The blower is going nuts

[halapeno]

Even with the system switched to off on the thermostat, the blower turns on about every hour for 5 minutes or so. I replaced the thermostat, but the symptom still persists. There is no problem with either heating or cooling, but I can't figure out how the blower can turn itself on without control from the thermostat. Any ideas?

[troyorr]

Why did you replace the thermostat? Which blower areyou talking about?

[mark beiser]

What thermostat do you have?
Does your system have a fresh air intake, with a control system for it?

Some thermostats have a "circulate" setting that will run the fan periodically to circulate the air in the house.

Some fresh air intake setups will run the system fan, independent of thermostat calls.

[halapeno]

I replaced the thermostat because it appears the only thing to have control ove the blower. The blower is located in the furnace unit.

There is no fresh air circulation and there are no settings for the blower on the furnace.

[mr horsepower]

does it have a draft inducer motor on the furnace or is it an older style, direct vent furnace? (when the blower motor you hear running when you feel it shouldn't be, is that accompanied by air coming out your supply registers?) if its an older furnace, you could have a problem with your fan limit control. we need some more info. by the way, i'd recommend getting someone out to look at it vs. just replacing parts that you don't know if they're bad or not. it might end up costing you more and will possibly create further problems for whoever ends up having to fix it in the event you can't.

[troyorr]

Looks like changing the thermostat didn't have any control over the blower.

[Dave-B]

How long have you had this system?
How long have you noticed this symptom?
Is this a furnace and A/C system or Heat pump?

My first Impression is that there is a fresh air control bringing on the blower.

[bahvaco]

Is it a gas furnace with a standing pilot?

[Senior Tech]

is call a pro to check it, you've already wasted money on a tstat, don't waste anymore.

Sorry, no diy on the site.