Intermittent nav lights

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Matt C

Pre-takeoff checklist
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Matt C
Hi all. My '66 172 has malfunctioning wingtip lights. I took the bulbs out and tested the sockets. I get a steady light on the probe. When I push the bulb back in, it will light as I'm pushing it in but then goes out as I spin it into place. The grounds are intact and the wires appear sound. Both sides are doing the same thing. I'm assuming cleaning the contact surfaces will help, but what I'm wondering about from the experts is weather or not dielectric grease in the socket is a good idea to aid contact and corrosion issues. Thanks in advance.
 
Have you ruled out broken leads or a grounding issue?

And DG is fine in the socket.
 
My first guess is a bad ground....

I've not used the grease but if you do go light to prevent shorts.
 
Normally one would wish to avoid dielectric grease on contacts.
 
That's pretty common with old aircraft, you may have luck with cleaning up the contacts, it could be temporary, but really the sockets need replaced.
 
GlennAB1 said:
That's pretty common with old aircraft, you may have luck with cleaning up the contacts, it could be temporary, but really the sockets need replaced.
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I suspect you're right. I haven't been able to locate them yet. WagAero or AircraftSpruce probably have some hiding somewhere.

Other suppliers would be appreciated.

Thanks all.
 
The sockets and the contact get oxidized. Scrape the contact button with a small screwriver, and pick, with a dental pick or similar, at the two small grooves that the bulb pins lock into. The contact button is solder, and the lead in the solder can look good but be covered with lead oxide. That goes for the bulb's base, too. The brass socket's oxidation is also a very poor conductor.

It takes years to oxidize. I wouldn't bother with DC-4 unless the electrical stuff is constantly wet from fog or something.

The ground connection at the outboard wing rib is another place to find trouble, as is the other end of that wire where it's connected to a ground ring that is captured by the knurled nut on the inboard end of the socket. Things get dirty in there, too.
 
Checkout_my_Six said:
My first guess is a bad ground....

I've not used the grease but if you do go light to prevent shorts.
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You say to prevent shorts... why do you think dielectric grease will produce a short? Just curious about your reasoning. Dielectric grease is an insulator, not a conductor. It will help to prevent oxidation of the metals where the contacts have poor contact. Are you thinking it will attract metal shavings or something?
 
Plain old ordinary white grease does a good job of corrosion prevention. Save the dielectric stuff for the spark plug leads.
 
Dun know....did I say that I never use it?
Joshuajayg said:
You say to prevent shorts... why do you think dielectric grease will produce a short? Just curious about your reasoning. Dielectric grease is an insulator, not a conductor. It will help to prevent oxidation of the metals where the contacts have poor contact. Are you thinking it will attract metal shavings or something?[/QUOTE
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Checkout_my_Six said:
Dun know....did I say that I never use it?
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Yes. But you warned against using much. I thought you may know something I didn't. I used to think it was a conductor many moons ago and would have said the same thing but was corrected by someone who knew more than me. Never know what I may learn.
 
Dan Thomas said:
The sockets and the contact get oxidized. Scrape the contact button with a small screwriver, and pick, with a dental pick or similar, at the two small grooves that the bulb pins lock into. The contact button is solder, and the lead in the solder can look good but be covered with lead oxide.
Click to expand...

And since lead oxide (more commonly called lead dioxide) is used as the positive plate of a battery why would you worry about solder (tin and lead) oxidizing? Both tin and lead oxide are conductors.

Jim
 
Joshuajayg said:
Yes. But you warned against using much. I thought you may know something I didn't. I used to think it was a conductor many moons ago and would have said the same thing but was corrected by someone who knew more than me. Never know what I may learn.
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see there.....the gift that keeps on giving. Thank you. :D
 
Joshuajayg said:
You say to prevent shorts... why do you think dielectric grease will produce a short? Just curious about your reasoning. Dielectric grease is an insulator, not a conductor. It will help to prevent oxidation of the metals where the contacts have poor contact. Are you thinking it will attract metal shavings or something?
Click to expand...
Great! Lets slather up all our electrical contacts with it. (insert sarcastic here)
Actually I can understand wanting to use a corrosion preventative, but it does sound counterintuitive; "Here, let's put this non-conductive stuff on our electrical contacts to prevent them from corroding, and thus enhancing the connection."
 
bluerooster said:
Great! Lets slather up all our electrical contacts with it. (insert sarcastic here)
Actually I can understand wanting to use a corrosion preventative, but it does sound counterintuitive; "Here, let's put this non-conductive stuff on our electrical contacts to prevent them from corroding, and thus enhancing the connection."
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I does sound counterintuitive. However, it is the physical contact of the leads, contacts, terminals, etc. that transfer current. The dead space next to that physical contact is where minor amounts of arcing happen which creates the corrosion you don't want. If it is filled in with dielectric grease to keep the oxygen off and enhance insulation, corrosion is less likely to happen.

I would slather all my connections in it but in certain places, it is very helpful.

It won't help conduct current but it will help prevent corrosion.
 
weirdjim said:
And since lead oxide (more commonly called lead dioxide) is used as the positive plate of a battery why would you worry about solder (tin and lead) oxidizing? Both tin and lead oxide are conductors.

Jim
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Whatever the stuff is that forms there, I get light when I clean those contacts off.
 
GlennAB1 said:
Yeah but, because of the dirt and filth, the contacts will become pitted from arcing. I've seen the solder on a bulb completely burned away.
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Agreed, NO solder is a pi$$ poor contact. ANY clean tin-lead solder (oxidized or not) is a perfectly good contact.

Jim
 
Thanks to all for the good discussion. I'm leaning towards cleaning and putting it back together dry and re-checking for corrosion at the next annual or next sign of trouble. If I find new corrosion I'll grease. New strobes or LEDs are very tempting but I think $1000 on this plane could do better things - no shortage of stuff to update :)
 
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