NAV Lights troubleshooting... any thoughts ?

Piper_Six

Piper_Six

Pre-Flight
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1959 Bonqnza K35
So... just found on pre-flight... NAV lights/position lights not working. Beacon works, both side landing lights work, but not NAV (Separate switch, from beacon and Landing Lights).

Since all three lights aren't working, (left, right and rear position), it is possibly not just a bulb issue?

Here is an interesting thing... This is a 1959 Bonanza K-35, and it has that single light for gear and flap, which are fairly dim, but get very bright if the NAV switch is OFF. Even though the NAV lights aren't working, these annunciator lights still do dim and go bright when I cycle the NAV switch from on to off. But if the three lights aren't coming ON, it shouldn't technically draw any current and hence, not make a difference to the brightness of these lights?

Can ALL 3 bulbs be burnt at the same time?
Any thoughts on where to begin troubleshooting ?
 
Piper_Six said:
So... just found on pre-flight... NAV lights/position lights not working. Beacon works, both side landing lights work, but not NAV (Separate switch, from beacon and Landing Lights).

Since all three lights aren't working, (left, right and rear position), it is possibly not just a bulb issue?

Here is an interesting thing... This is a 1959 Bonanza K-35, and it has that single light for gear and flap, which are fairly dim, but get very bright if the NAV switch is OFF. Even though the NAV lights aren't working, these annunciator lights still do dim and go bright when I cycle the NAV switch from on to off. But if the three lights aren't coming ON, it shouldn't technically draw any current and hence, not make a difference to the brightness of these lights?

Can ALL 3 bulbs be burnt at the same time?
Any thoughts on where to begin troubleshooting ?
Click to expand...
Could be the power supply. Mine is in the tail. I'll post you a picture of it.

Edit: sorry you said Nav lights and I went with strobe. I'm a little slow sometimes...
 
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Hmm... well, the strobes aren't coming on either... meaning, the ones on the wing tips, the beacon on top of the fuselage, flashes on with the beacon switch.

Thanks for posting... I'll check that out.
 
Piper_Six said:
Hmm... well, the strobes aren't coming on either... meaning, the ones on the wing tips, the beacon on top of the fuselage, flashes on with the beacon switch.

Thanks for posting... I'll check that out.
Click to expand...
I believe my beacon is not connected to this box. Scary thing is a new one is like $900. Yay airplanes.
 
Piper_Six said:
...these annunciator lights still do dim and go bright when I cycle the NAV switch from on to off...
Click to expand...

Just a guess but that's probably just a circuit dimmer function - nav lights on, it's night so dim the interior indicator lights. Doesn't have anything to do with current draw of the bulbs. As for all three bulbs going bad, probably not if it's something that gets checked frequently. We had a problem on a 787 where all of the lights in the electronics bay were out. Techs had the wiring diagrams out and were deep into troubleshooting convinced it was impossible that all eight bulbs were burnt out. I made the suggestion to just take one new bulb up there and see if it works. Turns out that nobody will make a write up until the last one goes out.
 
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Initial guess would be an issue with the switch (this is the old piano-key switch, right?), but since your gear lights dim as they're supposed to, at least part of the switch works properly. You might take your query over to Beechtalk for more specific info.
 
Step 1, check the fuse. Wouldn't hurt to check for power at one of the lights just to rule out burned out bulbs.

Step 2, obtain a wiring diagram.
Someone suggested that there may be a dimming function associated with the nav lights. The diagram should show it. And knowing this changes the diagnostics quite a bit.

Step 3, divide and conquer. Check for power somewhere in the circuit - perhaps the switch. That tells you which direction you need to go to find the fault.
 
Some Pipers have a resistor to dim Indicator lights when Nav Lights are ON.

This avoids being tooo bright at night.

I agree with preceding .

Important to know that all 3 Nav Lights first go through a fuse/breaker and then

a. Switch before dividing up 3 ways.

Hence if any of the 3 lights has a wire that has shorted to ground

the fuse / breaker will open the circuit.
 
Checking voltage is a good suggestion. On my Warrior, I have had to repair ground straps on the wing tips several times so check ground as well.
 
Since all three are out at the same time, one would normally expect that there's a common denominator at work here. Normally, all three wires terminate at the switch, so the first thing a mechanic would do is crawl under the panel and take a good look at that switch and the wires connected to it. Since there's a panel light dimming function, that switch might be an SPDT or DPDT type, with the Nav light side of it shot. A voltmeter and the skills to use it are a prime way to save time and money and frustration.

I don't have a manual for that airplane and couldn't find a free pdf of one online. If someone has a manual applicable to that airplane, maybe they could post a shot of the nav light circuit wiring diagram. Such information is priceless.
 
Bell206 said:
https://aircraftassociates.com/_files/200003154-b7c72b7c74/Bonanza 35 Shop Manual-compressed.pdf
Click to expand...
There we are. Thanks for that. Here's the circuit for the Nav lights in the OP's airplane:

upload_2021-1-5_17-32-31.png

The Nav light switch is a 3PST, with one section operating the nav lights and the other two shorting the dimming resistors for the gear and flap lights when the nav lights are off. Shorting the resistors make the indicator lights bright.

A quick check of voltage at the Nav light terminal on that switch, the one with three wires attached to it, and the with switch on (and master on) should show if the switch is pooched. Check the voltage at the breaker connection to that section of the switch as well, again with the master and nav lights on. Old breakers cause all sorts of hassles. A switch or breaker with an internal resistance can show as good on a voltmeter when there's no load connected.

