Hi all and thanks in advance for any advice you can offer. I apologize for the length of this post but my hope is that I can give you enough info to have someone connect the dots on what seems to be an oddball problem.

I have an American Standard Alligence 11 a/c system (Model # 2A7A1030A1000AA) that is ~11-12 years old. We're in SE Michigan so we don't use the system too often.

Last summer the condenser fan motor failed (bad bushing). It took 3 motors before I found one that was reasonably quiet. The replacement motors were creating a very loud harmonic noise in the grill.

The system will run fine for 10-12 hours. It maintains even cooling to the tstat set point (70 degrees). Eventually we notice the house temp is rising. The tstat shows 73-74 degree inside temp and the furnace blower is running but the condenser is quiet.

I have checked for a tstat signal at the contactor. I have 24v and if I pull the tstat wire off, the contactor cycles open/closed as I make and break the connection. I have line voltage at the 2 legs of the contactor on the input side and on the output side to the motors.

I have replaced the capacitor (45/5), contactor and fuses in the disconnect. I tightened the lugs on the breaker in the service panel (one was loose). The condenser fins are clean.

If I turn off the tstat for about 1 1/2 hours the system will restart and run fine, although in the last 24hrs it is now only running for a few minutes before the condenser shuts down. The fan motor is very loud initially and it cycles on/off 2-3 times in the first couple of minutes. Once it's running, the motor quiets down but it's not as quiet as it should be.

Could it be this replacement fan motor? It's a generic Fasco brand, 1/4hp, 1.8a, 1075 rpm. The original motor was a 1/8hp, .9a, 1075 rpm. I'm reluctant to condemn the motor because I'm operating under the assumption that the compressor and fan circuits are independent of each other and if one failed the other would continue to run until maybe a thermal limiter kicked in. Bad assumption?

I'm lost. Any ideas would be greatly appreciated.

Barry

 

Welcome to the forums.

If the contactor is closed and the compressor isn't running.... it's out on high heat or overload.
A fan problem will definitely cause that. It must fixed quickly as the compressor shutting down on overload is hazardous to its health.

If after replacing the motor is was still noisy.... you may have an issue with the blades.[TABLE="class: iws_table, align: center"]
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MOT08895 Condenser Motor
1/4 HP, 200-230/60/1, 1075 RPM, PSC, 42 Frame, CCW, Ball Bearing
REPLACES: 5KCP29JCA053BS / D151269P01 / X70671643010
Capacitor Size , 5 uf mfd @ 370 VAC