Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 02-02-2011, 04:02 PM   #1
Newbie
 
Join Date: Jan 2011
Posts: 7
Rewards Points: 10
Default

Furnace fan on nonstop!!!!


Befor all you guys tell me that it is the fan limit switch let me tell you what i have been through already.

I was initially told it could be as simple as a bad tstat. so i replaced it with a new one. that did nothing. then i was told it was probably a bad fan limit switch so i replaced that. that actually fixed the problem; for awhile.
i decided to put my old tstat on to replace the one i had just installed so i could return it to my local big box strore. as soon as i put on my old tstat the fan began to run again and would not shut down.

Since that time i have reinstalled the new stat and a brand new fan liimit switch thinking perhaps somehow the old tstat did something to the switch suddenly causing it to fail.

now i am right back at where i started with a new tstat and new fan limit switch and a fan that will not shut off.

also i was told that if there are four wires going to my limit switch it is a low voltage application. mine does have four wires so i did break off the jumper to set for that application. unfortunately i broke the jumper off after the initial installation. now i dont know if i have created a new problem in that the fan limit switch was not initially set for a low voltage application.

any thoughts and ideas would be much apprectiated

crooked1 is offline   Reply With Quote
Old 02-02-2011, 07:08 PM   #2
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,060
Rewards Points: 3,784
Default

Furnace fan on nonstop!!!!


May have damaged something if you turned power on before breaking the jumper..

Post brand model number of the furnace.

beenthere is online now   Reply With Quote
The Following User Says Thank You to beenthere For This Useful Post:
crooked1 (02-02-2011)
Old 02-02-2011, 08:03 PM   #3
Member
 
Join Date: Aug 2009
Posts: 133
Rewards Points: 75
Default

Furnace fan on nonstop!!!!


When our old furnace (circa 1979) did this the cause was contacts within the Potter-Brumfield fan control relay that fused together under load. I had to snap the cover off the relay, pop the contacts apart, and dress them with a point file.

On a modern furnace the fan may or may not have a separate control relay.
MI-Roger is offline   Reply With Quote
Old 02-02-2011, 09:46 PM   #4
Member
 
Join Date: Jun 2010
Location: Peach state
Posts: 73
Rewards Points: 85
Default

Furnace fan on nonstop!!!!


You might have a short in your t-stat wire.
I had one last week that the gas would not shut off.
I took loose the white wire at the t-stat and the gas valve still stayed open.
Then I took the white wire loose at the furnace and the gas valve closed.
I put the meter on the white wire that was not connected to the furnace or t-stat and I had 27 volts.
You can do the same with the green wire to see if it is shorted out.
mikethe ductman is offline   Reply With Quote
The Following User Says Thank You to mikethe ductman For This Useful Post:
crooked1 (02-02-2011)
Old 02-02-2011, 09:52 PM   #5
Newbie
 
Join Date: Jan 2011
Posts: 7
Rewards Points: 10
Default

Furnace fan on nonstop!!!!


furnace is made by GE
probably from 80-81
furnace model is BLU106E936AO
thanks for any help or ideas
crooked1 is offline   Reply With Quote
Old 02-02-2011, 10:08 PM   #6
Newbie
 
Join Date: Jan 2011
Posts: 7
Rewards Points: 10
Default

Furnace fan on nonstop!!!!


I disconnected the green low voltage wire from the tstat at the furnace.
i set the tstat to call for heat and touched the two greens together at furnace and could hear the relay click
i believe relay is the right word but could be wrong fact is i dont think there is a short in the green line
crooked1 is offline   Reply With Quote
Old 02-02-2011, 10:16 PM   #7
Newbie
 
Join Date: Jan 2011
Posts: 7
Rewards Points: 10
Default

Furnace fan on nonstop!!!!


One other thing to add when i manually turn the dial of the fan limit switch i hear the click at fan on and at limit but i dont hear a click when the dial turns to fan off after system has cooled.
crooked1 is offline   Reply With Quote
Old 02-02-2011, 10:20 PM   #8
Member
 
Join Date: Jun 2010
Location: Peach state
Posts: 73
Rewards Points: 85
Default

Furnace fan on nonstop!!!!


The green wire should not bring on the fan in heat mode unless you have ele. heat

Sound like you have an old fan/limit combo.
When the furnace heats up it will close a set of contacts to bring on your fan
mikethe ductman is offline   Reply With Quote
Old 02-02-2011, 10:27 PM   #9
Member
 
Join Date: Jun 2010
Location: Peach state
Posts: 73
Rewards Points: 85
Default

Furnace fan on nonstop!!!!


Quote:
Originally Posted by crooked1 View Post
One other thing to add when i manually turn the dial of the fan limit switch i hear the click at fan on and at limit but i dont hear a click when the dial turns to fan off after system has cooled.

Sounds like the points open if not you would not hear them close.
BTW don't turn it by hand it should only turn when heated up.

mikethe ductman is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Lennox Furnace G27M Series Unreliable operation: pressure switch or else? sheppard1977 HVAC 7 01-14-2013 06:42 PM
Water Inside/Around American Standard Furnace michrob HVAC 8 12-08-2011 04:51 PM
Furnace Model # Feh-015-04 clicking but not turning on? haimei HVAC 1 12-14-2010 06:01 PM
Problems with new furnace..Overheating, having to reset. Furnace too big? Tommy2 HVAC 41 12-01-2008 02:55 PM
New Cased Coil - Install to Furnace - PICTURES!! hartkem HVAC 39 11-18-2008 02:45 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.