is working. Most likely a bad switch.


Parts are available here, it's where I buy mine...

http://www.apairinc.com/shopping/?model=12223

 

The only switch under the hood is on the dryer. Your link says it's the Hi-Lo pressure switch and it's normally open. If I stick a meter on it, there's continuity across the two posts, so if it's a normally open switch, that could be the issue. (tested with the key off)

If there is a low pressure switch or thermostatic one, it's got to be up above the ceiling liner by the evaporator coil. Don't know if I can reach that by just pulling the radio and doing things one handed, or if the whole liner has to come down.

I guess I can just unplug the normally open switch and it should work for testing purposes? Too cold today to do to much with the AC, but will be back to 79 tomorrow so I can play with it then.

 

In my LS 180, the low pressure switch is on the dryer
the high pressure switch is by the compressor

STOP adding freon until you are sure your compressor is working, you can blow yourself up

Best bootleg way to test the low pressure switch, bypass it with a paper clip, the compressor will come on. charge or no charge

Use your guages, check your charge


My ls 180 had a bad relay in the power center, Ford uses the same one for thier A/C $20 cheaper

 

I only added the Freon because the pressure was down at 14 psi. Can't add any if the clutch isn't engaged. I tried for grins and giggles and it won't go, so I'm stuck at 15 psi.

The only switch I have between the compressor, coil, and the cab is the one on the dryer. Unplugging it makes no difference. Jumping the pins in the connector makes no difference. Clutch still won't engage. That means there's either a sensor or switch above the ceiling panel that is faulty, or something else is going on.

Parts diagrams from New Holland have been less than helpful. The only pressure switch I've seen there has been the one on the dryer, and it wasn't even called out as a part (supposed to replace the dryer too if you open it up).

I really don't want to pull the ceiling liner out of the tractor, but at the same time, the evaporator coil is probably dirty anyway.

Also found a place online that claims they sell the service manual in pdf form for the tractor, that should cover this. Debating on going that route first.

 

where are your relays?
Mine are on the back of the cab inside the engine compartment

I just started pulling them, and changing with a good relay, and CLICK the compressor came alive

Never hurts to have a service manual.....
I'm lucky, the parts guy where I go prints me what I need

 

My relays are in the same spot. The owners manual didn't list one for the AC, which kinda surprised me. Maybe I need to start pulling them and checking regardless of what the book says. There's not that many relays, so it should be easy enough to check.

 

Mine didn't either. It was right hand top one

 

Well it wasn't the relays. I swapped a new one in place of each relay one by one with no luck. I pulled, ohmed, and re-installed every single fuse, no luck.

I pulled the ac panel out of the roof liner and found the other switch on the line and checked it with a meter. It read closed on the meter. Unplugging the wires made no difference. Jumping the wires made no difference.

The AC off to max cold potentiometer switch has 4 wires and I wasn't sure how to check it as google says it should only have three wires, but playing around I did find wire combinations that showed variable or no ohms depending on switch position, so I'm guessing it means that works.

I also found the thermostatic switch, but have no idea how to test it. I paid the money for the manual download and it's about useless. It tells me to test these items, but doesn't tell me how to test. I know I need to test them. That's what I bought the manual for.

I'm not sure what to do next. I'm worried that if I just take it in, they won't know either and will just replace everything because they can't narrow it down.