Nav Lights and Landing Light Switches

[Toothdok50]

Just purchased a '63 M20C and on the ferry flight for delivery, pilot reported that after a few minutes of operation the switches for both the navigation lights and the landing light flick off.  Navigation lights were on for much longer before having the switch tripped.

Is this likely an overload/short?  Are there breakers built within these switches?  Is it a sign of aging switches?

Anyone have insight to this problem?  Leads on replacement switches anyone?

Any help would be great guys...  Seems like an an overload situation and not an actual short, or a faulty breaker--if there is in fact one built into the switch itself.  Looking for info on these vintage switches before I consult an A&P on the issue.  Maybe its the excuse I need to update the lighting.

[Guitarmaster]

If it was a short, it would trip immediately. It sounds like the switches / breakers are getting tired. This problem is fairly common in the older planes. in addition, if your landing light switch is next to your nav light switch, it may be producing heat which can cause both trip. Keep in mind, that incandescent landing light is pulling 18 amps. . And your navlights are pulling 7.5.
The first thing I would do is switch out your landing light to an LED and do the same with your nav lights. There are a few manufacturers who make LED nav lights that are direct replacements for the bayonet bulbs. Check out Aerolites.
This will reduce the load on your system dramatically.


Sent from my Pixel 2 XL using Tapatalk

[GLJA]

1 hour ago, Guitarmaster said:

If it was a short, it would trip immediately. It sounds like the switches / breakers are getting tired. This problem is fairly common in the older planes. in addition, if your landing light switch is next to your nav light switch, it may be producing heat which can cause both trip. Keep in mind, that incandescent landing light is pulling 18 amps. . And your navlights are pulling 7.5.
The first thing I would do is switch out your landing light to an LED and do the same with your nav lights. There are a few manufacturers who make LED nav lights that are direct replacements for the bayonet bulbs. Check out Aerolites.
This will reduce the load on your system dramatically.


Sent from my Pixel 2 XL using Tapatalk
 

This. 

My 74F had the same issue. Night flights would cause the switches (NAV, Landing and the odd time belly strobe) from time to time. They would be able to be reset after a short cooling period. 

I switched out the landing, belly strobe and NAV to LED at last annual. They haven’t tripped since. 

[Toothdok50]

Thanks guys...suspected this would be a good fix (going with LED) and have already been looking at replacement options.  Didn't realized these switches were able to trip  due to heat.

Knowing LED's pull so much less current, my first thought was going that route.  Now settling the question as to whether a LED replacement is a minor alteration that needs A&P sign off or if its just a PPL action with a log-book entry is the question.  Viewed countless posts on this topic and seems like its splint down the middle as to how such a change is handled.  UGH!

[kpaul]

32 minutes ago, Toothdok50 said:

Didn't realized these switches were able to trip  due to heat.

The switch is also the circuit breaker for the lights.

[carusoam]

3 hours ago, Toothdok50 said:

Thanks guys...suspected this would be a good fix (going with LED) and have already been looking at replacement options.  Didn't realized these switches were able to trip  due to heat.

Knowing LED's pull so much less current, my first thought was going that route.  Now settling the question as to whether a LED replacement is a minor alteration that needs A&P sign off or if its just a PPL action with a log-book entry is the question.  Viewed countless posts on this topic and seems like its splint down the middle as to how such a change is handled.  UGH!

The circuit breakers are designed to trip based on heat.  Not that heat does it accidently.... but a hot day doesn’t help either...

The CBs Do wear out. Generate more heat, and mostly mechanically trip easier... compare a new CB/switch to an old one... the new one clicks in position, the old one doesn’t click... the click keeps If from tripping easily...

Replacing the lights with LEDs fixes something other than the root cause.

Consider replacing the CBs with the proper size for the new LED lights....

The old CBs are misbehaving compared to their original design... a hint that it is time to replace them...

Of course... There are people that need to squeak everything they can out of their aviation budget...

We have been named CBs because we held onto the old worn out stuff longer than we should have.....  CB= Cheap Bas...

 

The landing light uses a lot of power, gets used often, wears and is easily bumped by the moving panel above...

If your lights go out after a bump from turbulence... this is probably why it happens...

Replacing CBs is pretty easy... got a mechanic to work with?

