Gear doors won't close on ground...

[stackj]

Bandit,

I do not have diagrams for your particular model, however all the diagrams for the models I do have indicate that the gear door circuit works as follows:

28 VDC Power from the circuit breaker goes to the Nose Gear downlock switch, then to the Right Main Gear downlock switch and then to the Left Main Gear downlock switch. The output from the Left Main Gear switch is fed both to the Green Light and the Gear Door Up/Down switch.

Your indication that the green light does not turn on indicates that the circuit has failed somewhere between the circuit breaker and the Gear Down (green) light.

You should be able to trace power by turning on the battery switch while on the ground and testing for 28 volts at each of those switches (both sides of each switch).

The circuit diagrams on later model aircraft appear to have some connectors in the circuits in the vicinity of the main gear. The parts list I have defines them as "housings", but the diagram uses a connector symbol. You may want to look for these. If they are connectors any one of those could cause the problem.

It is also possible that a switch just isn't quite in the right position to close when the gear is in the locked down position even though the switch is electrically good. The voltage checks defined above would also reveal this problem.

Good Luck!

[Dale Campbell]

I just replaced my 2 Main gear down lock switches. They gave me a lot of problems with intermittent gear doors failing to close. I checked the resistance with a meter across both switches and found the resistance to be about 100 ohms when it should be zero. I think the inside of these little mico switches get very dirty and the contact resistance goes up until they fail. After changing these 2 switches all my gear failure problems disapeared. Dale