AC blower continuously runs at high speed

[HernandoBeacher]

The blower motor on my Marvair AC blows on the highest speed whenever power is supplied from the circuit breaker. This includes when the Machair 1 thermostat is powered off. Switching the thermostat on has no effect on the blower but the unit functions normally otherwise.

In the old days, I would look for a burned out resistor block but the fact that the motor runs with the thermostat turned off has me stumped.

 

[kloudie1]

Blower power relay contacts stuck.. ?? One of the small black boxes on the circuit board.. is the relay.. there is another one for the water pump and another for the compressor..

 

[Bill Roosa]

there could also be a "blower on all the time" setting that need to be turned off. A lot of units have this feature to just move air around when it is coolish and you don't need heat or AC.

 

[kloudie1]

Bill is right, Hernando.. If it has always done that then find the owner's manual and work that setting.. Some units require a connection change on the circuit board and some have a provision in the controls .. If it just started doing that without your having changed anything, then ya probably have a component issue.. Happy Hunting !

 

[HernandoBeacher]

Thanks for the information. It ran fine all summer on the moisture control setting. I did not notice anything wrong until I switched the unit off and the fan continued to run. Sounds like Claude could be right guessing that a stuck relay could explain the absence of on/off control.