I have a 15 year old gas furnace and a 15 year old programmable Honeywell thermostat, with heat and air.
The furnace is randomly failing to come on (heat or fan), until I turn the master furnace switch off then on. Even if I set the thermostat temp above the current temp.
The furnace then ignites normally, runs till the house reaches the thermostat temperature, then shuts off normally.
The repair man could find nothing wrong. He was a good knowledgeable guy but because when he was here everything worked, he had to leave without fixing anything. He checked limits, CO2, etc. All was fine. NO cracks, etc.
There is a hum from the furnace when it wont start. I then turn off the master and the hum goes away. Switch on, furnace starts.
Anyone have any theories? Could it possibly be the thermostat?
2007-12-01 10:57:45 · 7 answers · asked by cornmanz 1 in Home & Garden ➔ Maintenance & Repairs
It sounds like the blower motor is stalling part of the time. If it is a capacitor-start motor, you might get by with replacing the capacitor, other wise you may have to replace the motor. Also check (with the power off) to see that the motor and blower rotate freely and there are no loose parts that might jam the blower. Check for loose, corroded, or heat-damaged electrical connections. There may be an interlock that prevents the main burner from starting up until there is airflow.
2007-12-01 11:04:11 · answer #1 · answered by Tony 4 · 0⤊ 0⤋
It sounds like a relay switch may be sticking if there are relays in your system , its hard to troubleshoot with out knowing what kind of furnace and its normal operation sequence. the thermostat seems to be sending a call for heat and shutting off when it gets to temperature so I don't think that's the problem. Also there should be a wiring schematic on the inside of the furnace door look to see if it shows a relay somewhere in line
2007-12-01 19:26:35 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Switches get some sort of film on the contacts from time to time and they also wear out. Mine is 10 years old and I recently pulled it off the wall, replaced the battery and worked both switches between positions pressing down on the switch as I moved it several times to clean it up a little. It works okay now. Mine was doing it more when I was using the air conditioning in the summer. The 'heat cool' selector switch could be the culprit.
2007-12-01 19:22:20 · answer #3 · answered by normy in garden city 6 · 0⤊ 0⤋
I agree with Tony sounds like fan cap very carefully when it hums like that and doesn't start give the squirrel cage a nudge and see if the fan takes off if it does leave the fan switch on t-state to the on position until you can get a tech out there at least you will have heat
2007-12-01 20:09:25 · answer #4 · answered by dvdacmn 6 · 0⤊ 0⤋
Sounds like the fire eye is dirty on the furnace. Oil burners are a pain. You did change the filter, and insure you had good oil flow to it, correct? I once had to take compressed air and blow it into the oil tank from the oil line, it had become a bit clogged, and was partially obstructed, hence, my oil flow was poor. Once the line was cleared, everything was OK.
2007-12-01 19:04:03 · answer #5 · answered by joerides 2 · 0⤊ 2⤋
I'd say it's the thermostat. they do go bad- we've had to replace several at my church- same reason.
2007-12-01 19:03:40 · answer #6 · answered by Seeno†es™ 6 · 1⤊ 0⤋
Get a qualified professional to fix it. that could be dangerous.
2007-12-01 19:01:23 · answer #7 · answered by PeeTee 7 · 0⤊ 2⤋