Trane furnace - blower will not quit

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  #1  
Old 03-18-03, 08:01 PM
jfaught
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Trane furnace - blower will not quit

Hello,

I have a Trane "Executive High Efficiency" gas furnace, that was installed in 1987. It just started to have a problem where the blower motor will not stop running. The thermostat was replaced last fall with a new White-Rodgers digital, programmable model. I replaced the 2 "AA" batteries to no avail, plus replaced the air filter in the furnace. I really can't afford a new furnace right now, and I would greatly appreciate any insight as to whether this is something I can handle myself.

Thank you,

Jason Faught
 
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  #2  
Old 03-18-03, 08:10 PM
AVGJOE35
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I'm sure you've checked the obvious but is the fan switch on the t-stat in auto or on??
 
  #3  
Old 03-18-03, 08:27 PM
firsthvac
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Dear Jason...

We need a little bit more information about your furnace before offering some insight into your problem.

Does your particular furnace have a pilot light that is lit all the time or is the pilot flame ignited only when heat is called for from the thermostat?

Is the blower motor that is running the main blower for the entire house or is it just a little blower motor for the exhaust gases?


Barring the thermostat fan switch being set in the "on" position instead of the "auto", there are a couple of common causes for your type of problem.

A) The fan switch (which turns on from heat after the burners come on and goes off from the blowing air cooling it after the burners shut down) could be stuck in the closed position, in which case it would need to be replaced,

B) An ignition/fan control board has gone awry and will probably need to be replaced, or

C) There is a wiring short causing power to be applied to the motor, thus making it run continuously

Answer those two questions above and giving us any additional information about the furnace or it's sequence of operation will greatly aid us in assisting you better.

Thanks...look forward to hearing from you again
 
  #4  
Old 03-18-03, 09:02 PM
jfaught
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Thanks for your quick reply. The ignition must be electronic, because there is no pilot. The motor that is running is the large, circular housing in the bottom of the furnace cabinet. It is behind a door that has a shutoff switch that shuts the furnace off when removed. I've checked the t-stat and it is in the usual "auto" position. The only way to stop the motor is to turn off a shutoff switch located near the furnace, or to remove the lower door.

Thanks again,

Jason Faught
 
  #5  
Old 03-19-03, 01:17 AM
firsthvac
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Thank you, Jason, for the extra information. Your most likely suspect is the fan control switch (either the heat activated type or control board type) and will require replacement.

It is highly probable that the switch is a heat activated type. Because of the various switch types, lengths and settings, I don't recommend you try to replace it yourself. Call a good reputable licensed service company...ask your neighbors, friends and co-workers who they use and would recommend, as word of mouth is an excellent gauge of integrity and reputation.

Let us know what happens.
 
  #6  
Old 03-20-03, 05:59 AM
jfaught
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Hello,

I can't tell you how much I appreciate your help. I found a replacement fan control switch. The old switch was a Honeywell, and I found a White-Rodgers that is a direct replacment. I removed the old switch no problem, and it is the heat activated type with an 11" shaft on the back of the switch. The problem I've run into is that the wiring is slightly different on the new switch. The Honeywell had four wiring posts; The left side is marked "Fan", the right side "limit". The top posts are both marked load, the bottom posts are line. The new WR switch has the fan on the right, the limit on the left. The problem is that the new switch does not have markings for line & load. The old switch had a red wire in the fan load, orange in the fan line, then a grey wire in the limit load, and a white wire in the limit line. Is there an easy way to correspond these locations to the new switch? I'm not afraid to try myself, just don't want to damage any other parts.

Thanks again,

Jason Faught
 
  #7  
Old 03-20-03, 07:19 PM
firsthvac
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As long as there is not a common connection between one fan terminal and one limit terminal and there are only two wires for the fan switch and two wires for the limit switch, markings for line and load will not be a concern.

If there is a common connection (usually a stiff copper wire from the fan terminal to the limit terminal) you should be able to remove the connection and proceed with the wiring as described below. If you are not be able to remove the common connection, then get the exact Honeywell replacement before proceeding.

Put either fan wire on one fan terminal and the other fan wire on the second fan terminal. Do the same for the limit switch wires. Turn the power back on and check to see if the unit operates the way it should.

Hope this helps...let us know
 
  #8  
Old 03-23-03, 06:52 AM
jfaught
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Hello,

I installed the new fan control switch, and I'm happy to report that it solved the problem! I really appreciate all your advice and assistance.. you saved me alot of money! I don't mind paying for a service call, in fact I have a trusted repair person, but money is kind of tight right now and a new furnace just isn't in the budget. Thanks again and take care.

Jason Faught
 
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