Furnance blower won't shut off


  #1  
Old 06-11-02, 12:16 PM
Dan Meyer
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Furnance blower won't shut off

This last winter, twice, when heating, the blower would not shut off and of course, blows cool air. I have to then turn the power off to the furnance and back on. This shuts off the blower. It then works normal for a month or two.
A strange thing happen yesterday. I have the furnance thermostat set to "off" for now. The blower all of a sudden came on. So in order to shut it off, I had to turn the power to the furnance off and then back on.

Here are the thermostat positions:

Heat - Off - cool Auto - on

When the blower came on, the left control was on "off"
The fan position was on "auto"

What could be causing this, the limit switch or the fan relay. If so, where on the internet can I get these parts?

The furnance is a Lennox Model G12
 
  #2  
Old 06-11-02, 06:01 PM
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Hello: Dan

The blower motor may be turning on automatically because the ambient temperature is too warm at the furnaces location.

The temperature switch does not turn on the fan blower because the heater is on. It turns on independently because it is heat sensitive. Heat activates it regardless of where the heat is coming from.

Example: A furnace installed in an attic is exposed to a warm environment. If the attic temperatures reaches the set temp of the fan switch {Relay} it will turn the blower fan on to cool the internal firebox down.

Another reason may be because the contacts in the fan switch {Relay} are sticking together. Closed contacts allow current to flow and the fan turns on.

If you attempt any removal of the fan switch, be sure to turn off the electrical power to the entire unit first. Fan switches are wired into the house voltage. They are NOT low voltage parts.

For more detailed information etc. read the recent postings within this forum. These prior postings and any or all the replies offered within them contain almost all the required information needed pertaining to the many potential and or possible problems with the heating unit like your describing.

Additional Suggestions:
Read the manufacturers online web site for product information, problem possibilities, causes and solving methods, part locations, disassembly, reassembly methods, repair proceedures and instructions, pictorials and schematics, all or part of which may be available online.

An excellent source for orginal replacement parts is your local retail appliance parts store. Appliance parts dealers test and carry replacement parts for all appliances. Parts dealers are listed in the phone book under appliances.

Retail parts dealers can also help determine what the possible problem may be. Bring the make, model and serial numbers if you stop in at the store. The info will help to determine the ignition system and possible problem causes.

Several other resident heating and cooling professionals on this type of system, replying within this forum, could have additional helpful information, suggestions, advice. Check back on your question several times for additional replies.

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  #3  
Old 06-11-02, 06:07 PM
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heatcoolparts

dot com or org, not sure, find all kinds of stuff
 
 

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