blower fan short cycle

[comfortable air]

a customer called the blower fan short cycle. when I got there , open the far compartment cover, take a thorough check. press the door switch, the fan work ok. but When I closed the door , just few minutes later, the fan start short cycle again.fileter is clean. when the fan is work, air is big.I measured voltage is 115v between the hotline and nuture of the fan moter when the fan is not working.so I think the fan overheated and thermal protection. checked the run capacitor, the rate is 15uf , but I measured only 5uf. changed the new capacitor. measured the current is 11.50amp( the old one is 12.5amp). the fan still short cycle. do you think the fan moter need to be change?

[coolwhip]

Make sure that you dont have a faulty door switch and that you have 115vac to the motor. Also make sure that its not a bad relay. Then replace the motor.

[comfortable air]

what i think is , if the power go to the fan moter( after the relay), the moter should be start, otherwise, it issiezed , thermal protected or not working

[Senior Tech]

Are you taking amp draw with the blower door on or off and what is the amp rating on the motor info plate?

[comfortable air]

the whole furnace current drawing is 13amp on the rate plate
is has not much different when the door or close. acutally I measured it when it the door closed

[Edited by comfortable air on 08-13-2005 at 10:58 AM]

[maxster]

make sure the stat is on "fan on" and not auto/fan it will cycle with the cooling.the motor was it hot to the touch when you first popped the panel

[comfortable air]

I put the thermostat down to minum and fan at on positon
what I can explam is when the door open, it draw much more cool air from the another cool room( the unit is hang at the another cooled room) , so it cool down the motor. if I closed the door , less air draw from the not conditioned room, and could not cool the motor. anyway , the motor thermal protection is very sensitive. what I think the motor is a problem is the power coming into the motor(I measured at the control board cool leader to the fan motor), when it is stopped working

[Edited by comfortable air on 08-13-2005 at 11:19 AM]

[maxster]

how are the squirrel rounds much dust on them,maybe blow out the motor windings(with nitro)if it is air cooled for access with thse openings on each end.