Mystery wire

[rotorman]

I purchased the Whalen anti-collision beacon, OR36R recently. The installation is about a simple as it gets with one exception. I removed the 1980 original Whalen rotating beacon. There are two wires coming out of the the tail cone, both white. One is 12v. The other is a mystery. It does not test as a ground wire. It was screwed to the top of the beacon adapter unit with a ring connector. The old beacon and motor were grounded by contact to the tail cone and mounting so no ground wire was needed. The OR36R can be grounded the same way.

Any idea what this wire was used for?  I don't want to leave this mystery wire without a home.

 

 

[PT20J]

Most likely it is a ground. Mooneys (at least M20Js and later) don’t depend on the airframe for a ground return but run ground wires back to grounding connectors behind the instrument panel for all circuits. You’d have to trace it out to find out where it has become disconnected. 

[carusoam]

Let’s see…

1) A Whelen question…

2) A good Whelen question…

3) If we had a good Whelen guy around here….

 

Wait a sec….  @OSUAV8TER (technical wiring question for a Whelen anti-collision beacon questions….)

I’m pretty sure we have a good Whelen guy around here… 

 

Best regards,

-a-

[OSUAV8TER]

It could be a ground or it could be a sync wire if it is connected with wingtip or tail strobe lights (some old models could do that). The Orion 360 LED beacon cannot do that so if that was its old purpose, you can remove it or cap and stow it.

[rotorman]

13 hours ago, PT20J said:

Most likely it is a ground. Mooneys (at least M20Js and later) don’t depend on the airframe for a ground return but run ground wires back to grounding connectors behind the instrument panel for all circuits. You’d have to trace it out to find out where it has become disconnected. 

Either by coincidence or by cause, the next time I ran the engine after the new beacon was installed, the ammeter was swinging from stop to stop coupled with a whine in the headset. I had seen this before a few years back and tried cleaning the master switch connectors to no avail. It did finally quit but I can't recall under what circumstances.

What is the technique for tracing a wire that disappears into a bundle?

[EricJ]

1 hour ago, rotorman said:

Either by coincidence or by cause, the next time I ran the engine after the new beacon was installed, the ammeter was swinging from stop to stop coupled with a whine in the headset. I had seen this before a few years back and tried cleaning the master switch connectors to no avail. It did finally quit but I can't recall under what circumstances.

What is the technique for tracing a wire that disappears into a bundle?

A wire tracer, sometimes called a "fox and hound" will work *sometimes*.    They're decent if you have an idea of which connector is on the far end and just need to know which pin a wire goes to, and once in a while you can trace the whole wire path with it.   If the wire disappears into a bundle or is shielded the effectiveness may not be as good.    Often worth a shot, though.

Here are a couple examples, but there are quite a few different kinds.

Edit:  These things are very good at selecting the correct "other end" of a wire from possible candidates.   In other words, if you hook up the tone generator to the known end and have a few candidate "other ends", these are good for isolating the correct "other end".

https://www.amazon.com/Sperry-Instruments-ET64220-Installers-Must-Have/dp/B00279JLBQ

https://www.amazon.com/Fluke-Networks-26000900-Pro3000-Generator/dp/B000FTADX0

 

 

Edited April 4, 2022 by EricJ

[Aerodon]

I have one of these cable testers with a total of 4 expansion slots, 12 different boards and more than 20 cables that can plug into just about every aviation connector in the plane. Even the Garmin 78 pin HD connectors, Winchester connectors (Bendix King) etc.   If it is a loose wire, one of the tester cables has 10 mini clips.   It tests every pin against every other pin and can generate a useable wiring diagram and a pin to pin list in seconds.

This is a really excellent way of generating 'as-built' wiring diagrams testing against a known configuration for pass/fail and also trouble shooting existing installations.

Aerodon

 

 

[rotorman]

Based on these suggestions for different types of wire tracing devices I can see that you guys are way out of my league. I can run a multimeter and that's about it. 

My initial thought on this old rotating beacon installation was that the mystery wire had to be a ground as PT20J has suggested.  And since it no longer has continuity to the airframe, along the way it was cut or disconnected, but the beacon still worked because of beacon case to airframe contact. I should probably wire in a new ground and connect it to the new anti-collision light beacon.

[A64Pilot]

The older an aircraft gets, the more wires to nowhere there are. ADF, LORAN, DME, replaced NavComms, all left wires behind.

 I was under mine the other day wondering why I had two Xponder antenna’s, the Transponder wasn’t diversity? Then it hit me, I bet this thing at one time had a DME.

And guess what, both still have Co-ax connected to each one, so which is the Xponder?

A FAA friend told me the average aircraft had four or five comm radios, seems 337’s are filled out for installation, but none for removal

Edited April 6, 2022 by A64Pilot