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 Repairing and Servicing Lennox Products
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 Erratic fan operation
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wildcatfan7

3 Posts

Posted - 08/15/2007 :  8:13:50 PM  Show Profile  Reply with Quote
I am having a problem with the fan on the indoor unit of my lennox system. The outside unit is a Lennox HP19-411-4P ser # 5192813380 and the inside air handler is a Lennox CB@ 18-41-3P ser # 5192D75901.

The fan has an intermittent sound that sounds like it is trying to speed up momentarily. This happens about every 5 seconds. It happens whether the thermostat is in the Auto or On setting.

I had a friend look at it over the weekend, he pulled the air handler fan motor relay (part # P-8-10283), it was chattering when we pulled the cover. He tested it by applying an external power source at his shop and told me that it was operating but that it was “going bad”. I reinstalled the part and ordered a new relay from this site.

From these general symptoms does it appear that the new relay will solve the problem or is there something else I need to address?

I have cleaned the inlet side of the air handler coils .

The outside unit appears to be functioning properly.

I had the freon checked and it is not low.

Am I harming the system by running it in it’s current state while waiting for the part to arrive?

The air handler has a tag on it that says it is certified for use with “split systems” and lists a series of HP18 and HP20 units. I note that my outside unit is an HP19 but in the 14 years we have lived here I have only had one other problem and that was replacing the circuit board on the exterior unit.

Any help would be greatly appreciated.

mark wallace

Cozy.Support

5821 Posts

Posted - 08/16/2007 :  3:45:16 PM  Show Profile  Reply with Quote
It could resolve it... if it doesn't, your probably experiencing some "fan hunting" that happens on some systems. There was never a systemic problem with the CB18 series having this issue, so a small change in static pressure or maybe re-centering the blower wheel or bending the blank off plate slightly in the discharge opening might help.



Cozy.Support does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx

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wildcatfan7

3 Posts

Posted - 08/21/2007 :  4:54:14 PM  Show Profile  Reply with Quote
I received and installed the motor relay. No effect on the sound.

Unit did not make the noise prior to cleaning the intake side of the inside unit coils. I re-examined the fins on the unit and did not find any bent.

After some experimenting I can eliminate the sound by doubling a bath towel and placing it over the intake vent. Stops the noise but severly restricts the output.

I have tried several differnt types of filters with no effect.

Does this fan unit (the inside air handler is a Lennox CB@ 18-41-3P ser # 5192D75901) have a second capacitor that is used for run after startup? And if so could that be the problem. Dosen't make sense to me.



mark wallace
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Cozy.Support

5821 Posts

Posted - 08/22/2007 :  06:21:20 AM  Show Profile  Reply with Quote
Yes, it should have a capacitor.

Did you look at the fins on the coil or did you look at the blower wheel? In particular, did you make sure there was no debris on the inside of the blower wheel?



Cozy.Support does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx

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wildcatfan7

3 Posts

Posted - 08/22/2007 :  5:16:15 PM  Show Profile  Reply with Quote
When I cleaned the coils I removed a lot of dust and mold. At the same time I also cleaned a lot of debris off of the blower wheel blades (front and back sides). I cleaned the blower with a tooth brush and the fins of the blower with a soft vacuum cleaner brush and water. I sprayed the fins and lightly brushed them out to prevent bending any. Then I vac'd up the water/soap. I made sure on start up that I did not suck any soap solution into the blower motor.
All registers in the house are open, I've tried going around and closing indivual ones to see if that would eliminate the pressure difference. No luck.

Am I right to assume that since the motor is starting and running that the capicator is OK?

mark wallace
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Cozy.Support

5821 Posts

Posted - 08/22/2007 :  8:28:37 PM  Show Profile  Reply with Quote
I would agree that the most likely the capacitor is good.



Cozy.Support does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx

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