I have a trailer house furnace and the thermocouple apparently is
going bad because the pilot goes out once every week or two. It just
started doing that this fall, after the pilot was off all summer.
I was at a local building supply and saw they sell a packaged
thermocouple, but it does not specify what its for. Are all
thermocouples created equal? I mean, can they be used for ANY
furnace, or water heater, or any gas appliance? I am hoping so,
because I dont know where I'd get one specific to this older Miller
(mobile home) furnace.

PS. If I could figure out how, I'd convert it to electronic ignition,
but that seems like a big job.

Thanks

This is Turtle.

i will use the words of what type thermocouples are loosely to say the
least. ALL per say 24 volt thermocouples will work in all applications
just fine. Now there is a difference in the types of thermocouples that
you may buy on at stores 7 wearhouses today. all will work but some are
made to last longer and some is made to put out just a little more mill
Volts for the gas valve to hold it open.

The HVAC type is made to put out about 27 to 29 Mill-volts and then the
Hot water tank type is made to put out 24 to 27 Mill-volts service.
anything 24 volts or over will work fine but the higher volt
thermocouples seem to last longer.

TURTLE

No, all thermocouples are not the same, there are many different types,
J,K,T,R,S, and so one. The difference is the materials used for the
wires. There must be 2 dissimilar metals for the junction to produce a
voltage. Some use iron/constintan, others use copper/ cupronickel,
others use different metals. They have different outputs at the same
temperatures and are not interchangeable. Most Tc's for home use will
be either J or K, and of those most should be J. You can tell by the
wire insulation colors. J is red and white, K is red and yellow. Red
is negative. As long as your wire color on the old one matches the new
one it will be ok.

Also, the millivolts is not what opens and closes the gas valve, that
is just the signal to the temp controller telling it whether or not to
open the valve. There is no voltage applied to a TC, so the notion
that a TC is 24 volts or any other volts is wrong. The TC is an output
device, not an input. The temp at the junction produces the millivolt
signal.