Question about Heating & Cooling
This furnance has been in the house since it was built. The only thing it's ever needed aside from normal maintenance, was the ignitor was replaced about eight years ago. We've been having rather odd weather for May this year, and I turned the furnace back on last night after it had been off for a couple of weeks. Got up this morning and the house was freezing and the furnace was blowing cold air. Turned it off at the thermostat and it still continued to blow cold air. I had to turn the power off to the furnace because the blower would not stop running. I checked everything out this evening and found that I could not get the blower to stop running and of course it wouldn't light. Checked everything beginning at the thermostat and I found that the manual reset limit switch on the lower right (as you're looking at the furnace) just above the gas manifold, had tripped. I reset this switch, turned the power back on and found that the fan was no longer running all the time. I set the thermostat to check and see if the furnace would light ok, and it did. Flame color is nice and blue and everything seems to be working fine. Furnace cycled off like it should. What would cause this particular reset switch to trip, and what else should I be looking for if the problem re-occurrs? Thanx in advance.
Most furnaces have a photo cell if it gets dirty the photo cell does not see a flame so it trips the reset button on flame failure.
Posted on May 21, 2008
thanks for your question, I am mr.grzz,
there are to reasons your furnace is doing what its doing, either a stuck pressure switch, or a bad flame sensor, replacing the pressure switch is pretty easy, its a little round flat peice with a tube sticking out of it, if you take the tube off and **** into it, you will hear a little click, try running your furnace while doing this, if it lites off, then bingo, but you have to make sure you have sucktion to the switch !
now the othe thing that I mentioned is the flame sensor, another relitive easy part to replace, its the pencil thin rod that stick up in front of the burners, when the flame ignites, it impinges on the rod which lets you gas valve stay open, if it has a little buile up on it, it might not send the correct signal back to the gas valve, taking it out, and cleaning it with emery cloth normally does the trick, try that, hope my info was helpfull, thanks again for your question, mr.grzz
Posted on Jan 21, 2009
Can you see the spark? It shoud be around about 1/4" gap. Make sure the igniter is sparking on the burner. Can you smell gas or hear the gas coming on? The pilot if it has one could be dirty or if it does not have one then the main burner cross over may need to be cleaned. Be careful and stand away from the heater while checking.
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Posted on Jan 02, 2017
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