Elimating a themastat help
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naturalgas
Well-known member
Jump RH and W together if it runs fine it’s the thermostat. I doubt it though.After looking at pic it doesn’t matter which R use jump together with W . RC and RH are already jumped. Better to take both RH And W off thermostat and twist them together if heat keeps running fine, it’s a bad thermostat. If not you have elsewhere to look. Could be a dirty flame sensor or if you pull air for combustion from outside you sucked in a leaf and it’s affecting pressure switch.
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D45
Well-known member
Not to steal, but why do tstats go bad........or whats the lifespan on these?
It seems like my furnace is running more often, than it did last year........and the tstat seems to not be hold the proper temp
It seems like my furnace is running more often, than it did last year........and the tstat seems to not be hold the proper temp
BillK
Well-known member
End,
That is what mine does right before the hot surface ignitor burns out. There should be a view port in the furnace that you can look in and see if the ignitor is glowing properly.
This is assuming that it is a modern furnace with electronic ignition, not an old standing pilot type.
I keep an extra ignitor on hand. Have had to change it about three times in 14 years or so. Takes about 5 minutes to change.
That is what mine does right before the hot surface ignitor burns out. There should be a view port in the furnace that you can look in and see if the ignitor is glowing properly.
This is assuming that it is a modern furnace with electronic ignition, not an old standing pilot type.
I keep an extra ignitor on hand. Have had to change it about three times in 14 years or so. Takes about 5 minutes to change.
naturalgas
Well-known member
naturalgas
Well-known member
G is ground. TT at the heater eliminates thermostat and wiring up to tstat.
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you know those are just relay contacts...
if the OP wants to test the thermostats. All he have to do is turn up the heat and check for 24Vac between W and C.
naturalgas
Well-known member
I would think if he knew how to use a volt meter he would know what wires bring on the heat cycle.
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bobbyjean
Well-known member
Like most things today. They are put together in sweat shops in China or whatever 3rd world co. Is low bidder. The old mercury tstats last forever.
the old mercury tstats do last forever....just clean the dust bunny's off the bulbs and they even stay calibrated...
to eliminate any guess on either stat or wire run ....you could go to unit low voltage terminal board(if it has one) and jump out r to w..that way you can make your checks as it runs...
Falcon67
Well-known member
Something else to consider - gas heaters, least ones we've had, use a temp switch in the firebox to trigger the blower after call for heat and the fire box reaches a low set point. If cold air leaks into the return plenum somewhere (like our old house, came up through the floor boards) it can cool the firebox and cause the blower to switch off while the heat call is still on and gas still pouring the coals to the fire. It may have run enough to raise the temp near the t-stat which then kills the burners but about that time the fan kicks on again. Can drive you nuts trying to find the right setting. Some of the replacement switches seem to be really sensitive.
48RON54
Well-known member
Plenty of videos on Youtube showing how to jumper out/trouble shoot your thermostat but given the description of what is going on it sounds kinda unlikely. But, its easy to do and will either eliminate the t-stat as the problem or cofirm it is the problem. Might as well start there. What is 10 minutes of your time? T-stats are relatively cheap part to replace.