Insconsistent Gear Indicator Bulb/Socket

[Kevin Weidner]

The past 6 flights or so in our Twin, the green gear down indicator light has been acting up. About half the time, it will come on normally. The rest of the time, we had to tap on the bulb or turn it a bit to get it on. The last flight, I had to screw it out 2 turns and back in to get it on, and I am not going to fly it again until it works properly. Since then, I have spent about 2 hours fiddling with it to no avail. I took the knife connectors on both the positive and ground wires apart and cleaned them with contact cleaner. Also put plenty of contact cleaner in the socket and cleaned with a rag. After all of the times in and out with the bulb, I would have to say there is no change to the consistently inconsistent nature of the problem.

Is there any source of a new socket, or should I look for a good used one? Webco doesn't have them and didn't know of anyone that does.

Thanks in advance for any help

[N3322G]

Ah Kevin,

I have seen this twice before in our Twin (43 years of being around it). Of course this may not be your problem but it sure sounds familiar.

1st time we fought it for three years before we called Maurice Taylor. It was an intermittent problem - would never fail with mechanic on board. One night we had the problem and turned the panel light rheostat to check to make sure that wasn't the problem and ta-da gear light. We used that trick for awhile, changed the gear wiring harness and then called Maurice who said, check the nose gear micro-switch for correct adjustment. I wasn't interested in adjustment, I bought a new micro-switch ($25 at the time) and gear worked perfectly for 15 years or so.

2nd time the green gear light was intermittently slow - sometimes came on in the normal 6 seconds and sometimes it took 2 minutes. So I figure it had to be the other micro-switches - changed them and problem remained, changed the nose gear and ta-da gear light came on in 6 seconds just like it had for most of its life.

Let me caution you though - if this turns out to be your problem be absolutely so that the mechanic follows every single service manual step in the micro-switch adjustment process. It is iterative and takes patience and at the end, you should use Maurice Taylor's pre-flight video steps to check the gear. I made the mistake of trusting a highly experienced Comanche mechanic. He was in a hurry and the result was a few landings later the gear collapsed due to badly adjusted gear micro-switches. We had the green gear light as a false positive, landed and the gear folded. This bad-adjustment was verified by 3 independent sources. It has taken years to get the Twin back to close to where it was ... so learn from my failure to 'trust but verify' in this instance.

Hope this helps.

P.S. Original colors for N3322G, formerly known as N8855Y (for 1 year), were white with black and yellow.

[Kristin Winter]

I had a slow green light a number of years ago. Turning the rheostat/instrument light switch on and off brought the green on. The problem as the same as Pat had. The nose gear microswitch was going bad and the changing the voltage seemed to shock it into behaving, temporarily. I would recommend replacing the nose gear microswitch. If the wiring is original, I would recommend getting the kit from Comanche Gear and replacing the entire landing gear harness and having the system rigged. I would also recommend having someone who knows Comanches very well do this. For first timers it is a 10-12 hour job. It is 6-7 hours for an experience mechanic.

[Kristin Winter]

I had a slow green light a number of years ago. Turning the rheostat/instrument light switch on and off brought the green on. The problem as the same as Pat had. The nose gear microswitch was going bad and the changing the voltage seemed to shock it into behaving, temporarily. I would recommend replacing the nose gear microswitch. If the wiring is original, I would recommend getting the kit from Comanche Gear and replacing the entire landing gear harness and having the system rigged. I would also recommend having someone who knows Comanches very well do this. For first timers it is a 10-12 hour job. It is 6-7 hours for an experience mechanic.

[Richard L Doehring]

I have seen the "slow to glow" geen light several times on more Comanches than I can to admitt including my 260B. For years I replaced sections of wires, cleaned switches and did exactly what Kristin did, switch the nave lights on and off, and continued doewn the road. A couple of years ago I decided to yank out all the wires and replace them with Matt's (Comance Gear) new wiring harness. The problem has never presented itself again and I too suspect the nose gear swithch or wires to the cannon plug were the culprit.

Richard Doehring

[Kevin Weidner]

Thanks for all the tips! I think we're going to replace them with the push-to-test kit as mentioned if I can't get it to work any better. That way there should never have to be any more swapping bulbs in flight. I can't say that it has ever been slow to light, but this problem has made it not come on at all sometimes, and it took some wiggling of the bulb for a while to get it lit.