My pro mig 170 has decided to misbehave, initially the gas stayed running & the wire stayed live without pulling the trigger. I tested a few items with the multimeter and discovered that the finder relay 45/69 was stuck. I then discovered that this is a common fault and replacing the relay with a new 45/71 should do the trick. Having replaced the relay on the pcb, I now cannot get any life when pulling the trigger, the fan runs when I turn the machine on but when I pull the trigger nothing happens. If I short the relay contacts across it goes back to the gas on, live wire etc and if I then pull the trigg the wire spool runs? Any ideas as I'm getting desperate now Any info appreciated.