Of course, maybe the screw holding those three terminals fell out and the wires are disconnected. If so, there's the likely problem. Reconnecting them should light things up, and if it doesn't, check the voltage again and see if it's OK.
 
Thank you for the schematic... was able to get to the hangar today, and checked, all 3 bulbs are functional - took them out and gave it 12V from a spare battery and lit up good. So that rules out bulbs. Next, with the master & NAV light switch in ON position, measured voltage at the terminals where bulbs were just removed... nothing... no juice... checked all three positions. Now to trace wiring from bus to switch and on ... ugh that will be interesting.... one peek under the piano switch panel...this is going to be a project....

One question... from the schematic... is there an in-line fuse from the bus to the switch ? I don't have any circuit breakers for NAV light on the panels anywhere... the shop manual does say (pg. 3-45) to check breaker...right now.. accessing the back end of the piano switch is posing to be quite a challenge.
 

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Been a while since I was under one. Yes its a pain. More often than not, its a ground that is "open". But that said, start at the power source. Make sure you have 12 volts to the switch, and that you have power coming out of the switch, and so on, running down the wires. Yes a PAI. There "must" be a fuse/breaker for all circuits. Doesn't mean there is.
 
Piper_Six said:
One question... from the schematic... is there an in-line fuse from the bus to the switch ? I don't have any circuit breakers for NAV light on the panels anywhere... the shop manual does say (pg. 3-45) to check breaker...right now.. accessing the back end of the piano switch is posing to be quite a challenge.
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The schematic shows a breaker for the Nav lights. Are there any breakers located somewhere other than in plain sight on the panel? Or maybe a breaker is mislabelled.

Lots of fun getting under the panel of a low-winger. The spar carrythrough makes it miserable. One can't get comfortable enough to concentrate on getting a good look. A mirror and flashlight are handy, and sometimes a snake camera will let you look at stuff from a more comfortable location. Fixing it will still be tough, though.

Give me a Cessna single anytime for this sort of thing. Except the 150; it has a big ridge in the floor right under the front of the seats.
 
Some of the auto guys have a device where you can but power IN

at each light.

Don’t know what it’s called but good for diagnosis.
 
Ahh yes, #5 on the schematic - I thought that was a notation for the bus to switch wire. So the other designations, such as L10-18 etc are supposed to be labels on the wires ? Ugh... Yes, I remember during the Alternator/Voltage regulator episode, the Hartzelle rep had to basically put is head on the rudder pedals, feet over the seat back, almost looked like an astronaut buckled in for launch ;) ... that explains why he asked if I had a pillow around... ;)
 

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Piper_Six said:
Ahh yes, #5 on the schematic - I thought that was a notation for the bus to switch wire. So the other designations, such as L10-18 etc are supposed to be labels on the wires ? Ugh... Yes, I remember during the Alternator/Voltage regulator episode, the Hartzelle rep had to basically put is head on the rudder pedals, feet over the seat back, almost looked like an astronaut buckled in for launch ;) ... that explains why he asked if I had a pillow around... ;)
Click to expand...
Seats need to come out of the airplane.
They make the job way worse and they can get scuffed up.
 
NAV Lights finally fixed, had the seats out during annual, so that helped. It helps to throw a pillow on the rudder pedals so you can rest your head on it, and the head-lamp allows both hands to fiddle with the wires... all good now.
 
Piper_Six said:
NAV Lights finally fixed, had the seats out during annual, so that helped. It helps to throw a pillow on the rudder pedals so you can rest your head on it, and the head-lamp allows both hands to fiddle with the wires... all good now.
Click to expand...
So what did you find? Broken wire?
 
jsstevens said:
So what did you find? Broken wire?
Click to expand...

Ahhhhhh I was hoping no one would ask .... ;) I am extremely embarrassed to admit... For some odd reason my A&P said he didn't see a breaker for NAV lights, but after spending agonizing amounts of time under the dash laying on the rudder pedals... and finding no loose wires, a new assistant that the A&P had recently hired, saw this faded red breaker with a label below that said "NAV Lights" and .... once that was pushed in... the wing tip lights came on... the tail was out, but again, it wasn't the bulb, the ground wire (shielded) had snapped off the light bulb fixture, and after we soldered that back on, all lights worked fine. I think the breaker had popped when this wire snapped off ?

Having removed the light covers and all, went ahead and replaced them with LED bulbs. BIG lesson learned :) [adding it to the (short) list of dumb things I've done]

Before the beatings begin.. please give me some credit for sharing ;)
 
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You won't ever make THAT mistake again.
 
Always start at the voltage source (circuit breaker or fuse) for complicated electrical problems.
Afterseeimg the final response that it is cured, what is the chance of relocating that hidden breaker to a more accessible and safer place?
 
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Probably not your problem but we had an intermittant problem with our nav lights in the Navion. We replaced the wire going out to the white light (it was easy to get to and every place that it passed through a string the rubber grommet had deteriorated over 50 years and flaked away). Didn't help. We were about to do the same with the wingtip lights (more involved) when we found that there was FOUR wires (one to the tail, one to the right wing, and two to the left wing). Pulling gently on the pair going to the left wing resulted in being able to tease out one disconnected 2 foot length. This had my mechanic a the time perplexed, but I knew what it was.

The Navion came from the factory with only two flap positions (full up and full down). However if you filed a notch in the panel you could stop it in between. As there was no flap indicator other than the handle or looking out the window, the instructions for filing that notch came with the requirement to put a light on the wing root so you could see the flap position at night.
At some point our light got removed but the wire was left there with a piece of tape on it. After many years the tape fell off and the thing would intermittently hit the airframe.
 
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