I rebuilt my Empire DV-235-3SG wall heater last season with a new gas valve and burner assembly and it worked fine. This season, I cannot get it to work properly. Right now, the pilot lights but when I turn the knob to "on", the pilot goes out. Evidently the thermocouple is not sending the electric signal back to the valve to open the primary gas flow. I have tried heating the thermocouple with a meter on the cable end and see some activity but don't know enough about measurements to know if "some" is enough. It is an" all or nothing" thing or could the thermocouple be weak?