Gear doors won't close on ground...

[skymstr02]

The same thing happened on my O-2A, and it turned out to be the microswitch on the powerpack that controls the solenoid. The switch mimics the solenoid troubleshooting, and this particular switch is not called out in the airframe wiring manuals, but is in the illustrated parts listing.

[atsiii]

Thanks Skymstr02! Back in 1999, that same micro-switch had to be replaced on the '69 I was flying then, so I was suspect of it. It's a 3-wire switch but I can't find a diagram to know what each wire should be. I still have the '69 as a parts plane, so maybe I should just change it...

[skymstr02]

I just bought the switch from Yingling for $30, they had it in stock. There are actually four terminals to this switch, and the actuator button is in the center, which makes this unique. Two of the terminals are wired together so this makes this a single pole, double throw microswitch.

Take the white plastic drain tray off from under the powerpack, and you will see it towards your instrument panel. There are three wires going to a terminal board on the bottom of the powerpack, so you can take the switch and wires off as a unit.

[stackj]

I am attaching a scanned diagram given to me by a friend. This looks like part of a text from some mechanics school who teaches Skymaster systems, but I can't find any reference on this package to either ask permission or credit them. Anyway, I'm chancing making this available because it is a much simplified diagram of the gear door permissive systems... Here it is. When you zoom in on the picture the text is more readable.

The Key to remember. If power is off at the Landing Gear Door Solenoid and Hydraulic pressure is applied, the doors will open.
If power is on at the same solenoid and hydraulic pressure is applied, the doors will close.

[atsiii]

Thank you, Jim & Skymstr02!