electric trim a one way street

[M Terry]

On my F, the electric trim only works in the nose down direction. No movement or noise from the motor. The mechanical trim wheel works normally. I'm going to go looking for the flaw this week. Anyone else have this issue? Where is the first place to look?

[warren.huisman]

Sounds like a broken wire somewhere.


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[carusoam]

A good time to pull the CB on that until everything is better known…

Nothing scarier than an AP that isn’t cooperating…

Start with cleaning the electric switches… an MS standard maintenance step…

Next step… add some detail about the switch… who built it, BK?

Take a pic of the switch… if it is a Bk switch… there is plenty of answers posted around here…

PP thoughts only…

Best regards,

-a-

[David Lloyd]

I couldn't find a schematic for the trim circuit.  Anyone?  For now focus on the connections from the trim switch to the trim switch relay.

[N201MKTurbo]

If it is a Century trim, I would wiggle the wires by the disconnect relay. Could be the wiring just about anywhere.

[warren.huisman]

I’ve had this issues a few times on my J. Twice it was a broken wire in the area of where the wire exits the yoke at the bottom and once a bad micro switch (1 of 3) in the trim switch itself.


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[neilpilot]

Not really on topic, but one of the most "exciting" post-maintenance flights was after a shop installed a rebuilt AP elevator servo.  I failed to notice the problem during preflight, and proceeded to climb to about 3k and then engaged the sTec 60-2.  When I engaged the altitude preselect to climb to 4k, the AP immediately entered a steep dive. I then disengaged, climbed to 4k, and with a 3k preselect the AP immediately began a steep climb.

Turns out the servo was wired in reverse.  My shop blamed sTec, and explained that the servo that's used in several different aircraft needs to be wired in reverse only for the Mooney installation.  I blame the shop, and also my inadequate preflight.

[Yetti]

Start with the simple things.  Contact cleaner the switch and the limit switches.   Then VOM and you will find it.   Just for fun we would take a trailer light blub Cut an aligator clip in two and solder the ends to the bulb.   Visual reference that one person can use.   You can see it light up on the floor if you were in the cab.

 

[N201MKTurbo]

5 hours ago, David Lloyd said:

I couldn't find a schematic for the trim circuit.  Anyone?  For now focus on the connections from the trim switch to the trim switch relay.

I posted them here years ago. Go look in the download section.

[N201MKTurbo]

8 minutes ago, N201MKTurbo said:

I posted them here years ago. Go look in the download section.

I just looked and they weren't there, so I just uploaded them.

[Yetti]

Mooney F 70s schmatics.pdf

I don't think the trim circuit is in here.   But it does show a co pilot plug.  Which is in my plane with nothing going to the yoke.   Also the flap switch is different that what is in my plane. 

Mooney F 70s schmatics.pdf

[M Terry]

the 2 short green wires that cross from lower pole to upper pole on the switches were both broken off.

 

[carusoam]

Great follow-up with a pic, M T!

Problem solved?

Best regards,

-a-

[M Terry]

I'm just using the manual trim for now. When I have time to get a mechanic over I'll get them to repair the connection.

[A64Pilot]

Might consider an Avionics shop, many A&P’s aren’t as adept with soldering as anAvionics tech.

[flyboy0681]

I won't recount the entire story now (it can be found somewhere here on MS), but about seven years ago I had a runaway trim situation that was scary has heck because I couldn't figure out what caused it. A few weeks later the same thing happened, this time I realized it occurred when using the trim switch. I eventually noticed that the nose down position was sticking, eventually resulting in my replacing the switch. Ever since that incident I keep my hand on the trim wheel making sure it stops.