Lennox P-8-9490 Transformer Burned Out - HVAC - DIY Chatroom Home Improvement Forum

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Old 07-04-2011, 08:20 AM   #1
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Lennox P-8-9490 Transformer Burned Out

Two days ago I discovered my AC no longer working. The house thermostat indicated it was not receiving any voltage. I traced this back to the blower transformer which was not sending out any voltage. Input to the transformer was proper (110V).

Yesterday, in a pinch because of the holiday, I installed a Honeywell 25V 40VA transformer which I expected to work until I could get a replacement P-8-9490 transformer. The Honeywell also burned out. Is there any reason for the Honeywell to also burn out?


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Old 07-04-2011, 11:37 AM   #2
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You have a short that is burning out the transformers. must fix short before installing another new transformer.


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Old 07-04-2011, 04:57 PM   #3
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check the wires to the outdoor unit. may be damaged from weed whacker, dog chewing, brittle and insulation missing and shorting.

also I would splice a 3 or 5 amp GM auto type fuse with blade terminals into the wire from the trans/secondary low voltage side so the fuse pops while you are short searching. can attach the wire to the fuse with spade type stakons from radio shack or the auto parts store.
"Cut it twice and it is still too short".
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