Lennox AC (10ACB) TurnsON /no Blower working on Furnace.

TommycAugust 22, 2014

Lennox 10ACB36-5P (1997)
Furnace is Coleman Evcon Model BGU10016A.
Thermostat Hunter Air Temp Plus Model 44422

I just turned my AC on first time in a year. The Lennox AC seems to be working fine outside the house. The fan on top of the AC is running smoothly and the unit seems to be running at normal speed. Inside, the ducts on the furnace are getting cold but the blower in the furnace to blow the cold air throughout the house is not working. I've left it on for an hour, no luck. Now, If I turn the furnace on to heat... the blower works blowing heat throughout the house. Just the AC can't get the blower to work in the furnace. Any help would be appreciated. I have all the manuals for the Lennox and my logic leads me to believe it might be the Start Capacitor C7, or the Potential Start Relay K31. Any help would be greatly appreciated.

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Turn the T-stat to 'Fan Only' and see if the fan works.

    Bookmark   August 22, 2014 at 9:32PM
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Ok... I'm getting somewhere. I turned the tstat from auto to fan. The fan worked. Then I turned on the AC. The AC is working and pumping air through the registers. Now I turned the fan only to AUTO... and the air is still on and the blower is working. I then turned off the AC totally. Switched the fan to AUTO and turn on the Air Again. Its working.

What does that mean? Do I need a new Thermostat?

Thank you in advance. Wow! I don't want to say genius, but heh... it sure seems like it! The do it yourself.com forum were suggesting circuit board failure and wanting me to do testing with the blower. So far... Thanks to you, maybe I won't have to do this.

    Bookmark   August 22, 2014 at 10:52PM
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pfoley... something funny here. I see you registered June 13, 2014. My birthday is June 14th... not 2014, but maybe this is meant to be. Hah.

    Bookmark   August 22, 2014 at 10:59PM
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Any suggestions on thermostats if I need one? I'd like to get one of those new types... like NEST, and some of the newer ones I've seen you can access through your cell phone in TV Commercials.

This post was edited by tommyc on Fri, Aug 22, 14 at 23:19

    Bookmark   August 22, 2014 at 11:16PM
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Can't say for certain your issue, but those Hunter thermostats are cheap low end and are known for being problematic.

I am not a fan of these lifestyle thermostats that sometimes can shortchange a high end system's capabilities. Definitely not Nest.

With an unmatched system like yours, I would just go for a good basic HW dig thermostat, programmable if you are inclined.


    Bookmark   August 23, 2014 at 8:13AM
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Thanks so far... I'm almost there. Now Its obvious I don't have the 5th C wire. I want to add another wire from thermostat and run it to the furnace. I can't get a hold of Coleman (Seems they are on an Extended Lunch Hour). I've included a pic to help you help me do the right thing here. I've traced everything correctly in showing the Thermostat and the AC wire. Tried my best in filling in all the blanks with the illustrations. Next to the 1-5 screws I have showed the color of the wire that is attached to each screw from the thermostat. Where should I attach the C wire that I am going to add to the new thermostat? What type of wire/guage should I get from Home Depot?


    Bookmark   August 27, 2014 at 1:46PM
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Go look at the existing thermostat and see if the terminals are labeled. Then write down the label->color arrangement.

    Bookmark   August 27, 2014 at 4:28PM
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Everything looks alright. I am the original owner and never had this motherboard switched out. House is 17 years old. Only thing is that it looks like the builder used a blue wire rather than a yellow.

So it looks like the 3 is the common... RIGHT?

This post was edited by tommyc on Wed, Aug 27, 14 at 18:05

    Bookmark   August 27, 2014 at 6:02PM
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Make sense?

This post was edited by tommyc on Wed, Aug 27, 14 at 18:07

    Bookmark   August 27, 2014 at 6:04PM
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How come the color of the thermostat wire bundle change from white to grey in the two photos? Is this the same wire?

It looks like terminal 3 has a red wire connected to it. Where does it go? Red is not a typical color for ground. Have you verified this with a volt meter?

Did you verify the thermostat is not energizing the G terminal when the fan is in the auto position and the AC is calling for cooling. If it is then the thermostat is working and the problem is some where else.

    Bookmark   August 27, 2014 at 8:17PM
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