Troubleshooting tail position light

[Guest]

I’m having a hard time with my tail nav light. The old one showed no continuity. I ordered a new one shows 2.3 ohms. I have 12.8 volts at the socket. Thing still won’t work. I tried putting the leads straight to the light and it doesn’t work. This is the same as the part I removed ge 1777. Is there something I am missing. 

[N201MKTurbo]

What do you mean you put the leads straight to the light? Did you hook 12 Volts to the light bulb and it didn't light up?

Most likely you have a high resistance somewhere in your circuit. You need to find that place.

Have you removed the socket and hooked the wires of the socket to 12V? The sockets sometimes wear out, the bump that contact that center of the bulb gets warn away and it won't make contact anymore. You can usually fix that with a little ball of solder on the contact. The other thing is the grounding of the rudder itself. I don't recall if there is a ground wire running back to the airframe, or it is using the rudder as a ground. If it is just using the rudder, I would run a ground back or add or check the ground strap for the rudder.

[Guest]

Thanks. Tested all that. Will try the solder on the ball. 

[Utah20Gflyer]

One time my landing light went out.  I replaced the bulb and still didn’t work.  Started testing lots of things.  Turned out the new bulb was defective.  Wasted a lot of time for nothing.  The lesson is don’t assume new means it works.  I’d try another bulb if you can’t get your hands on one and see what happens.

[Fly Boomer]

1 hour ago, Kerrville said:

I tried putting the leads straight to the light and it doesn’t work. This is the same as the part I removed ge 1777. Is there something I am missing. 

We would like to think that something new or freshly overhauled will perform flawlessly, but both new and overhauled items suffer a lot of infant mortality.  As @Utah20Gflyer suggests, If the voltage at the socket is okay, that only leaves the bulb or the socket itself.

[N201MKTurbo]

15 minutes ago, Fly Boomer said:

We would like to think that something new or freshly overhauled will perform flawlessly, but both new and overhauled items suffer a lot of infant mortality.  As @Utah20Gflyer suggests, If the voltage at the socket is okay, that only leaves the bulb or the socket itself.

Not necessarily. Because most meters have an input impedance greater than 10 mega ohms. It is possible for a meter to read 12 volts at the socket and the socket not able to light the light. There could be a bad connection somewhere that would drop most of the voltage when the bulb was powered up.

[Fly Boomer]

3 hours ago, N201MKTurbo said:

Not necessarily. Because most meters have an input impedance greater than 10 mega ohms. It is possible for a meter to read 12 volts at the socket and the socket not able to light the light. There could be a bad connection somewhere that would drop most of the voltage when the bulb was powered up.

Is that true for so-called "digital" meters?

[N201MKTurbo]

17 minutes ago, Fly Boomer said:

Is that true for so-called "digital" meters?

Yes.

The meter will only draw about 0.0000012 AMPS to measure the voltage at the socket. The bulb will draw about 2 AMPS to light up.

Let’s say there is a bad connection with a resistance of 1000 ohms. The voltage drop with just the meter in the circuit would be 0.0012 volts across the bad connection. With the bulb in the circuit, the voltage drop across the bad connection would be 11.982 volts. This leaves only 0.072 volts for the bulb.

[Fly Boomer]

9 minutes ago, N201MKTurbo said:

Yes.

What kind of meter doesn't suffer from that issue?

[EricJ]

3 minutes ago, Fly Boomer said:

What kind of meter doesn't suffer from that issue?

A faulty one.

The issue isn't the meter, it's how DC current works.    If you test the circuit with no load, you'll get the no load voltage.   Once a load is applied, then what happens isn't an issue with the meter, it's an issue with the circuit.    FWIW, you can test the voltage loaded or unloaded, i.e., test it again with the light connected and "on".   If there's insufficient voltage to drive the lamp, then there's a load or a supply issue.

[Guest]

So this silly little light is getting beyond me. I hooked the battery straight to the socket and it works.  So like N201MKturbo said I must not be getting enough amperage back to it. How does one go about finding where one is loosing the amperage?

