Quote Originally Posted by pauljones1976
Lexsmaz, you are correct in saying that your way will actually indicate power flowing through the thermofan positive wire. However, it will still light the LED even if the circuit is broken at the thermo (ie: if the thermo motor dies) and that method will steal current from the thermofan(s) circuit. This is the reason I suggested putting a relay in series with the power wire to the thermo. That way you don't affect the thermofan circuit currrent (although the relay coil will draw a small amount more current) AND it tells you if the thermo is actually running. If it's not running, the circuit will not have current and the relay will not energize thus not engaging the LED.

Cheers,
-Paul.
Putting the relay coil in series with the power wire to the thermo fans is not a very good idea. I don't think the relay coil will enjoy the thermo fans trying to pull 30A through it, it WILL burn out the relay coil . Also you add extra resistance and therefore voltage drop by wiring things in series.
Also a light hooked up in parallel with the thermo fans will not "steal current" from the fans. The pissy little amount of current the light draws will be supplied in excess of the current drawn by the fans (ie the whole circuit will draw the amount of current it needs to power the circuit).

I can't believe this thread has gone on so long for something that is so simple .