have to ground a/c relay to get compressor to start

The ac compressor wont come on it is full of freon and the fuses are good and the relays are good too. I can get it to come on if i put ground to the a/c relay. All the fuses and relays are good the a/c system is new the only way I can get the compressor to come on is to put a ground to the relay in the juction box