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Old Nov 08, 2012, 06:35 AM
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United States, PA, Butler
Joined Jun 2006
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Furnace help

Hi all, I am not confident that the furnace repair guy is correct in diagnosing my furnace problems, plus they want to charge $292 on top of the $89 diagnostic fee to replace a 2 wire, 2 screw $20 part.

Here is what I have: Rheem Imperial ROBC-095QBEA updraft oil furnace

Here is what is happening....

Hear a click in the thermostat to turn the furnace on. Oil burner turns on and runs. Blower should turn on with a delay timer after a bit. Sometimes the blower turns on and sometimes it doesn't. Obviously, the oil burner kicks off soon if the blower does not turn on.

Other times it runs normal.

Some times, the blower runs out of normal sequence. It will all turn on normally, then instead of the burner shutting down and the blower running for a time to cool the heat exchanger down, the blower will turn off at the end of cycle while the burner continues for a short period.

Diagnosis was the limit switch, which could make sense if it was reading a wrong temp and shutting the burner down too soon before blower starts. The problem I have with that is with the times that the blower shuts down early at the end of cycle before the burner shuts down.

The furnace control that is wired up to the thermostat is seeing all the required voltages. The furnace guy adjusted the timer on the blower and it runs normal more often now, but is still a hit or miss whether it will operate normal.

Hoping someone could shed a light on what component could be the problem. My three thoughts are the limit switch sensing too cool of a temperature, the fan cycle control of which I can't find a good diagnostic page on the net, or the thermostat of which is relaying the proper voltages down to the furnace.

Thanks
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Old Nov 09, 2012, 11:30 AM
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United States, CT, Killingworth
Joined Dec 2005
1,831 Posts
Sure sounds to me like some sort of blower control issue if the blower is spotty or intermittent. My first step would be to inspect the connections for broken or loose wires, etc.

Following the troubleshooting flow chart in the installer's manual, it even says fan center (control) or motor/ start capacitor.

http://www.expresshvac.com/viewFile....all_Manual.pdf
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Old Nov 16, 2012, 11:49 AM
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United States, CT, Oxford
Joined Oct 2012
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Id first check what ever it is the controls the fans oreation. maybe its getting ready to die on you. you can check the wires for a short... It could be some simple thing thats overlooked cause its so simple youd never think of it.I had a furnace run on and on all night till it boiled over...all because a small piece of solder had fallen onto the control circuit and bridge the two wires that turn the furnace on and off making a complete circuit and keeping it on all night! lol that was fun!
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Old Nov 20, 2012, 01:47 PM
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United States, PA, Butler
Joined Jun 2006
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For closure, my furnace is fixed.

While trying to diagnose it, it was warm out. That means, kept having to turn the thermostat up to get it to cycle. It was running semi normal every time I tried to look at it except for the blower kicking out early. I turn it back up again and run back down to the furnace with a meter again, rinse and repeat.

Last week, it finally turned cold out. Woke up to the burner running and blower not coming on. Looked at the thermostat and it wasn't calling for heat. Clicked in my head and I gave myself a smack on the side of the head, the burner is stuck on, not that the blower is running out of wack with the cycle. The burner is stuck on and is just being shut down by the limit switch until it cools, then firing back up. Found the relay controlling the burner, gave it a tap with a screwdriver, and the burner shuts down.

$22 to replace the stuck relay.

I figure with it being warm out and not needing heat during the day, I would wake up to it acting up and go down and mess around inadvertently bumping the relay causing it to open, which then the furnace would stop and not come back on with it being warm enough not to call for heat from the thermostat.
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Last edited by mrodgers; Nov 20, 2012 at 01:53 PM.
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