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dmbrasket@hotmail.com 02-02-2008 10:55 AM

furnace blower keeps running
 
I have an old International forced air nat. gas furnace. I heat my home with wood mainly so it doesnt run as much as most homes. I notice that long after the house is up to temp and the heat exchanger is not hot, the blower runs and runs. I have read about limit switches and fan controls but dont know where to start. The only thing I did try was to remove the green wire from my thermostat but the blower kept running which I guess eliminates the thermostat. I cannot afford a new furnace at this time so I would just like to find out what is actually keeping the blower motor continously running. I know I have a dinosaur for a furnace but I need to fix this prehistoric beast.:furious:

chris75 02-02-2008 12:47 PM

Quote:

Originally Posted by dmbrasket@hotmail.com (Post 94296)
I have an old International forced air nat. gas furnace. I heat my home with wood mainly so it doesnt run as much as most homes. I notice that long after the house is up to temp and the heat exchanger is not hot, the blower runs and runs. I have read about limit switches and fan controls but dont know where to start. The only thing I did try was to remove the green wire from my thermostat but the blower kept running which I guess eliminates the thermostat. I cannot afford a new furnace at this time so I would just like to find out what is actually keeping the blower motor continously running. I know I have a dinosaur for a furnace but I need to fix this prehistoric beast.:furious:


Probably over your head but find the fan relay and find out why its energized...

UBoiler 02-02-2008 06:38 PM

Yes, if you have an electrical schematic for your unit, have good sense around electricity, have and know how to use a multi-meter, and have good analytical patience, you can probably track it down.

If all the above is no, ask or make a buddy with these talents and pay attention when he/she helps you. The archives on this site have similar problems and solutions. Let us know how it all works out. Good luck. Cliif

biggles 02-03-2008 10:56 AM

when you pulled the green at the stat was the system switched to heat with the fan in auto....if yes then the fan is on due to a closed limit switch thru the heating call.a quick cycle to heat is the stat calls...spark ignites pilot if older pilot is standing and the main gas comes on...the HEAT-X heats up and the fan switch closes to run heat into the space.stat satisfies main gas off fan removes the leftover heat from the HEAT-X and the limit opens up shutting the fan off shouls stay off till next call for heat...the disc might be fatigued but most of the time it will stay open on this state.if you can pull it to test it put your ohm meter on it and light a match under it or a lighter see if if reacts.if you have a HONEYWELL silver covered control that might be worn out it has 2 settings fan and HI limit in one!

dmbrasket@hotmail.com 02-03-2008 12:35 PM

blower keeps running
 
Thanks for the response...Yes, the switch was on auto and on heat when I pulled the green wire off and it kept on blowing. It is blowing right now in fact. Last night before bed, I shut the switch off on the furnace to shut it all down as well as setting the thermostat to off. I fiiled my wood burning insert and it kept the house at 65 F min.(16 F in mpls) Right now the temp in house is at 66 and I turned my thermostat down to 62 over a half hour ago and the blower keeps running. I want to remove my Honeywell limit switch and buy one @Grainger on Monday. It has a black dial in it for min and max. Yesterday I gave it a little touch and it must have a recoil type spring because it stayed right where it was when I tried to turn it. I have the schematic chart and it seems that it can only be a few things.

biggles 02-03-2008 01:12 PM

there should be 2 pins to set on that dial one/LEFT for fan on/off and the right/one for hi-limit temp...shuts the burner down.if you run the burner up that thing will turn as the HEAT-X gets hot..you should here a clicl when the fan comes on and it will will turn still but back down just above the fan on setting...but below the hi-limit tripon the HONEYWELL LIMIT CONTROL...IS THE WHITE PIN PULLED OUT if it is IN that is constant fan??????:eek: grainger has 2 brands Grainger #2E818 the different ones are the spring assembly probe lenght check your fot exact replacement www.grainger.com

dmbrasket@hotmail.com 02-03-2008 01:44 PM

blower keeps running
 
I went down to see my fan/limit switch but I don't see any white pin. It is a Honeywell with a blue wire running L to the fan and the other wire running R to the "limit". The switch on furnace has been OFF because the blower keeps running. Now... I slowly rotated the dial counter-clockwise and the blower stayed off. It is still off and the switch on the furnace is on. It shouldn't come on till' it calls for heat since I lowered the thermostat to 64 F. Does that sound like the fan/limit switch is the problem ? It sounds too simple to me.

biggles 02-03-2008 04:57 PM

note the setting that the limit is set at and that is what it should of done when the heat cycles off with the heat-x cools down.set the stat for 70F heating and check the action of the dial as the burner lghts up.it should stat to turn as the metal spring expands from the heat on it...and the fan should start for normal heating and running.NOW hut the gas off at the line coming into the unit...your simulating that the stat is satisfied,and the heat-x will start to cool off and dial will turn and the fan will shut off a the metal spring cools off on the limit,,if you need to turn it to get it off it needs to be changed.the pin for the FAN ON should be set between 160F-180F with HI limit 200F-210F...if the pin moves as it turns it needs to be changed!THE WHITE PIN useto cause problems when people would put te cover back on and push it in as the blindly put it on after servicing the unit...HONEYWELL might of removed iton latter controls


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