Help! Furnace wont stop running


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Old 01-25-09, 02:38 PM
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Help! Furnace wont stop running

I have read several posts about this but I can not seem to get it fixed. I have a very old furnace (40 years) that will not stop running when the temp has reached its set level. The fan keeps running on low speed blowing cool air. From reading other posts, I thought it would be the fan control unit, so I put in a brand new one, with the low set on about 100, hight set on 140 and limit at 200. Same problem. I have tried playing with the controls but no luck. I am not very experienced in furnace repair but I was hoping to fix this myself. I have also tried tapping all of the control boxes, hoping to loosen a stuck relay, but that has not worked either. I unhooked the green wire from the thermostat and the fan still runs. Please help!! Thanks in advance. I have pictures of the furnace componets but there is nowhere to attach pictures. I can email them if someone out there can help!
 
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Old 01-25-09, 02:42 PM
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Pictures can be seen here... I am not sure where the relays are to check. Thanks

Flickr: KAARONA1's Photostream
 
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Old 01-25-09, 03:24 PM
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Is the white push button on the fan control pushed in? If it is then it should be pulled out because the fan will run continous with it in. You can try removing the fan relay under the silver cover of your fan center. If the fan stops when relay is removed then something is powering realy or it is stuck closed. That relay is for the fans high speed cooling so it won't affect the fan in heating mode if you need to remove it if it is bad.
 
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Old 01-26-09, 09:42 AM
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Originally Posted by hvacservicetech
Is the white push button on the fan control pushed in? If it is then it should be pulled out because the fan will run continous with it in. You can try removing the fan relay under the silver cover of your fan center. If the fan stops when relay is removed then something is powering realy or it is stuck closed. That relay is for the fans high speed cooling so it won't affect the fan in heating mode if you need to remove it if it is bad.

Thanks.. the button on the can contorl is pulled out. What exactly should I look for when I pull the silver cover off the fan center (I assume you mean the honeywell piece that is on the pictured labeled furnace controls???) I pulled off the furnace pieces to get into the fan, but there are no wires in there other than a constant power. What does the relay look like? Or should I just replace the other honeywell control unit?
 
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Old 01-26-09, 03:10 PM
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no heat running,only fan..pull the cover on that silver covered honeywell fan/hi limit control....turn the dial CWtowards the lower temp stamped on it the fan should shut off.is you stat in auto/heat if it doesn't shut off then that relay is stuck closed.pulling the G wire off the stat subbase won't shut the fan off because the fan on the heating setting comes from that fan limiter.has it been doing this since you replaced the limiter.....to test the HI LIMIT, run the heat and turn the dial all the way CCW(simulating fans not runnig) main gas burner should shut off.
 
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Old 01-28-09, 06:26 AM
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OK - I ordered a new Honeywell Relay R8222B and I will pick it up and install it tomorrow. Hopefully that does the trick! If the fan keeps running after I have replaced the Hi/Low Fan Control Unit and the relay... what should be my next move>??? Hopefully the relay fixes it, but just trying to plan for the worst. THANKS for all the help
 
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Old 01-29-09, 05:59 PM
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Fixed!!! Thank you

New fan control unit and new relay = solved!!! Thank you to everyone who provided input!!
 
 

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