Furnace - Not heating enough - Faulty Thermostat.


Old 10-20-04, 08:14 AM
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Furnace - Not heating enough - Faulty Thermostat.

I own an Old house with and Old furnace/Burner. (can't tell you the model nor the make .. its that old).
I never had to mess with the Pilot or anything, we simply messed with the thermostat.
This year it would not turn on, so we got PSE&G to come and turn it on for us. They said this furnace was hard to turn on and only someone with experience could have done it (I was not home when he came - he told this to my wife).
Anyways, the furnace fired up, but now it does not stay on long enough to heat the entire house. It only fires up for a little while when it gets to about 60 degrees it will shut-off.
Do I have a faulty TS? or is it a bigger problem?
Can I replace the TS without fear of screwing things up even more?
What dangers are there, if I replace the TS myself?

I am not a handy person in the least bit, and I don't feel too comfortable doing it. But at the same time I don't want to pay someone to come and plug a couple of wires (if it is that simple).

Great site you guys have here, I will most likely visit here often.
Thanks for your responses in advance.
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Old 10-20-04, 11:32 AM
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Ok here is an update on the situation.
I have, since I posted, gone to Depot. I bought a Honeywell heat only TS.
The guy told me, to simply put the two wires together and see if the Furnace "goes off or turns on".
Well, I did that, and did it turn on? Yes & No. It did not immediately turn on.
I put the wires together (left them together) and ran to the basement. And it was not on, there were no sparks either. I fiddle around with the little box on top of the furnace and a few seconds later it turned on.

Now why would it not turn on right away?
Is it really a thermostat problem?
I am letting it run for a while, (direct connect) to see if it will continue heating, at least until the house gets warmed up.

N.E. comments or suggestion will be greatly appreciated.
Old 10-20-04, 12:01 PM
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Have to know what you have there. Open the blower door and see if there is a wire schematic there . It should have the make and model. Last year was the pilot on all the time or not? We need more info.

Old 10-20-04, 12:03 PM
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Hello: orejon99

May or may not be a problem with the delayed turn on. Some older units have a built in delay. A warp switch inside the old style gas control valves. Some can take up to two minutes to fire up between the time T-Stat is turned up or turned on or does so automatically because room temp drops below setting temp.

Does not matter. Once heat is called for a delay will result with a delayed action gas control valve. As long as furnace turns on by itself when heat is called for, control may be a delayed action gas valve. Usually a marking in words to identify such on the control but may or may not be. May have faded over the yrs or covered with dust, etc.

May or may not be a bad wire connection at any wire terminal where you "fiddle around with the little box on top of the furnace and a few seconds later it turned on."

Little box may be the location where the T-Couple (TC) or Pilot Generator (PG) connects into. A weak TC or PG can also cause a delayed fire up or no firing up of the burners at all. In either case (depending upon the safety device used) the pilot flame may or may not stay lighted.

Cleaning a PG may help but usually not. Replacement is the only option. PG has two wire leads from it and a TC has a threaded end hex nut. Weak TC must be replaced. Cleaning does nothing. Replacement is the only solution.
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