[Sonic09]

Hi all,

I have been searching through postings on furnace/thermostat problems all day and haven't come across the one I've been experiencing so hopefully someone out there can help me out.

I moved into my house last summer so this is my first winter with this furnace. It's a Heil gas furnace, I'm not sure of the model because I can't see it on the unit, and it was installed in 1995. My thermostat is a programmable digital Honeywell, CT3200A.

Okay, so the problem I'm having goes like this:

1. House is preset to say 72 degrees.
2. House is above preset temp according to the thermostat.
3. A little fan in the furnace starts cycling on for 5 seconds, off for 5 seconds, over and over and over. It sounds kind of like a car trying to start.
4. House drops below preset temp naturally, the burner kicks in, and the furnace heats the house up normally then shuts off for a while until it's little fan goes into its cycle again.

Now this fan is not the blower, and the cycling could take an hour or more which doesn't seem like normal furnace behaviour to me. Also, as soon as I raise the desired temperature on the thermostat, the furnace kicks in so it doesn't seem to need all those cycles to start up. In your opinion, would this be a thermostat problem or a furnace problem or both?

(As an aside, the settings for the blower fan on the thermostat are reversed (so in the Auto setting, the fan is on all the time, and in the On position, it goes on and off automatically - don't know if this is important at all or just a quirk).

Thanks in advance.

[hvac1000]

First the thermostat is wired incorrectly since the fan switch works improperly OR the thermostat is not compatible with the furnace.

It is also possible the furnace circuit board is causing the small draft blower to run when not necessary.

Both of these problems will need the attention of an On Site professionals visit to your home to diagnosis.

[Sonic09]

Thanks so much for your quick response. You were right on both counts. I had the furnace looked at today and it turns out that the fan control board was turning on the ventor motor inappropriately, and the thermostat was wired incorrectly for the blower fan. Both problems are being fixed by the technician. Thanks for giving me a head's up on what to expect from their diagnostic.

[hvac1000]

No problem I hope it all goes well.