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Ruud AC fan won't shut off

Ruud AC/heater fan won't shut off, even when the thermostat is set to off. The limit control switch and the "Heat-Cool Relay" have been replaced. The system wiring seems to be properly connected and tight. And while I can't swear to it, when the thermostat is set to off, the seems to be no power going to the fan/blower - which continues to run on the low speed.

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It sounds like this is an electromechanical system, (no circuit board) verify that you wired the normally open switch at the fan limit control to the low speed fan, to the normally closed on the relay..(series circuit) if either of these are wrong the fan will runn all the time

Posted on Jul 12, 2009

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In many mobile homes this scenario is very common, less so in permanent homes, but here is how it works; The heat side of your fan which is the low fan speed is not dependant on the thermostat it's heat activated. Your already aware of this to some degree because you had the limit \fan switch replaced. I've taken that approach to that unit myself. In reality what probably is happening is on hot days your unit is warming up by being hit by sunshine and then it clicks the fan on at 140 degrees. This especially happens if the unit is on the roof or a split system in the attic. Remedies; run your A\C to cool it down, keep your attic cooler by way of an attic exhaust fan(which saves you cash anyway). Or if your not regularly using A\C turn breaker off til you need it. In the end there may be something going on, but odds are I'm dead on. Good Luck

Posted on Jul 12, 2009

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