Lennox blower won't come on - http://www.hvacmechanic.com/ Forums
Original message
| K-Man
 |  "Lennox blower won't come on"
, posted Wed 10 Sep 09:25  
I have a Lennox Merit G40UH, and the t-stat seems ok, a/c seems ok, but the indoor blower motor seems to be the only thing that won't kick on. I can get the t-stat to kcik on the flame jets, and can also get it to kick on the a/c compressor outside. But no blower. Also, cannot get the blower on when I move the t-stat to Fan-On. So I think I have it narrowed down pretty good.
The green LEDs blink out Normal Operation.
I am not too familiar with the wiring harness out of the control board to the blower. There are 5. White, Brown, Black, Yellow, Red. Can I pull one lead and connect a jumper from 120 VAC to test the blower straight out? Which wire(s) should I connect that to?
I have neglected the filter a while, and wonder if I messed this up. Never been good at changing them, but then again I never had a problem from it. This unit is 7 years old.
Thanks if anyone can offer any tips. I really hope this won't be an expensive problem!
Nick
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Replies:
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| learner
| "Re(1):Lennox blower won't come on" , posted Wed 10 Sep 10:57
Hi,
First thing is to see of blower is getting power when it is turned on by 'stat. Can you read schematics and use multimeter? If not,
it is beyond you. Call for service.
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| | K-Man
| "Re(2):Lennox blower won't come on" , posted Wed 10 Sep 11:40
I tested it with my multimeter, but I need a little help with interpretting the labels used by the schematic as far as the 5 wires going to the blower. I think it is down to the fact that the blower can be variable speed and maybe they all factor in.
But what I found was that one of the leads, the red one if I remember right (I am at work at the moment not at home), carries like 30 volts whether the blower is on Fan-On or not. When the Fan-On is selected at the t-stat, or if the A/C condensor is initiated at the t-stat, or if the heat ignition is intiated by the t-stat, in all cases I see no current coming down any other wire, though I do hear a click sound from the relay for the fan. Also, the transformer has 120 volts on one pole and 29 volts on the other, so I think the transformer is good.
Therefore, my opinion up to now has been that the board is somehow the problem. Whether there is a specific component on that board that is bad is maybe what I am looking for.
I do hear a relay click when the blower is supposed to kick on, but again, no current going down and of the other 4 wires.
And going back to my 1st post, I was really interested for my own sake to know which color wire I could jump to run it just to be sure it would run at all.
Does this help to put more context around my question?
Thanks again if you can offer any info!
Nick
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| | K-Man
| "Re(3):Lennox blower won't come on" , posted Wed 10 Sep 11:44
I added a link with pictures of the board and harness. Thanks!
http://www.flickr.com/photos/22843865@N02/
I wondered about the capacitor, but not sure if these symptoms point to it or not.
Nick
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| | beginner
| "Re(4):Lennox blower won't come on" , posted Wed 10 Sep 17:19
I am looking at some older Lennox systems. Do you see L1 and L2 terminals where the transformer is connected? What is the voltage? I think the blower motor is 220vac. There is one wire connects directly from either L1 or L2 to the motor; this is the common. Three other wires are for high, med, and low speeds. There are 2 lighter gauge wires for the capacitor. First measure the L1 and L2 and see what you get.
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| | K-Man
| "Re(5):Lennox blower won't come on" , posted Thu 11 Sep 11:32:
Not looking at it, I forget which is L1 and which is L2, but I get 120V at one and 29V at the other. Transformer is good I think.
The blower is a 110v, 3 speed.
The guy at an electronics shop said the area by the diode near the lower part of the board looks like it has seen water contact and charred the vicinity. He did sell me a new relay for the blower in case that's the issue (it is odd that there is no volatge going to the motor, when the relay clicks).
Back to the charred area on the baord - yes I bet water has dripped from the consensation drainoff hose mounted above the chasis, probably got in there. But if the microprocessor got fried, in theory, could the LEDs still be able to blink out Normal Operation? They show Normal, so I have to hope/think the chip survived! I think my reasoning is sound here....
Thanks :)
[this message was edited by K-Man on Thu 11 Sep 11:39] |
| | K-Man
| "Re(6):Lennox blower won't come on" , posted Mon 15 Sep 09:39
Problem solved. I traced it back to the 30A relay, which I had suspected previously. Removed it, tested, no response to the coil. Opened it up, found water damage inside! The drainoff hose has been trickling in through the louvers on top of the chasis apparently for years and found its way to the board.
Replaced the relay with a part from the electronics store and it runs fine now.
Nick
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