M20R nav light won't turn off??

[flyingcheesehead]

Hi all,

I'm having an odd electrical issue and I'm hoping someone has an M20R wiring diagram or can offer some insight on how this might be happening.

I have LED nav lights installed a year ago from Aero-Lites - It's a model they don't sell any more. The left one does not turn off when the nav light switch is turned off in the plane.

I started pulling breakers to see what other circuits could be causing this. It appears that the only breaker required to power them normally is the 40A Right Aux one - Is the switch also a breaker?

Now the really odd part. The juice that keeps it running can come from two different sources. If the Gear Warn breaker is in, the nav light will remain on at a medium (not full) intensity. If the Starter Relay breaker is in, it will remain on at a low intensity. Putting both in does result in a slightly higher intensity than just the Gear Warn breaker being in.

What could be causing this?

Thanks!

[chriscalandro]

Look at the drawing, do these all feed into a central control box on this airplane?

Sounds like something is leaking a small amount of voltage into the lighting line.  My guess is these circuits all are fed from some central module.

 

I'm in the vintage Mooney world so I'm not up to speed on how the R is wired.

[carusoam]

Start with the POH... where should the Nav lights be CB’d? (Right side panel of CBs marked Nav lights?) I looked in the POH 7-25... exterior lights... no joy.

The oddity is the Nav lights in my O all come on with one switch... really two... Master and nav lights...

But... the nav lights are also connected to things like the dimmer function...

When the The nav lights are turned on, the annunciator panel will only come on half bright...

Isn’t the avionics CB switch live when the switch is off, and the master is off?

Try something funky... Master off, avionics on... does that change the light status?

 

So...

You have one nav light that comes on half bright... while the master is off...  time to call the doc... @M20Doc...

PP thoughts only, not a mechanic....

Best regards,

-a-

[flyingcheesehead]

10 hours ago, chriscalandro said:

Look at the drawing, do these all feed into a central control box on this airplane?

That's just the problem - I don't have the drawing! For my s/n it should be number 800304 R5 Rev Y, but a schematic for any R should be better than the only one I could find which was for a J and thus missing recognition lights and other stuff that's running out there.

[Cruiser]

I assume that the light did work properly at some time.

Was any other work done since the lights were installed ?

Do you have a drawing of the Aero-Lites installation ? Or the installation instructions ? I can't believe there is no breaker or fuse in the power line. 

How do you turn off the left nav light now?

 

 

[larryb]

Is this a new behavior, or something that you just recently noticed?

I think Carusoam is on to something mentioning the annunciator panel. That panel is powered by a number of circuits, like the ones you mention above. Depending on exactly how Mooney designed the electronics in the annunciator panel, it is possible that there is current leaking back from the circuit they use to monitor the Nav light circuit back into the nav lights and actually powering them. Remember that annunciator panel was designed before low power LED's. Just high power incandescent bulbs that would not be affected by a tiny bit of current back-flowing. With your original bulbs, the current would be there but there would be no visible effect. 

Another point, because the current involved is at the very bottom of what will light the lamps, it may be intermittent. It may work differently with different nav bulbs. And it may be temperature dependent. 

I suspect there may be nothing wrong at all. You could live with it as-is. Or you could fix it with a diode in the wire from the nav lights to the Annunciator panel. It could also be fixed with a relay in the nav light circuit. 

As a next step I would measure the voltage at both left and right nav lights in all 3 conditions: full  on, starter CB on, and gear warn CB on. 

[chriscalandro]

I looked through the maintenance manual and I agree with the above, it’s getting a small amount of voltage leakage through somewhere, probably the panel. 
 

it’s probably done it since the LEDs were installed. I wouldn’t worry about it. Like stated above, it takes a small amount of power to light an LED vs a incandescent. The wiring harnesses and circuit boards were not designed with this in mind, and a bit of leakage between circuits is probably normal behavior. 
 

id leave it alone and continue on my way. 

[ArtVandelay]

I had this with my J, there is a wire that autodims the gear down light when navigation lights are on, therefore the voltage is coming from the gear down circuitry. I fixed it when I removed my annunciator, and cap off the wire.

[StevenL757]

Exactly right.  It's not an abnormal condition...simply a by-product of moving some lights in your airplane to LED.  I believe there's a resistor (?) that can be added behind the annunciator panel to alleviate the condition.  Personally, I chose not to implement it, as it really is a non-issue for me.  Others' mileage may vary...

[flyingcheesehead]

14 hours ago, Cruiser said:

I assume that the light did work properly at some time.

Was any other work done since the lights were installed ?

Do you have a drawing of the Aero-Lites installation ? Or the installation instructions ? I can't believe there is no breaker or fuse in the power line. 

How do you turn off the left nav light now?

Well... Uh... I'm not sure it did. This is the first year in 17 years of flying that I've ever been not night current. Haven't used the lights a ton, and the only time I'd have them off with the master on would be during the day. It was the shop that discovered it at annual, and I told them to stop troubleshooting it because most shops aren't particularly good at electrical stuff.

No other work done since lights were installed.

I can't find the installation instructions, but they were pretty primitive. I mean, it's a simple bulb replacement. It was a single sheet. There's nothing new about the wiring. It sounds like the switch itself is also a breaker for the lights (as it was from the factory).

How do I turn it off now? Well, with the master.

12 hours ago, larryb said:

Is this a new behavior, or something that you just recently noticed?

I think Carusoam is on to something mentioning the annunciator panel. That panel is powered by a number of circuits, like the ones you mention above. Depending on exactly how Mooney designed the electronics in the annunciator panel, it is possible that there is current leaking back from the circuit they use to monitor the Nav light circuit back into the nav lights and actually powering them. Remember that annunciator panel was designed before low power LED's. Just high power incandescent bulbs that would not be affected by a tiny bit of current back-flowing. With your original bulbs, the current would be there but there would be no visible effect. 

Another point, because the current involved is at the very bottom of what will light the lamps, it may be intermittent. It may work differently with different nav bulbs. And it may be temperature dependent. 

I suspect there may be nothing wrong at all. You could live with it as-is. Or you could fix it with a diode in the wire from the nav lights to the Annunciator panel. It could also be fixed with a relay in the nav light circuit. 

As a next step I would measure the voltage at both left and right nav lights in all 3 conditions: full  on, starter CB on, and gear warn CB on. 

Yes, that'll probably be the next thing I do... But I'm also pretty certain that it is coming from the annunciator panel. Got some PMs to that effect as well. That's the only place I can figure out where it'd be leaking current from the starter relay CB. ("START POWER" is one of the annunciators.)

[PT20J]

The Mooney Parts Manager Steve Rue was pretty helpful supplying pdf service manuals, schematics and IPCs. Now that the factory is shut, I would still think you could get them through a MSC. Really should have them if working on you own airplane. Also very handy when you are on the road with a problem and the local mechanic doesn’t have the docs for your model.   
Skip