Can't seem to fix the a/c on new to me 1640. Had a leaking high pressure hose, replaced that, evacuated system, no leaks, started charging system and all at once the compressor clutch will kick out and low pressure light will come on in cab. Also the fan motor will quit and try to start then quit, etc.. Could it be the air conditioner relay in the cab? I have checked the ground and it seems to be ok. May need to say that we have 3 cans of 134 already in the system. If you shut the combine off and let it set for a while everything works until the low pressure light, clutch kicks out, and fan starts starting and stopping.