[billsheila]

I had a very similar issue on my 1965 and spoke about it already on this forum and on the CPA website where Tom Carr was most helpful in getting to the bottom of it. In my case it turned out to indeed be adjustment of the main gear switches, as was already suggested in this thread. The issue would arise in flight but not on jacks, making it that much harder for my A&P to diagnose. As I recall him explaining it, there is a certain amount of play in the main gear when they are in the lock saddles and when system pressure and wind would fluctuate, we were getting intermittent contact in one of the main switches. It would make contact properly when first actuated, also make contact properly when relaxed in the saddle, but if you pushed up hard on the gear leg (when up and locked and on jacks) it would lose contact. Once the gear were up and locked in the saddles if this would happen the only thing would happen is that the door solenoid would de-energize sending fluid from the pack to the door circuit, opening the doors. The switch needs to be adjusted on its bracket such that it maintains contact when first actuated, when relaxed in the saddle and finally when pushed upward as hard as you can by hand (to simulate wind and system pressure changes). Not sure if this is your issue, but it certainly was in my case.

I also totally agree with the suggestion in this thread to keep the whole affair clean and properly lubed. The other suggestion (which my A&P did throughout my process was to solder the crimped wire connections on the switch wires). I am not sure if this is standard good A&P practice or what but my wires had at some point had new terminals put on, but they were not soldered and my A&P said that with something as critical as gear (and where vibration and the elements can get at the terminal) he solders the crimp.

I had exactly your issue where it was intermittent at first, and if I cycled the gear it would usually correct itself, but it got worse with time and I got it corrected at annual.