There are many things that we can do for ourselves as PPs... but, when it comes to logging the work properly for one-off upgrades... it might be best to work with that mechanic...

Working on a simple project like oil change is a great way to work with a new 2U mechanic...

Then tackle the more complex LED light issue...   some people get to the level of doing a lot of their own maintenance with less and less oversight... there is always going to be some things a mechanic needs to do...

Best regards,

-a-

 

[N201MKTurbo]

The circuit breakers have a bimetallic dome in them. The switch is spring loaded to the off position. When you turn it on a bump on the switch lever snaps into a hole on the dome. The current passes through the dome and when it gets hot it releases pressure on the bump and lets the switch spring back to off. 

They ware out because the bump on the switch lever looses its edges and slips out of the hole easier. 

[S.C.]

Great topic!  I was going to ask a similar question.  

I’ve been working with my A&P and been trying to identify the source of the heat.  I can feel the bus getting warmer and tripping the nav lights.  First step was to replace the switch.  Having done that and having the problem recur, it makes sense to go for the LED lights.  One of the other comments my mechanic made was “old electrical is tough, it works fine for years, but unlike a tire, it’s not always easy to see the immediate problem”. 

Isolating and trouble shooting takes time and patience.  

I have a 65 C, any suggestions for good (reasonably priced) LED replacement bulbs for nav and landing?

[jaylw314]

20 hours ago, Toothdok50 said:

Thanks guys...suspected this would be a good fix (going with LED) and have already been looking at replacement options.  Didn't realized these switches were able to trip  due to heat.

Knowing LED's pull so much less current, my first thought was going that route.  Now settling the question as to whether a LED replacement is a minor alteration that needs A&P sign off or if its just a PPL action with a log-book entry is the question.  Viewed countless posts on this topic and seems like its splint down the middle as to how such a change is handled.  UGH!

The LED nav lights (the legal ones, anyway) are TSO'd for the FAA lighting requirements.  As such, it is appropriate for those to be replaced by the owner under preventative maintenance, since replacement of an item with an equally TSO'd item is generally not considered a modification, and replacement of position and anticollision lights is considered preventative maintenance.

Landing lights, on the other hand, are a grey area.  They are allowed to be replaced by owner under preventative maintenance, but landing lights have no TSO.  So technically, the only thing that would be legal would be to replace it with EXACTLY the same item, which makes no sense.  Hence the controversy.

[rbridges]

21 hours ago, Toothdok50 said:

Thanks guys...suspected this would be a good fix (going with LED) and have already been looking at replacement options.  Didn't realized these switches were able to trip  due to heat.

Knowing LED's pull so much less current, my first thought was going that route.  Now settling the question as to whether a LED replacement is a minor alteration that needs A&P sign off or if its just a PPL action with a log-book entry is the question.  Viewed countless posts on this topic and seems like its splint down the middle as to how such a change is handled.  UGH!

Changing the landing light is a no brainer.  I changed mine to LED after two months of ownership.  The incandescent bulb blew on me at night.  After the second time, I said screw it and bought an LED.  I fly with it on nearly 100% of the time.  I eventually got the whelen wingtip LEDs.  I had my IA help me just because I didn't want to mess with the splicing.  It was pretty easy overall, but I didn't connect the sync wire from left to right.

[Hank]

2 hours ago, S.C. said:

I have a 65 C, any suggestions for good (reasonably priced) LED replacement bulbs for nav and landing?

We fly certified planes, there is nothing "cheap" or "reasonably priced" that fits them . . .

Whelen makes good LED landing lights; I like mine. They're just over $400. I don't have LED position lights yet, because they're too pricey. I have noticed that prices are coming down on the, to about $470 each, and the $40-$50 surcharge for the green light seems to have gone away. So I'm continuing to wait on those, because my old ones keep working.

[rrbeck11]

New question: I have a short in my wiring to the right (green) wingtip nav light.  I have disconnected the wire from the Nav Light switch and removed the green bulb, and it's fixture to confirm the short to ground.  Does anyone know where the 9-pin amphenol connector (on the left in the schematic below) is located?  From the schematic, it appear to be in or near the wing root, or perhaps near the copilot's right knee.  Before I remove interior or exterior panels, I'd like to go to school on MS collective knowledge.  Thanks!

 

Randy

 

 

Edited June 1, 2020 by rrbeck11
updated schematic clip