I have the THC300 and I am running Mach 2.I get the tip voltage read-out when I manualy fire the torch.The ark O.K. led comes on and the computer ark ok comes on.But when I try to fire the torch with an M3 command it does not fire ,if I click fire torch in Mach2 nothing happens.

My question is Do you think I do not have it configured correctly ,because I don't know where the pins are for torch on and torch off.

Without looking up the specs I think the Torch relay on the THC Sensor Card fires from port 2 pin 1. It uses Output1 (M03/M05) to fire the torch. You should see Output1 in MACH go active. Make sure it's setup in Ports & Pins to Port 2 pin 1.

Support for THC300, THC500 and MP1000-THC at CandCNCSupport yahoo groups.