Roof air questions--now need motor info 5/6/14

Change the Capacitor and see if the A/C works. A bad capacitor will cause the AMP to spike on compressor start up.

Change the Capacitor and see if the A/C works. A bad capacitor will cause the AMP to spike on compressor start up.

Will a bad capacitor trip the breaker? Possibly yes. HOWEVER this next statement is a YES, no doubt about it.

IF the bad cap is the start cap, (Some motors have only a start cap, some start and run) then the motor will never come up to speed it will remain in "Locked rotor" mode drawing way more power than it normally draws and this will.

1: Trip the breaker and 2: Burn out the motor over time.

So either the bad cap tripps the breaker, or it causes the motor to do it, but either way a bad cap can make the breaker go CLICK.

The only way a bad fan a capacitor would trip a breaker is if it is shorted to the case- an easy test. Just pull the wires and test for continuity between terminals and case.
If it blows right away, it sounds like a dead short, or shorted fan motor. Either way, it's a matter of elimination- it could even be a short in the control box.

I have NEVER seen a capacitor cause a BREAKER to trip. Possibly to happen, but extremely remote. If you want a quick test to determine if the wiring from the breaker to the AC control is shorted. Take the 120 wires loose at the control box and stick the Black and white into a 12 gauge extension cord and run on FAN ONLY. Since you state it trips on fan only also, if the fan runs and the wall plug for the extension cord does not trip the breaker you have your answer. Since you state it does it on fan only also, it seems that the fan motor is the shorted part. You do NOT have to do the extension cord test if the breaker trips ONLY after turning the AC fan to on only if it trips all the time. Doug

I had already pulled the capacitors, had them tested today and they were OK. If the rain lets up by tomorrow I'll replace them and start testing the wiring. If it is the fan motor are there any shortcuts to replacing it? I'll look at it tomorrow but sometimes someone knows the easy way!!!!

Thanks for all the replies,
DICK

dometic model #: 600312.321

After replacing the capacitors I disconnected the 120v wires at the control box. Checked voltage from breaker--good. Stuck the black & white from control box into an extension cord and turned on fan to high--nothing & no breaker tripping. Then tried the fan at different speeds--low--nothing, med--heard a hum and then fan quit, still no breaker tripping.

DICK

acker1 wrote:
dometic model #: 600312.321

After replacing the capacitors I disconnected the 120v wires at the control box. Checked voltage from breaker--good. Stuck the black & white from control box into an extension cord and turned on fan to high--nothing & no breaker tripping. Then tried the fan at different speeds--low--nothing, med--heard a hum and then fan quit, still no breaker tripping.

DICK

Bad fan motor. Doug

Thanks Doug.

DICK

The pic has the info on the motor. I can't find the same one. The nearest is "Dometic Brand duo-therm Brisk Air Fan Motor Replacement Kit 3108706.916"
It shows 1/5 hp,A2.0 and the one in the pic is 1/4 hp.A3.5. Is this a good replacement?



Thanks
DICK