Mooney Electric Trim Problem

Perhaps someone here can suggest where to start looking for this
problem:
Ocassionally, the electric trim on my '78 Mooney 201 will stop working
for "nose up". When I press the button and push forward the trim will
run nose down, buy the other way - nothing. While I have the button
pressed, the manual trim wheel is difficult to move (like it in being
engaged by the electric motor), but when I let go the trim runs fine by
hand.

I have had this happen a couple of times now, and I am stumped. During
the preflight I run the trim full forward and back and it works fine.
At some point in the flight it goes out. Voltage on the bus is 13.9, so
there is no problem there (unless there is a huge drop at the motor).

Anyone here experienced something similar, or have any pointers?

Thanks
Ian
N201ZV @ LZU

Are you a member of the Mooney email list? If not you should be. Go to
aviating.com, click on "Mooney" and sign up. They will have an answer
for you. You can email me privately if you have further questions.

Jon Kraus
'79 Mooney 201
4443H @ TYQ

wrote:

Perhaps someone here can suggest where to start looking for this
problem:
Ocassionally, the electric trim on my '78 Mooney 201 will stop working
for "nose up". When I press the button and push forward the trim will
run nose down, buy the other way - nothing. While I have the button
pressed, the manual trim wheel is difficult to move (like it in being
engaged by the electric motor), but when I let go the trim runs fine by
hand.

I have had this happen a couple of times now, and I am stumped. During
the preflight I run the trim full forward and back and it works fine.
At some point in the flight it goes out. Voltage on the bus is 13.9, so
there is no problem there (unless there is a huge drop at the motor).

Anyone here experienced something similar, or have any pointers?

Thanks
Ian
N201ZV @ LZU

This is a bit off topic but it does involve electric trim and I don't think
I ever gave the group feedback after asking for advice.

My Archer's electric trim was working except for the small problem of
tripping my over-voltage relay and taking the alternator off-line. The
suggested fix was putting a zener diode across the trim motor to shunt the
back EMF as the motor turned off. I never got around to making the fix but
instead stopped using the electric trim.

At my last annual the shop said they found a lot of lubrication points that
didn't look like they had been touched in years. After getting my bird back
I

1. PIOed the first landing because the yoke was working so freely and
2. Discovered the electric trim now worked without affecting the
alternator.

so the base cause was too much friction in the trim system.


wrote in message
oups.com...
Perhaps someone here can suggest where to start looking for this
problem:
Ocassionally, the electric trim on my '78 Mooney 201 will stop working
for "nose up". When I press the button and push forward the trim will
run nose down, buy the other way - nothing. While I have the button
pressed, the manual trim wheel is difficult to move (like it in being
engaged by the electric motor), but when I let go the trim runs fine by
hand.

I have had this happen a couple of times now, and I am stumped. During
the preflight I run the trim full forward and back and it works fine.
At some point in the flight it goes out. Voltage on the bus is 13.9, so
there is no problem there (unless there is a huge drop at the motor).

Anyone here experienced something similar, or have any pointers?

Thanks
Ian
N201ZV @ LZU