Rudder trim failure-looking for schematics

[IvanP]

I am troubleshooting rudder trim on 1990 Bravo. Worked fine on T/O and during flight, but when I tried to neutralize the trim for landing there was no response to panel switch, stuck in almost full left position for descent. My first thought was actuator failure, but the motor is fine. I was able to neutralize the trim in the hangar by applying power directly to the motor and it runs both ways. L limit switch is OK, R is inaccessible from the tail so I will have to find the time to drop the belly pan and get to it. Panel switch checked OK, but only the bottom half gets 24V on the common terminal. 

Unfortunately, I do not have the electrical schematics for the plane to chase this gremlin. Does anyone here have a pdf copy of the wiring diagrams to share? Any help would be greatly appreciated.  

Regards,

Ivan

[carusoam]

Ivan,

Do you have the ship’s rudder trim fighting with a new GFC500 rudder yaw damper system?

There are discussions of how to best operate the system to keep the two from fighting…

Sounds like you have something different going on… just wanted to let you know of this other more common situation….

Best regards,

-a-

[IvanP]

Thanks for the suggestion, Carusoam. My AP is old KFC150  - no rudder damper here. I think that this is an electrical issue of not getting power to the motor. 

Regards,

Ivan

[affricate]

8 hours ago, IvanP said:

I am troubleshooting rudder trim on 1990 Bravo. Worked fine on T/O and during flight, but when I tried to neutralize the trim for landing there was no response to panel switch, stuck in almost full left position for descent. My first thought was actuator failure, but the motor is fine. I was able to neutralize the trim in the hangar by applying power directly to the motor and it runs both ways. L limit switch is OK, R is inaccessible from the tail so I will have to find the time to drop the belly pan and get to it. Panel switch checked OK, but only the bottom half gets 24V on the common terminal. 

Unfortunately, I do not have the electrical schematics for the plane to chase this gremlin. Does anyone here have a pdf copy of the wiring diagrams to share? Any help would be greatly appreciated.  

Regards,

Ivan

Try this,

M20M Wiring Diagram.pdf

[IvanP]

Thank you, Affricate. Much appreciate your help.

Regards,

Ivan 

[IvanP]

How did you fix yours? By process of elimination, I think that it is the R limit switch on mine (cannot get to it until I drop the belly pan). Everything else seem so check out OK. 

[IvanP]

Problem solved. It appears that at some point when brake fluid was refilled some spilled all over , including the trim limit switches and all was gooped up. Good cleaning fixed the issue and all works fine now.