Coleman furnace blower

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  #1  
Old 11-02-08, 02:55 PM
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Coleman furnace blower

In the cold months, the furnace runs a cycle and a little later, the blower comes on and blows cold air for about an hour....also does this in the summer when it's totally turned down. There's no air conditioning or anything else hooked up to it....just the furnace. Any help appreciated and thanks in advance.
 
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Old 11-02-08, 07:45 PM
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There can be a few things that is causing this..

-Do you have any other control near t-stat or the furnace?

-Do you have an Air Exchanger/Heat Recovery Ventilation?

-Maybe the t-stat.. Make and brand?
 
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Old 11-03-08, 07:08 AM
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Thanks for the response. There is no other control near the t-stat or the furnace. It is ventilated correctly and just put a new honeywell t-state and new t-stat wiring on, as that's what I thought the problem might be. Still does it......
 
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Old 11-03-08, 07:19 AM
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At the furnace where the t-sat wires hooks up, tell us is hooked up there, and how many wires.

Example.
R-one red wire.
W-one white wire.

Ect.. ect..
 
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Old 11-03-08, 07:48 AM
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It's 18/2 t-stat wiring..one R, one W.
 
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Old 11-03-08, 08:34 AM
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I bet you may have a "blend-air" system.. it brings fresh air into the home every now and then.

Do you have a control like this on your furnace?


Here is the manual for it for you to read up on it if there is nothing left behind.
http://www.mobilehomerepair.com/medi...-8171Boper.pdf
 
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Old 11-05-08, 06:47 AM
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I do not find anything close to that on this furnace...the model is: P*UR/FG9-UP/G9T-DH 40-140 MBH Input...I may just end up having to have another tech check it out....thanks for the input.
 
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Old 11-05-08, 05:41 PM
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Then it might be a fan switch that has gotten more sensitive or weak now, and trips on at lower temps. My own furnace will do that sometimes after my house warms up during the day when I am away. Another common problem is after the furnace has run it's cycle and the blower shuts off, the blower can start back up again due to the fact the heat exchanger has released more heat out of its core. The only thing that is odd is that yours lasts for an hour. But I suppose it is possible under the right conditions in a particular house,........


........... if say the stat was satisfied, and the blower shut off because the fan switch area was cooled to the fan OFF setting. Then the blower starts up again because the core is releasing more heat at the fan switch area. And it stays running because the temp in the house is now a hair hotter than what it was when the stat shut down and because the fan(blower) ON setting is now lower than it used to be. And it keeps running that way for an hour until the temp in the house comes down enough so the inside of the furnace is cooler enough to shut off the blower whose fan OFF setting is now lower, due to a weakness in it.

If you happened to have one of those Honeywell fan-limit switches that has the temp settings on the dial, I'd say to bump up both the OFF and ON settings some (no matter what their current settings say they are, as they could now be out of calibration), and see if the problem goes away. If you have bimetal type switches that warp, say a thermo disc or some other type switch, you could remove it from furnace and test with blow dryer, by aiming heat at fan switch and thermometer at same time, while you have ohm meter alligator clipped on the terminals, to see if the on and off settings are to spec.
 
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Old 11-08-08, 08:07 PM
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Thanks to all for the input...had a tech out that seem to know something this time....had to bump up the limit switch and seemed to take care of the problem. Thanks again.
 
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