PT20J

Given this description, I take it this was a new installation using used equipment? Probably best to have the installer figure it out, especially if it sold you the equipment.

Do you have two comm radios? Does it do this on both? Could be a bad radio. If it is a modern audio panel with built in intercom, it will have a failsafe feature to connect the headset directly to comm 1 when it is powered down. Pull the breaker and see if it affects anything. Would help if you could tell us what radios and audio panel/intercom you have.

A lot of us with LED landing and taxi lights (that’s four bulbs on my plane) leave them on continuously. They still draw the most current of anything on the airplane so my procedure is to turn the lights off and leave everything else alone if I have an alternator failure. Pitot heat is also a big current draw and a consideration if you fly in icing conditions.

My speed brake button is on the yoke and easy to brush against if reaching around the yoke with my left hand for the left knob on the G3X. After accidentally deploying the brakes in icing once and immediately retracting and finding that one did not retract fully, I put a red ring on the speed brake breaker and pull it whenever I turn on pitot heat.

There are schematics for the annunciator panel in the M20J Service Manual. IAI, the OEM for the annunciator, still services them and you could ask them for troubleshooting advice: https://www.internationalavionics.com/

Any maintenance technician should be able to fabricate one of those. The dimensions are not critical - it just needs to cover the hole in the air box.

Small ones are 2700 Camlocs; Large ones are 4002 Camlocs. You can get them at Aircraft Spruce and other suppliers. The studs come in different lengths. There is a number on the head that denotes the length. Look at one adjacent to the missing one for the correct number. The 2700 studs are held by a split washer inside the cowling. The 4002 studs need a special pliers to install and remove easily. All these parts are available from Spruce. Skybolt is an alternate supplier and their studs are compatible with Camlock sockets. If you have an enlarged hole in the upper cowling, Skybolt has a 2700-compatible stud with a larger flange that won't fall through the hole.

That looks like a 100 series from the picture. These are pretty simple. Since the brakes have been recently serviced, it's probably the switch or the relay. 100 SERIES SCHEMATIC WIRING.pdf

MTBF?

USAIG, M20J, $250K hull, $1MM smooth, $4490. The real issues seem to me to be too many hull losses - especially gear ups, shop rates increasing due to a critical shortage of mechanics, and parts prices greatly increasing for a variety of reasons.

I believe Raychem invented the solder sleeve. We used them on space-qualified high-reliability equipment in the 1970s. Part of the secret is that that amount of solder is controlled and encapsulated in the sleeves so it does not wick beyond the sleeve which provides strain relief. Properly installed, they are very reliable.

Under federal law, it is a felony to willfully damage or destroy aircraft. 18 U.S.C. § 32.

Check the ignition switch end. If it’s grounded there, you don’t need to ground it at the mag end. In fact, shields are usually only grounded at one end so that no current can flow if the two ends are not at the same potential. Slick recommends grounding at the ignition switch, I believe.

When this happened to mine, it was intermittent and turned out to be a bad connection between board in the computer. Probably @Jake@BevanAviation will have some things for you to try to isolate it.

No, it just took me three tries to learn how to do it. I've never tried RTV 108 on the door seal. I'm a little leery of the two part industrial stuff Guy supplies with his silicone seals because I'm afraid I might never get it off if a seal got damaged. He sent me some of that with a silicone anti-chafe seal for the cowling but I chickened out and glued it down with RTV 108.

The electric system is more complicated, so I would expect it to have more issues. But, mechanically, it is very similar and the emergency gear extension system will protect you from electrical failures. If everyone had upgraded to the 40:1 gears in the Dukes and lubricated them properly, the actuators would probably outlast the airframe. Similarly, the Eaton noback springs are really a non-issue as far as I can tell. So, that leaves the Plessey actuators. There have been several documented failures. It is known only to Mooney how many of these actuators were installed, but my guess is not many which would make the failure rate higher, and you cannot get parts for them. Some will say you cannot get parts for Dukes or Eatons either, but at least Eaton is still in business making it a possibility.

Many people use too much glue.

There are two relays: one turns the motor on one way to retract the gear and the other turns the motor on in the opposite direction to lower the gear. If the relay coil is shorted (or the flyback diode) it would pop the Gear Cont CB (not the Gear Act CB) which is why I asked which breaker popped.

None. Which is really the point. The number of gear up landings caused by mechanical failures (J-bar or electric) is very small compared to pilot errors. Just like driving, the nut behind the wheel is the most likely component to fail. I don't worry about the gear failing to come down (although since I had a relay and then a microswitch fail, I have some concern about it going up); but I do very much worry about getting distracted by unusual ATC requests, traffic or some unrelated emergency.

I used to instruct at a club that had a M20C with manual gear. Over a period of about fifteen years, it landed gear up three times.

Which breaker popped? If it was the gear actuator breaker, it sure sounds like the emergency gear extension system became engaged. I would check the rigging. It's unlikely to be electrical unless the wiring has a short, but you said that the actuator was "locked up" which would not indicate an electrical problem.

Sounds like you did this with the airplane on jacks and the belly opened so that you could watch the jackscrew. If the jackscrew stops, of course the gear will stop retracting. There is not, to my knowledge, a slip clutch in the actuator, and the fact that there is also a problem with cranking the gear down manually leads me to think that something is stripped, especially if the gear stops moving but the motor keeps turning. If it's happening at the same point retracting with the actuator and extending with the crank, I might look closely at the jack screw for a damaged spot.

During prepurchase the airplane will be opened up. Witness or have the inspector take pictures of the actuator including the ID plates. Examine the logbooks for what's been done to the actuator: Dukes: 40:1 gear installed? Periodic lubrication, AD compliance?; Eaton: noback spring replacement; Plessey, well, I wouldn't buy it with a Plessey personally.

Another option https://www.aircraftspruce.com/catalog/topages/pointers.php

3M Dual Lock has much stronger adhesive.