hi guy's this is the thermocoupler i use one year I had to replace it two times is there something I'm missing here. its on a boiler that heat's the house.
Honeywell 36 In. Lead Length Universal Thermocoupler - Gas
You'll have to find an HVAC forum or ask the manuf. You also may need to run some voltage/current/resistance measurements but the elec. spec's on HVAC parts seems to be Top Secret.
If it puts out a weak signal try another new thermocouple (some are just bad from the factory). If BOTH seem to be putting out weak signals it's quite possible your gas valve is starting to fail.
In BC the thermocouple is allowed to keep the gas valve's pilot light on for up to 90 seconds after you blow the pilot out.
If I do a drop out test on a thermocouple and it can't keep the gas valve on longer then about 30 seconds I change it out. I like to see 50 seconds+ though.
Last edited by Thatguy; 11-28-2009 at 05:47 PM.
A thermocouple that gets too hot will fail, or more precisely will stop generating power to maintain the coil in an open position. IF the main burner flame is so large it is encompassing the thermocouple, or if the pilot light is not on the tip of the thermocouple, its operation will be erratic. Overheating and age are about the only two causes of thermocouple failure, and if yours are going bad that quickly age is probably not the cause.
Wouldn't the best thing be to call a service tech out to check the gas valve and thermocouple? They have the proper test equiment.