Scudrunners

So pre-flightimg the Stinson, I notice my position lights don't work.
Well, shit. I guess I won't fly at night.
Barely a few minutes I flip the switch again, just because, and they work! (They're tied into to panel lights)

So I try this again a few more times over a few more flights, and this seems to be the case.
What the hell is going on, where it takes a few minutes of flight (vibrations of a loose wire?)

Has anyone chased a ghost like this?

If it's one light that's not working check that light.  If it's all the lights check the switch / back to the buss.

Basically cut the system in half.  You can eliminate most of the wiring going to the lights because they either all work or don't.  So the problem has to exist either where they all congregate (the switch) or where the switch is getting it's power.  So check the switch, and if it is working then there's really only one remaining possible cause

I will speculate because I don't know enough without looking at the actual  systems.

I suspect you have an electrical starter.

Being a nice small plane we want to keep weight down. Your battery will be a plastic box full of lead plates and liquid acid. You want one as small as possible while still being able to crank a bit to start the engine. You also want as small as possible generator or alternator ( depending partially on age of the system ) to recharge the battery.

So, just after start up the battery will be fairly low on stored energy and need to be recharged. It will draw quite a bit more of the power from the charging system initially then it will a couple minutes later, the battery will still be drawing power for a while after that to recharge, but significantly less than the first few minutes.

The lights might be coming on but much dimmer just after start up time. You may have never noticed at night as they came on dimmer then got brighter. During bright daylight the lights might be so dim they cannot be seen as on until the battery settles.

As the battery ages it can exaggerate the process since the lead plates are slowly getting contaminated and hold less electrons and therefore less charge. The charging system might have an issue preventing the full amount of charge it used to provide also.

I would ask around to see if there is an AME near you with really good electrical knowledge. Preferably one with knowledge/experience on type, being a nice older plane it is likely equipped with a mechanical regulator. There might be a really great direct plug electronic replacement regulator but being an airplane it could be really over priced.

Are you a member of a Stinson club. I hope it is just normal and you never turned the lights on early enough to notice.

If the battery has enough current available to push a starter 4 amps worth of lights will come on when the switch is flicked.

This is a simple problem.. batteries and alternators aren't it.  If those were a problem you would be here describing different symptoms.  It'd be willing to bet money it is the switch (wiggle the switch and feel for slop) a corroded terminal block or both.  Don't waste money barking up the wrong tree troubleshooting your regulator/generator or alternator.

Thanks for the reply.

I'm not sure it's in the alternator output/battery storage. I just replaced the battery in Jan.
(Different issue at the time, but the alt puts out lots of juice)

I think the issue is in the switch. (All position + panel lights will come on after X amount of minutes.)

I am a member of the online group, but didn't think to ask there.

As donutHole says, try the simple free things before spending any money. And like you say a loose connection can do strange things. A corroded or dirty or oily connection might not conduct enough amperage ( possibly none ) until it warms up.

It certainly could be the switch but because it is taking a few minutes, then they turn on, is throwing me off. if the switch was loose or intermittent it should not show that pattern.

This is a problem with trouble shooting via text or worse yet over the phone. I was thinking about how the lights are not working at first after start up, but then work after things get "warmed up."

I wonder if you start it, then shut off the alternator. Do the lights come on? Do they come on after a minute or few minutes?

Sometimes it is difficult to isolate an electrical problem as a component might seem to be fine when it is by its self, then not work right as part of a system.

The reason I suggested an AME with experience on type is if you get lucky and find the right guy he or she might take a look a say, "Oh that is the ( item that they have seen do what it is doing ) simple to fix, just...."

Sometimes even the best guy will be wrong too but they will be more likely to figure it out quick than me.

Mr MacKay,

It's funny, I had a idling issue when I first purchased it. I mentioned it to a fellow Stinson guy. He said exactly what you are saying, "check this, this and this."  Sure enough, it was the intake manifold connection right by the front/prop. Narrowed it down in seconds.

I'll be out on the town, but I'll report back as soon as I can.

Thanks again. Have a great night.

Patterns are useful for troubleshooting but they also offer up their fair share of red herrings.

