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Mark Henley
Mark Henley, Journeyman Technician
Category: HVAC
Satisfied Customers: 3217
Experience:  UA Journeyman Pipefitter , HVAC, Refrigeration, DDC controls. 26 years.Commercial & residential
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The fan keeps running even if the the thermostat does not call

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The fan keeps running even if the the thermostat does not call for heat.
The thermostat is a Honeywell ct3200 programable thermostat with forcednair furnace.
Any ideas?
Chat Conversation Started
Mark Henley :

Hi, this is more than likely a problem with the fan control in the furance, to check for that all you need do is remove the green wire from the thermosat, and see if th eproblem still exists, if ti does then its the fan control in the furance and nto the thermostat, let me knwo, thanks Mark, if this is a new themrostat install then its more than likely a problem in the setup of the thermostat, let me know what happens when you remove the green wire all together,

Customer : I removed the green wire and the fan is not coming on.
Mark Henley :

Hi, ok the problem is most likely in the setup of the thermostat, so let the heat run and see if the fan will come on when the unit heats up, let me know then we'll move on to the thermostat setup.

Customer : Ok , I'll let it heat up and see if the fan comes on.
Mark Henley :

Make sure that the dipswitches are both on and the the fuel switch is on F

Mark Henley :

leave the 3rd swtich off to see farenheit temperatures, so its 1 & 2 On and 3 off, then the fuel switch to F

Customer : Ok the switch was on E and all dip switched were ON, I put the switch on F and turned the 3rd dip switch to the off position.
Customer : Ok the furnace heated up and the furnace fan turned on.
Customer : It does read Celsius now , is that the 3rd switch?
Mark Henley :

Ok put the green wire back on and try it, the switch being on E will turn the fan on in heating, because the stat thinks it's electric heat and the fan will always run with electric heat energized, now that it's set to F which is gas heat the stat should let the thermostat control the fan in the heating mode, let me know what happens, thanks Mark

Mark Henley :

If it reads celsius switch the 3rd one,

Customer : Ok do I need to shut the power off to the furnace when I connect the green wire?
Mark Henley :

It's better to do that,

Customer : Would it be better to put the fan on Auto or on On position.
Mark Henley :


Customer : I put the green wire back on, then fan is still running but the furnace is probably still warm.
Mark Henley :

Ok let it cool down a bit,

Customer : Ok the fan shut off, so it looks like your fixed the problem.
Customer : Thank you very much
Mark Henley :

lol, no you fixed it.

Customer : Well thanks
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