[N201MKTurbo]

3 minutes ago, Kerrville said:

So this silly little light is getting beyond me. I hooked the battery straight to the socket and it works.  So like N201MKturbo said I must not be getting enough amperage back to it. How does one go about finding where one is loosing the amperage?

You just have to work your way from the light to the switch. I think your next connection is in the gap between tail and the fuselage. I believe there is a handshake splice in there for the tail light so you can remove the tail. Take that splice apart and apply 12V there and see if the light lights up.

[Guest]

Thanks. There is a connection for the ground wire in the rudder. It is ugly looking. (See picture.)The next connection that I see is a pair of butt splice connectors near the battery box. I will try to put the voltage there first since it is easier. Can I replace the butt splices with Home Depot ones, or is there an approved splice? 

[Rwsavory]

Don’t use Home Depot or similar stuff. Either go to Aircraft Spruce and shop around, or visit your friendly A&P or Avionics tech. It will take them about 5 minutes to make it right. 

[Utah20Gflyer]

7 minutes ago, Kerrville said:

Thanks. There is a connection for the ground wire in the rudder. It is ugly looking. (See picture.)The next connection that I see is a pair of butt splice connectors near the battery box. I will try to put the voltage there first since it is easier. Can I replace the butt splices with Home Depot ones, or is there an approved splice? 

The ground circuit is notorious for creating weird symptoms so it would be my primary area of concern at this point.
 

if it isn’t too much work you might consider running a new ground wire that doesn’t have a bunch of splices.  If you do splice it again use one that has the pre applied solder in it.  I wouldn’t trust a ground that is just a compression crimp.  Also make sure the connection is protected from corrosion by heat shrink tape.  
 

 

[PT20J]

47 minutes ago, Kerrville said:

Thanks. There is a connection for the ground wire in the rudder. It is ugly looking. (See picture.)The next connection that I see is a pair of butt splice connectors near the battery box. I will try to put the voltage there first since it is easier. Can I replace the butt splices with Home Depot ones, or is there an approved splice? 

The ground connection “splice” looks like a knife disconnect so that the socket can be removed. 

Auto store butt splices usually only crimp the bare part of the wire providing little strain relief. You want PIDG butt splices that have a second crimp for the insulated portion also. The best ones are heat shrinkable after crimping to form a seal around the insulation. Be sure to use the proper crimper.

https://www.te.com/usa-en/products/brands/pidg.html?tab=pgp-story

These are available from Aircraft Spruce and others.

[larryb]

In my Mooney there is a circular connector in the open space, behind the fairing, between the fuselage and the tail. This connector is not water proof but it is in an are where it gets wet. When my plane had it's LED strobe upgrade this connector still worked but was found to be corroded. It's another place to check. 

 

What you are looking for is a high resistance connection. For the ground you can test this easily by measuring the resistance between the body of the socket and the airframe. It should be well under 1 ohm. I doubt it's the ground because even if the wire is bad, the light should work if the socket is mounted to the tail. Mounting it would complete the ground connection. 

[EricJ]

For crimp connections the crimper is more critical than the butt joint used.   A high quality butt joint with insufficient crimp is not any better than a cheap butt joint.

Just use decent quality butt joints, imho they don't need to be anything crazy, and there really isn't such a thing as an "aviation" butt joint.    If the joint will be somewhere that moisture may be an issue, then use the kind with heat shrink ends and shrink it after it has been crimped, or put a sleeve of heat shrink over it when you make the splice.    Crimped joints are preferred over solder or solder seal joints because solder causes stress risers under flex or vibration that ultimately cause wire breaks.

Don't splice adjacent wires at the same spot, stagger the splices.   There is also a limit of one splice between connectors.   See AC 43-13  11-167.

