Aprilair 550 on all the time

Old 12-30-07, 08:32 AM
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Aprilair 550 on all the time

New Years Greetings to you mods and members, I have a Aprilair 550 and last year I had my furnace replaced now the unit will constantly run without shutting off it never used to do this. I did replace the electric solinoid and no help. Could the contractor/installer connected the electrical incorrectely? I just went out and bought a complete new AA 550 to replace it. I will install it. But how would I know if the wiring is not correct to the tiny transformer?? I believe I can install this new one, I am a computer technician/installer by trade. Thank you!!!

I have one pair wires coming out of furnace to transformer then one pair from transformer to humistat then to soleniod it is a goodman furnace # GMS9

Last edited by thunder1951; 12-30-07 at 09:37 AM.
Old 12-30-07, 06:36 PM
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Location: Rochester, Minnesota
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Sounds like it's wired up wrong..

There should be a wire from HUM on the board going to the transformer.

Or no need of transfromer, there is a piggy back on the pressure switch (Brown wire), and that is 24 volts.

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