In thinking about this problem I pretty much rejected the pattern as part of the process.  It's a red herring.  The real symptoms are sometimes the lights work, and sometimes they don't.  Having a pretty good deal of electrical troubleshooting experience my draw from that experience tells me that chasing down the time constant of this problem is a useless endeavor and can probably be rejected in determining causation.

There are so few components in a simple lighting system.  We aren't talking about capacitive discharge or anything more complex, it's a switch turning on a few lights. In that system there is a switch, connectors, wires, and lights.  The batch nature (either all or nothing) points directly to whatever is common in those systems, which is the switch, the buss and the connectors between the buss and the switch, and the connectors on the switched output of the switch.  Logically speaking those are the places where you will find your problem.

Troubleshooting the switch: wiggle the switch post with the switch in the on position.  Turn it on and wiggle it back and forth up and down while it is still in the latched on position.  If your lights come on its probably the internal switch poles or the actual swing mechanism in the switch.

Troubleshooting the wires: I rarely see wires go bad.  Like almost never.  It's almost always the mechanical pieces or the mechanical connections (the ring terminal crimps) which can fail in a few ways

Troubleshooting the connections: the connections can fail in a few ways.  The most common is corrosion.  If you are near the salt corrosion will be a problem. To troubleshoot corrosion you basically need to do a visual inspection.  Any white powder or green crust is a giveaway. 

The second most common is work hardening of the wire/connector interface.  This is a tricky one.  To troubleshoot it you need to wiggle the wire at the connection.  Tug on it (if it was crimped properly you shouldn't be able to tug it out) most of the time the wire will either be broken, or corroded so badly it breaks at the joint.

If you tug on it and the wire comes out off the terminal you have an installation problem and now a corrosion problem.

How to fix it ranges.  You can carefully clean the wires and if you have enough of a service loop you can put a new connector on and bobs your uncle, if it's really bad and the corrosion has crept down the wire then you might have to replace the wire.

I said before the wire isn't usually the problem and now here I am telling you you might need to replace the wire.  Even if a wire is corroded into the insulation (you can tell when you strip it, it will be black) if there isn't a problem in the connection itself your system will probably work.

Anyways there you go.  That's what I would start with.  With your symptoms I would check at the fuse holder or breaker and work my way towards the switch.  It'll be obvious when you find it.

Good luck and of course make sure you have an Ame  or ia do this work if you aren't paper qualified yourself.

[quote]I rarely see wires go bad[/quote]

GA aircraft are getting old enough that
deterioration of the wiring insulation is
getting to be a possibility.

Bobby had a "dead mag" on one of this
aircraft a few years back.  First thing I
did of course was to disconnect the p-lead
(mag hot for testing) and it worked!

Problem turned out to be a bad wire,
grounding somewhere between the switch
and the mag.  Ran a new wire from the
switch to the mag, and it's still working fine.

If it's not an antique, 99% of the time the
problem is a connector or switch or contact
or something like that, at the end of a wire.

Here's a fun electrical problem:

[img][/img]

That's the logic analyzer trace for a Zilog USART
"after" I found and fixed the solder bridge
during SMT rework (not by me).

That incredibly cheap USB logic analyzer has
saved my bacon so many times ... here's
another trace:

[img][/img]

Notice the ringing?  My software was capturing
falling edges, and the fingers were pointed at
the software.

Not so fast.  Hardware isn't supposed to ring
like that!

https://en.wikipedia.org/wiki/Ringing_( ... lectricity

[quote author=DonutHole link=topic=370.msg1365#msg1365 date=1435469432]
Patterns are useful for troubleshooting but they also offer up their fair share of red herrings.

Troubleshooting the wires: I rarely see wires go bad.  Like almost never.  It's almost always the mechanical pieces or the mechanical connections (the ring terminal crimps) which can fail in a few ways

[/quote]

Good post DH.  I'll add one data point on this subject.  If a wire is subject to flexing in normal use, it then becomes a suspect as well.  I once found a broken wire in cruise control wiring in the tilt steering wheel mechanism of a truck I used to own.  I found a soft spot that flexed easier than the rest of the wire, cut it there and spliced it.  Worked fine from then on, and left the wheel in one position after that.

Not likely an issue in a Stinson, but always worth keeping in mind when chasing electrical gremlins.

Gerry