I had a new variable-speed high efficiency Bryant furnace installed last December.
This cooling season I've been running the fan 24\7 and it's been much more comfortable than my old furnace. A few days ago the wife & i noticed it felt a bit warmer inside even tho the Thermo said the temp was correct. Today i realized the fan wasn't running all the time--only when the compressor was.
I think I'm going to have the installer come back to look at it while still covered but other than a broke thermostat wire what could cause the fan not to run constantly when set to "ON"?

Does the computer have the ability to stop the fan? I checked the pilot light & it's not flashing any codes.

 

That would be the fault code light. No pilot light in that unit.

Usually with most thermostats.... when in "FAN ON" mode or cooling mode.... the blower is controlled by the same wire which is usually G.

Can you post the make and model of the thermostat ?

If you have a voltmeter you could check for 24vac between C and G at the control board. The blower should be running with 24vac present.

Since you have a newer system with a variable speed blower.... the "FAN ON" could be controlled by the G connection for a slower speed and the cooling would supply 24vac to the Y connection for higher speed.

 

T-stat is a Sensi by Emerson. Not sure of the model number but I'm pretty sure there's only one.

 

How do YOU test a digital t-stat when "opening" it means separating the stat from the wired base?
I could bench test it with another 24vac power source but is that the most practical way?

 

I would test it at the furnace control board.

 

I did mention at the control board in my reply.

 

Ok here's where it gets weird. I took the cover off the furnace and the blower stopped. It was running so slowly i couldn't tell it was on. So that seems to be what changed--but how\why did it change? All summer right up till a week ago the fan ran at a highish speed and i couldn't tell the difference whether the compressor was running or not.

Can i "tell" it i liked it better when the fan ran fast? My ducting isn't the best and i don't get much flow upstairs.

 

Yes... there is a safety switch that the blower door presses on. You have to hold the button in while testing. Sometimes a piece of duct tape will work to temporarily hold it.

Without knowing the make and full model number I'm not sure about the fan speed control. I'm not sure I'd recommend changing it anyway. It was working on higher speed and now it's not may be a control board problem.

 

I think I'm back to having them out to look at it. Something doesn't add up but it might be my lack of understanding how the furnace controls the fan speed. This furnace was installed when I was at work so I didn't get to ask any questions.
I also want to chew their ear about why they installed it facing the wall (dark & cramped) rather than the aisle where there's plenty of light & access.

 

7/28 the installer came out and showed us that the thermostat DOES set the fan speed. Odd thing is the setting is only visible when the 'stat is set to AUTO mode--which I have never used. Coulda been a power glitch. Now I know how to check/set it. If the 'stat had come with a manual instead of a web link I might have known about this hidden feature.

While there I asked why my filter after 6 months looked nearly clean but our floors are dusty. He got out a flashlight and showed us that there IS a very fine coating of particles on the filter. Since we have a dog I expected more. He suggested we have our ducts cleaned, and only replace the 5" filter annually.
I don't know where I got the idea that duct cleaning is a waste of money.