170A Tail Light Problem

[Onewinglo]

Guys I'm doing a little troubleshooting on my 170A and I need a some guidance.
The tail light is not working. It had a 1156 lamp installed so I bought a new one which did not fix the problem. The continuity of both the old and new 1156 lamps is good. I get 12 VDC at the lamp socket but the socket has two terminals but only one wire. Obviously I connect the ground lead of my multimeter to the airframe in order to see 12 VDC. Is this system designed to get its ground through the airframe or am I missing a wire?
Thanks, JP

[GAHorn]

Wrong socket....or wrong bulb.

I suspect you have the wrong socket if it has two contacts inside for the lamp.

[Onewinglo]

I suspect you have the wrong socket if it has two contacts inside for the lamp.
Wrong socket....or wrong bulb.

Thanks for the reply.
This lamp socket has two terminals on the bottom for leads, (12 VDC and Ground) but only one contact on the inside of the socket (12VDC) for a single element lamp, such as the 1156. I bought a pair of GE-93 lamps to try friday. I tried to jumper a ground to the lamp socket but it still did not work. Ill work with it again Friday.
JP

[KS170A]

Thanks for the reply.
This lamp socket has two terminals on the bottom for leads, (12 VDC and Ground) but only one contact on the inside of the socket (12VDC) for a single element lamp, such as the 1156. I bought a pair of GE-93 lamps to try friday. I tried to jumper a ground to the lamp socket but it still did not work. Ill work with it again Friday.
JP

Where were you trying to jumper to ground (i.e. rudder skin)? Could be there is not a good ground continuity between rudder and airframe. If you're getting 12v to the socket, and the socket is good, just about has to be a ground between the rudder and airframe.

[Onewinglo]

Josh, I think you'er right. I'll try to jumper a ground from the airframe and see what happens.
JP

[GAHorn]

The problem is the socket versus the lamp choice.
The GE 93 (specified) is a single-contact lamp, as is the 1156 (both are automotive and will work just fine in the correct lamp socket.)
Oherwise you need to obtain a dual-contact, single-element lamp.

[Onewinglo]

I think I see my problem. My lamp socket is the same type as pictured below but my socket has only one lead. The lead that grounds the socket is missing.

Picture%2010368-20141031-172439.jpg

[KS170A]

I converted all my position lights to LED units. I recall having to find a place to attach the ground wire, leading me to think my original socket also only had one wire but functioned correctly. But, that has been a few years and a few beers ago, so my memory may be faltering... Seems like the socket assembly should ground via the attachment screws, but then that depends on continuity through the socket, bezel, and screws...lots of room for gremlins. A dedicated ground wire will likely help.

[Joe Moilanen]

The ground would also have to have continuity through the rudder bearings or rudder cables, not the best. I remember replacing my entire wire to the light years ago though, and don't remember two wires either

[Onewinglo]

Josh, I would like to convert my Nav lights to LEDs also. Do you recall which lamps you bought, or where you bought them?
Thanks, JP

[170C]

Do a search on the forum regarding which bulbs and sources. George Horn has several posts on the subject.