brianucsf

I finally got a chance to dig into this a bit further today. I did some troubleshooting suggested by Jake and found: 1) The harness from the computer out at the roll servo is sending out expected readings across the D and L pins. When the autopilot is held on and heading bug is turned in one direction the voltage is positive, in the other negative, and when my 11 year old son centered the heading bug as well as he could, it ended up close to zero. ALso, the FD bars on the Aspen showed the expected banks. From all that I assume that the computer is working well, and the problem is the roll servo. 2) I cleaned the contacts on the main connector between the servo and the computer, to no avail. The ground from the servo looked a bit suspect, so I cleaned that as well, and again, it didn't fix the issue. 3) When the radio master is turned on (but not the autopilot) there is a whirring noise from the servo but the cable doesn't turn. It sounded like a fan, but I don't know if there is a fan in that unit. 4) In the past, when holding the autopilot in the up on position, it would show the FD correctly for the heading bug location, but would actually pull the ailerons full left. Once I cleaned and reassembled, the servo would move perhaps 1/8 turn and seem to sort of stall. Once it stalled, even if I had my son rotate the heading bug, it didn't really move. 5) I'm not sure if I have a KS178 or KS201 roll servo. I tried to remove the two bolts closest to the access panel, but the servo unit didn't want to come out after that. I was afraid I would somehow mess up the aileron control, so I didn't keep experimenting. I've attached a few pictures showing the bracket. So my questions are: 1) Do you agree that it sounds like the roll servo needs to be removed and serviced/replaced? 2) Do you know of a instruction manual explaining how to remove whichever roll servo I have (or, is it tricky enough that it is best left to the professionals)? Thanks so much for your advice. Brian

Thanks for all the helpful feedback. I will try to reseat the connections later this week and then proceed from there.

I purchased a 1980 M20J six months ago with a KFC200 controlled by an Aspen EFD1000 via an EA100. Twice over that time I had the autopilot fail to engage (switch wouldn't stay up and AP light blinked) but after a few minutes of hand flying if I tried again it would behave properly. A few flights ago, however, the autopilot wouldn't engage and hasn't done so since then. If I push and hold the test button when on the ground, all lights go on except the trim light never turns on nor do I hear a tone. However, I hadn't ever used the test button before (I just ground tested by moving the heading bug and pitch rocker) so I wasn't sure what to expect on my unit. After reading about the potential flaky switch latch mechanism, I tried a ground test by holding the switch in the on position and moving the heading bug - the yoke moved in the expected direction so I thought perhaps a faulty switch was the problem. While flying, I held the switch in the on position with a rubber band and it flew like it was on rails for at least 10-20 minutes with both GPSS heading and altitude locked in. Suddenly, however, it started making a left bank (when the FD display was showing straight and level). I shut it off and tried one more time in heading mode (holding the switch in the on position since it wouldn't latch there), but it continued to want to bank left even when the heading bug was directing a right turn or level flight. Any thoughts on what the problem may be? I'm handy enough with troubleshooting and a multimeter, but I'm by no means an A&P or avionics guy. Is there additional troubleshooting I could do to help narrow down the issue? One final note, which I think is unrelated, is that occasionally two hours or so into flights the EA100 system will glitch, I will receive an aural alert to "Check EFIS", and the autopilot will kick off. Thanks to the wisdom of MooneySpace, I now know to pop the EA100 breaker, wait a few seconds, reset it, and a minute or so later everything would work like a charm. This seems like a completely different issue (which I can manage with the circuit breaker trick) but wanted to mention it in case it was important. Thanks in advance for any assistance.

PT20J, Beard, and M20F-1968 were spot on. The speed brakes must have gotten bumped and deployed. One of them doesn't appear to full retract every time, so the circuit breaker is pulled so as to not have another accidental deployment until I get that sorted out. Beard, the brakes are there because there were put in by a previous owner. Thanks to you all.

PT20J, that makes a lot of sense. I will see if I can repeat the sound with that process.

ArtVandelay, thanks, I will check for the sound without engine start up today or tomorrow. LANCESCASPER, yes, the speed brakes are electric.

I have a very new to me 1980 M20J. When I shut it off at the self serve fuel pump yesterday, right as I switched off the master, there was a fairly loud clunk sound. It almost sounded like the clunk/thud when the gears lock in place and it seemed as if I even felt a bit of a shock/vibration when it happend. I hadn't heard that sound before, but when I then fired it up again, taxied to the tie down, and shut it down again, there was the clunk again (maybe even two in rapid succession). I've only shut this particular plane down a half a dozen times before that (which were all uneventful), and I've been in a few other M20Js and I have never experienced this sort of clunk. Any thoughts about what might be the issue? For what it is worth, the plane has speed brakes, but the pre-buy suggested there might be issues with retraction of one of them, so I haven't touched them yet. Also, the vacuum system has been removed from this plane. PS I have learned a huge amount from MooneySpace as I have lurked and looked for my plane - I've joined and donated now but thanks to all who have contributed a great deal of knowledge to this site.