Jd AC No Work Sometime

[LVH09312013]

My Jd 3720 W/Cab Ac would not work at all and just recently the last week worked great.

Here's what I checked( All screens etc have been cleaned periodically). Thought the clutch was not engaging so to verify I disconnected the ac clutch from its power supply. With tractor running jumped from the battery to the ac voltage lead & it ran fine. Checked the lead in cable for voltage and there is 12 volts but when connected to the ac clutch lead it did no engage. This is really weird as the connectors are OK. anyone have a solution to this?

 

[Tx Jim]

Welcome to TBN
Has AC refrigerant pressures been checked with gauges? Possible faulty high pressure or temp switch.

 

[LVH09312013]

Hello Jim;

Yes the refrigerant was checked and is OK. Still but I do get the 12 volts to activate the clutch. Given so will the pressure or temp sw still cause the problem although the voltage is at the clutch? And do you know where those switches are on the JD3720? This site is great and JD wants upwards of $200.00 for a tech manual I think that's gross.

i also located the relays behind the control module there are 4 of them I'm sure one of them must control the compressor as well. Your thoughts?

 

[RPW]

A faulty hi/low pressure switch will cause the clutch to not engage. It is on the negative side of your clutch plug. In other words your clutch is grounded though the switch. Easy way to check is to disconnect the switch and jumper the two pins.

 

[pmsmechanic]

What is the air gap on the electric clutch on the A/C compressor. Each switch adds a bit of resistance to the circuit and by the time it gets to the clutch there isn't enough voltage to apply the clutch. I've had to reduce the air gap on some tractors just to get the A/C clutch to engage. Sometimes the volt meter will show adequate voltage without a load applied but when the load is applied it is considerably less. Try checking volts at the same connector with the clutch hooked up and see if the volts are close to the same. If not start checking your connections and switches. Just leave everything hooked up and check voltages before and after each switch etc.

 

[JDneophyte]

Exact same problem we had on our 3720 , 3 years ago. Went through every possible iteration of what could be wrong, no issues.....and still blew warm air. John Deere sent a technician out, $760.00 later after checking everything I checked (and I replaced the expansion valve in the roof, that was a bear).....he removed the hydraulic fluid radiator (which is in front of the condensor, the small one), power washed the newly exposed area.......Shazam, cool air in cab!

I went through exactly what your going through........and was VERY surprised that this was the cause. Every time our air conditioner fails, I pull the little radiator off, power wash......and it works perfectly again.

The system is a piss poor design......not enough air flow over condenser, and it's useless (the "fish bowl" gets hot!). John Deere had a great idea, just didn't test it in real world conditions enough to see this problem (when cutting grass, dusty conditions).

P.s. If your a/c clutch is working correctly, you'll see a slight drop in RPM.