Use a ratcheting crimper with the proper jaws, like the one linked below.   AC 43.13 says only a little bit about general suggestions regarding the type of splice connectors (11.167b), but has an entire section (11.178) on the requirements for the crimping tool.

https://www.amazon.com/gp/aw/d/B07Q32PYP3

[Guest]

I don’t think the rudder itself is grounded. If so, I haven’t seen the bonding strap. The ground wire runs from the solder outside the socket to the ugly splice, then to a butt connector near the battery box, then forward to parts unknown (I haven’t traced it yet.)

[N201MKTurbo]

34 minutes ago, Kerrville said:

I don’t think the rudder itself is grounded. If so, I haven’t seen the bonding strap. The ground wire runs from the solder outside the socket to the ugly splice, then to a butt connector near the battery box, then forward to parts unknown (I haven’t traced it yet.)

That is a properly done factory splice BTW.

[wombat]

2 hours ago, Rwsavory said:

Don’t use Home Depot or similar stuff. Either go to Aircraft Spruce and shop around, or visit your friendly A&P or Avionics tech. It will take them about 5 minutes to make it right. 

While I agree with you not to use Home Depot, I have yet to find anything at all that takes an A&P less than 30 minutes.

Example:  Switching my left position light from one that had frame ground to one that had a ground wire, grounding that wire on the aircraft structure about 2" away.  Just doing the ground took about an hour and a half.  Not even talking about mounting the new light or the paperwork for that.  JUST the ground wire.   And as a favor to me, he didn't bother to make a logbook entry for the ground wire.

Here are the steps he took:    Remove wingtip, disconnect position light power.  (8 phillips screws, 2 zip ties and a electrical connector)   took about 10 minutes.    Review install manual for position light, notice that it has a ground wire instead of being self-grounding on the frame.    Try to look up the ground wire size.   Find install manual for new position light & search for appropriate section then eventually determine that there is no specification in the install manual.     Next he found the maximum draw of the light, which was in the manual.     Then over to another document to determine the wire size based on maximum draw.    This part took about 20 minutes.  After that, he went to find a bolt, nut, washer, lock washer, wire, and ring terminal to use, ensuring that all are the correct size for this application.   This took perhaps 10 more minutes.   Cut the wire to length, strip, and crimp on the terminal connector.    Then over to the aircraft with supplies, and note that the structure doesn't have any holes appropriate for the grounding wire post.    Back to the books to get the drill bit size for the bolt, then over to the bench to get a drill bit and drill.   Back to the plane to drill a hole in the rib.     But the metal is old, so go back to the tool bench to get some scotch brite, and 5 minutes of work on that section to get rid of any surface corrosion and debur the hole.     Oh, but now there are shavings in the wing, so go get the vacuum.     Vacuum up the mess in the wing.      Then put the drill and vacuum and scotch brite away.   That was 10 more minutes.  Then back to the plane, assemble the post, washers, nut, lock washers, and ground wire.     Go back and get a screwdriver and ratchet with appropriate size driver for the nut.     Guess at torque values and tighten them down.  Another 15 minutes.   Now back to the bench and get some corrosion-X and spray down the area that we scuffed clean so it doesn't corrode since the raw aluminum is exposed again.     Total time was about 90 minutes and the end result is we've added a ground wire about 4" long.

[Rwsavory]

You should be thankful that your mechanic is so thorough. lol

[Guest]

I think I will start with a wire direct to the battery ground to the socket. If that works, great, just run a new wire…

[wombat]

15 minutes ago, Rwsavory said:

You should be thankful that your mechanic is so thorough. lol

I'm only barely complaining.   I want folks to understand that there is unlikely to be a 5 minute fix for anything.  Even a simple ground wire takes a bunch of time.

[EricJ]

49 minutes ago, Kerrville said:

I think I will start with a wire direct to the battery ground to the socket. If that works, great, just run a new wire…

One thing you can try if you can get a probe on it, is to see if there is any voltage between the ground on the light fixture and the airframe while the light is on (i.e., current is flowing).   That'll show if you there's a voltage drop, and therefore resistance, across the ground wire returning up the airframe.    You could try just checking from the fixture to the rudder, and/or to the airframe at the tail past the rudder.