Is there a preferred method/cleaner to clean switches in the landing gear?

[cowman]

I've had intermittent issues with my nosewheel gear down switch not working. A couple of years back an A&P fixed it by "cleaning it" which I assumed was spraying something like contact cleaner into the switch. I'd like to try that myself, what's the best miracle chemical in a can to spray into it? I've used stuff like deoxit before just not on an airplane.

 

[Daleandee]

I can't speak specifically to a landing gear switch but I've used Deoxit (Gold G-5) for contacts in recording equipment, switches on my motorcycle & automobiles. I'm quite amazed at how well it has worked. It is a bit costly but IMHO it has been worth it.

Deoxit from Amazon

Perhaps you could ask your A&P about it. @Bell206 or @Dan Thomas may be along shortly with the right answer ...

 

[Bell206]

I've had intermittent issues with my nosewheel gear down switch not working.

What model and year aircraft?

 

[cowman]

What model and year aircraft?

76 Piper Lance

 

[Dan Thomas]

I have cleaned microswitches by immersing them in non-chlorinated brake cleaner and working the action, then blowing the cleaner out with compressed air. Do that several times. Do this with the switch removed from the airplane. Doing it while installed is mostly a waste of time.

But the only time that makes sense is when a new microswitch is not available. They aren't expensive, usually. Of course, some OEMs are famous for using some non-standard, rare and expensive stuff instead of common industrial components when they could have.

And watch to see how the mechanic is lubricating things near that switch. Some are convinced that if a little lube is good, a lot is much better, and the surplus gets into switches and other places where it causes trouble. Lube that is not right inside the moving stuff, against the bearing surfaces, is useless. Cessna flap actuators are the classic mess as mechanics hose oil or grease at them, and the limit switches get loaded with it and quit working. An up-limit switch that fails will not let the flaps retract, and in an overshoot that can get deadly if the conditions are right.

 

[Ed Haywood]

CRC electrical parts cleaner seems like a good place to start. 10 bucks at Walmart.

 

[Bell206]

76 Piper Lance

I don't believe you'll have much luck with those type switches as they're sealed and use a tab vs roller. Pic below of the switch for reference. They're cheap also. Since its an intermittent problem I would be more inclined you have some play in the down mechanism as you're only dealing with less than .090" clearances. If you still want to "clean" them I don't think it would hurt anything, however, you will want to make sure to relube any part that requires it in case you wash more than the switch. I've only used Misty and CRC contact cleaner so can't comment on the other types.

 

[cowman]

I don't believe you'll have much luck with those type switches as they're sealed and use a tab vs roller. Pic below of the switch for reference. They're cheap also. Since its an intermittent problem I would be more inclined you have some play in the down mechanism as you're only dealing with less than .090" clearances. If you still want to "clean" them I don't think it would hurt anything, however, you will want to make sure to relube any part that requires it in case you wash more than the switch. I've only used Misty and CRC contact cleaner so can't comment on the other types.

View attachment 136016

Good to know, I'll see about new switches next annual.

What is specifically going on is a few years ago I noticed on colder days my nose down indicator would seem to take a long time to come on when I'd put the gear down. At the next annual I discussed with the A&P and sure enough during the gear swing test the nose wheel light didn't come on. He diagnosed it as a 'dirty switch' and sprayed it with some sort of cleaner and the symptoms went away. His theory was that in flight the vibrations were essentially vibrating the dirty switch into making contact. That was a few years back, recently I've had a couple of times when I've initially turned on the master to start the airplane and the nose gear down light was off. As soon as the engine starts up the light comes on and everything functions normally.

I also had one incident that has not repeated where I put the gear up after takeoff and the gear unsafe horn sounded. Cycling the gear made it stop and it hasn't happened again. A lot of people on the PA-32 group on FB were saying the up limit switches can cause that problem. This also happened on a cold day, not sure if that's relevant. I did notice some grease buildup around a couple of them so a good cleaning of all those little micro-switches seemed like a reasonable thing to do. There's no evidence of any oil leaks or physical problems one can see from crawling under the parked aircraft and looking around.

 

[Dan Thomas]

That was a few years back, recently I've had a couple of times when I've initially turned on the master to start the airplane and the nose gear down light was off. As soon as the engine starts up the light comes on and everything functions normally.

Vibration shaking the contacts enough to get them contacting.

He diagnosed it as a 'dirty switch' and sprayed it with some sort of cleaner and the symptoms went away.

The switch needs washing out, not just spraying. There is grease inside it. It needs to come off and be immersed and blown out. Even then, the contacts might have grease baked onto them by the arcing of the switch and would need replacing anyway.

Now, if it is sealed like Bell says, you need a new switch. And if it is sealed, grease or oil shouldn't be able to get in there at all. But I have seen some sealed-looking switches that were just microswitches inside a housing that isn't sealed at all. It's just a bit of armor to protect the switch from flying debris.

 

[AV8R_87]

Deoxit (Gold G-5)

That - if you can get it to the contacts.

One thing that causes problems is too little current. You see switches rated for amps/tens of amps used in circuits where only fractions of an amp pass through them. Without the cleaning action of a high current passing through them, they can build up a layer of dirt that will cause intermittent issues.