New Holland TM140 Tractor A/C

Hi all, new to the site. I am having trouble with the above tractor.If anybody has any experience I would be very grateful. My problem is intermittent. Ac works fine some days and others it doesn't. At the moment it's not working at all. Refrigerant charge is correct. Pressure switch near compressor is made. Pressure switch on roof is made. Thermostat has four wires all of which have 12v in them. The power at the pressure switch near the compressor is not there at the moment. This is the problem. I cannot not see a dedicated fuse or relay for ac system . Would anybody have a wireing diagram or know where the relay is so I can check it's operational. Also is there a secondary unit for the thermostat maybe that I am missing and is faulty. Any info or suggestions kindly appreciated. Regards Barry.

up in the roof you will find a ice stat on ns they are troublesoom

Thanks for your reply. If I'm not mistaken is the thermostat and ice stat the same thing. The bulb for thermostat is located in the evap coil. I have bridged out stat already. Will try tuning tempory wire from stat to pressure switch during week to check if wires have broken somewhere.

Would you know where relay for a/c is located ?

dirrerent pre 2001 same as after relay by drivers knee