[av8rjudy]

Have a Goodman GUPS 100-3 Furnace. I can hear the motor turn on when the temp goes below where the thermostat is set - but no air is being blown through the vents. (I have a forced air systerm.) The vents are OK since my air conditioning unit goes through the same vents. The pilot light stays on and my gas stove works fine. The circuit breaker is OK. Any suggestions before I call a repair ($$$) man?

[labman]

Is what you hear the blower or just the little one that supplies combustion air? Without a good flow of air through the heat excanger, the furnace should shut off.

Check your ducts. Maybe plenty of warm air is exiting the heat exchanger, but leaking out a hole in the duct work. Start with checking the returns for a good air flow. Good flow at the return, and poor flow at the supply, means a duct problem.

The heating and cooling use different controls and a different winding in the blower motor. It can work with one, but not the other. The squirel cage could come loose from the fan shaft.

[av8rjudy]

Thank you for your response. Unfortunately I don't know the difference between the sound of a blower or just a little one. I can, however, hear whatever is turning on, when I'm on the first floor and the furnace is in the basement. My ducts were just cleaned, so that part is OK. Maybe the cage door for the squirrel got loose and he got out (I didn't even know one lived in my furnace)!

[labman]

The squirrel cage is missing the end, so the squirrels always get away or go hide. If there is a switch by the furnace, turn it off. Then set the thermostat to heat. Go back down and turn the furnace switch back on and listen. The first thing you should hear is a small blower. A few clicks later, the gas should come on, you may be able to see the flame through the louvers. In a minute or two, the larger blower that supplies warm air should start. Unless it pulls the heat out of the combustion chamber, the furnace should quickly over heat and shut down.

It the ducts are in the basement, you should be able to look them over and easily find any major air leak. It is possible the duct cleaners knocked a bunch of crud loose allowing it to plug something up, and put new air filters in.

[av8rjudy]

I did all the things you suggested. I heard what I think was the smaller blower come on and I waited 5 minutes and I never heard another blower come on. Could the motor to the larger blower be broken?$$$ (Whoever you are abman, you sure are a nice guy.)

[labman]

If the gas never came on, the pressure switch that tells the controls the litte blower is running is bad, or the controls are. If the gas came on, but went back off again soon, either the sensor that says it lit is bad or there is a problem with the blower. One thing you could do is turn the fan to the on position. If it doesn't run, you have a problem with it or the controls. If it does run, try a heat cycle. If the gas comes on and stays on, you have a problem with the fan or its controls. Heat uses a different winding in the motor and a different relay to control the blower than fan on and cooling.

Thank you for the kind words. I came here because I love dogs and wanted to share some of the excellent training I have had about them. I have very little training in HVAC, but saw many questions I could help with. So many, I don't even get my own projects finished.

[av8rjudy]

Dear Abman - I'm not sure how to see if the gas came on - I can, however, see a fan working through the louvre door. This happens when I turn the thermostat to 'heat' and it happens when I press the 'on' button rather than 'auto' on the thermostat. But alas, no heat comes through. Want to come over and fix it? I'm in NJ.

[labman]

With the pilot on, the gas should ignite with a whoosh if it comes on and continue with a low roar. You also should be able to see flames. If the blower doesn't come on then, the gas will shut off.

[av8rjudy]

The pilot light stays on, but there is no whoosh and no low roar. I see no flames other than the little pilo light. Any more ideas, my mentor?

[NorthernHeat]

The little pilot light may have a flame sensor. If it is dirty it doesn't pass current trough the flame. So the furnace doesn't know the pilot is present and won't open the main valve. WHen was the last time you had this furnace checked and serviced? These modern furnaces should be done about every 3 years. In the midwest a check and service should be right around $95.00 allot cheaper than a night or week end call because of no heat in the dead of winter. Believe it or not a good service tech knows what to look for on most furnaces to prevent breakdowns, we are not all "sharks" not to mention the safety inspection should be done. I won't scare you with the number of heat exchanger failures in a Goodman/Janitrol furnace.

[av8rjudy]

Thanks Northern and Labman - It's been ten years since it's been cleaned (oops! - huh?). I hope you're right about the dirty flame sensor. The HVAC guy is coming on Monday - I hope he's as nice as you guys. Thanks for all of your help.

[NorthernHeat]

Good luck and let us know how it turns out. I'd be happy to help you best I can, should he be trying to take you for a ride. PS you don't have to tell him there is a no heat.