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Trim quit working

Rrhsch

Active Member
:confused:

Background:

RV12 with Gamin G3X w/GPS20A and Garmin GMC307 w/autopilot.

Trim was used and functioning prior to this flight. This was the first time I used Autopilot with a flight plan. I successfully used direct to with this autopilot prior to this flight.

While using the Garmin auto pilot on flight plan the autopilot brought me down to pattern altitude. I disengaged autopilot and slowed my RV12 for downwind leg and tried to trim for speed but trim didn?t work. Pushed autopilot disengage again to see if autopilot was still engaged. Still didn't work. Landed plane without the use of trim.

Actions:

1.Checked continuity of fuse-good
2. Checked wires on servo connection. Everything looked good.
3. Used external power source and moved servo in both directions.
4. Moved p trim screw 20 turns CCW and retested trim button.
5. Removed WH-00046 Fuselage harness and externally powered pins 31 and 32 with servo movement in + and - orientation. Replaced cable.
6. Removed switch harness cable. Removed pins 18 and 19 and reconnected harness. Put each pin to ground one at a time. No servo movement.
7. Repeated above with Autopilot on. Same result.
8. Turned Autopilot off and measured voltage to each pin (18 and 19) to ground. Each measured 4.8V each.

Conclusion:
I am able to make the servo function using external power source through the Fuselage harness. Pins 18 or 19 to ground do not cause the servo to move. I believe this simulates the same function as the trim switch. Please correct me if I am wrong. Assuming that this is correct the only part left to make the trim work is the AV-5000A logic box. Everything seems to function to and from the AV-5000A. I believe I have a bad AV-5000A.

Have I missed something?
 
Remove the Switch-Module-D-Sub connector from the AV-50000A CONTROL MODULE. Measure the voltage on pin 9.
Or even better, check pin 9 with a low wattage test lamp.

Check the autopilot D-Sub connector on the AV-50000A CONTROL MODULE.
Is there a jumper between pins 7 & 17?
Is there a jumper between pins 8 & 19?
If so, make sure they are secure and have continuity.
If there are no jumpers, but there are wires that go someplace else instead, then mark them and remove them.
Put jumpers in their place. Test the trim again.

If no problems are found, I agree with your conclusion.
 
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Yep, follow Joe's recommendations to see if the AV-50000A box is the problem. I just mailed mine in to Van's last week for the exact same problem. I'm still waiting to hear back from them on the cost to repair.
 
A builder in Lima Peru fixed his trim by moving the wire from fuselage pin 32 to autopilot pin 17, . . . and moving the wire from fuselage pin 31 to autopilot pin 19, all on the AV-50000A. Read THIS thread.
 
Vans confirmed my diagnosis. My logic board was bad in my AV50001A box. This is a new box so Vans replaced the board and is shipping it back. Ill soon be back in the air. :D
 
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