Furnace will work fine for 8 to 10 hours, then after last cycle, will not restart. I have replaced the t-stat, and the on-off power switch at the furnace. I also found a short circuit under the mian power switch, and repaired that. Thought I had this thing licked, but it ran fine thorugh the night, then sometime this morning, the home began to cool off, and the furnace would not kick back on by itself. Now if I turn off the furnace, and turn off the breaker, then turn them back on, the furnace will kick back on and run fine for another few hours. This unit is a Coleman Presidential III 7900 series, standing pilot furnace.
You might want to check the filter, if the filter is restricting the airflow the furnace will over heat and it will shut down. if you turn it off and on it will reset it and it will try again. Pull the filter out half way and try that, if it runs fine then clean the filter or get a less restrictive one.
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Do not run contentiously during heat mode. the fan runs at a slower speed with heat and heat fires first then the fan cycles on during heat cycle then when heat satisfies the thermostat the heat will cycle off and fan will run for a couple more minutes and then cycle off. So set stat on fan cycle to auto.
Light the furnace with the lighter and allow it to cycle for a day, keeping it set for run. It should clear and the igniter work properly after that. If it doesn't, then is in the controller. But most likely will reset and clear within a 24 hour period or much less. It just has to keep cycling until it clears and resets.
Hi, these mechanical thermostats have what is called a heat antcipator on them. If you remove the cover you will see in increments or numbers such as 1.0, o.1, .2, .3, .4 or o.1, 2, 3, 4, . The stat and main gas valve work together and have to draw the same amount of amps to cycle the unit properly. This stat will have a copper arrow pointing at a number. A good place to start is to set it at .4. If the unit does not cycle right, set it at 1.0 and go from there until it cycles. Let it go through several full cycles during each time you adjust it until it is correct. These are good dependable stats as I have many on my service truck. If it doesn't take care of the problem, take it back and return it for one that is not faulty which happens often. Best of luck to you. Ps, the small manual that comes with a new stat has that information on it, anticipator settings. Shastalaker7 A/C, & Heating Contractor
if it is a mechanical thermostat the heat ant. does that on cheaper digital tstats it is set by span and on better stats like honeywell model 5000,6000,8000 series you set the cycle rate. what kind and model number is tstat
Sounds like your repair man ripped you off. He should have stood behind his work.
1. I would try to clean the flame sensor located just below the burners. It is connected to "one" wire (Not the two wire) clean rod with sandpaper.
2. The old and thermostat could have a had a bad heat anticipator. if the new t/stat is not digital the heat anticpator on the T/stat needs to be adjusted. slide the small adjuster arm under the cover to about .6 or .7 and see if the solves the problem. if the t/stat is digital it should be preset from the factory.
3. last resort have a service man check your pressure swith. could be a slow inducer motor, blocked or bad vacum line, or a restricted drain or flue pipe.
Is this furnace standing pilot or electronic? if standing pilot turn power off then take t-stat off wall and connect the wires labeled r and c together and see if that keeps furnace working. If electronic check flame sensor you can check flame sensor buy cleaning with steel wool. if that doesn't work then try t-sat.
if your furnace is on 24 hours straight, before it heats up your home, then either your cold weather and indoor temps are extreme, or your unit is grossly undersized. if however your furnace cycles on and off when the temp is still way colder than you have set it you have either a bad stat that thinks its hotter than it is, or a bad furnace problem and even though the furnace is getting a signal from the stat to heat it is failing to do so. you'll have to watch and think this through to isolate the problem. if you set the furnace to max heat and it runs and heats the house reasonably quick then its probably going to be a bad stat. if you set it to max heat and it shuts off way before it gets to setpoint then the problem is in the furnace. be sure filters are clean, blower wheel is clean , returns are no obstructed, etc. if you by chance have an old mercury bulb stat they had a thing in them called a heat anticipator which basically worked like this. a dial with a little pointer determined how soon it would be till the furnaced reached the desired temp and anticipated how soon to shut off the burners in anticipation of the cool down period so you dont overshoot the desired temp. if these are bad or moved to different setting they can short cycle the furnace on of on off etc. or shut down the burner almost as soon as it lights. setting is usually at .4 to .6 on most, but really a digital stat is only way to go. by the way check to be sure you don't have a hot air supply grill blowing directly on the stat or it will shut off as soon as stat gets hot and rest of house will be cold. usual location is 5 feet off floor directly over the main return air grill or under it as the case may be. good luck