Whelen strobe troubleshooting

[Jim_R]

At annual 18 mos ago, I added Whelen wingtip strobes to my PA28, including ballast. I already had a beacon strobe on the tail. Not exactly sure how it all got wired, but the new tip strobes were tied to the same switch as the beacon.

Over the last several months, I've noticed that the strobes don't always come on when I flip the panel switch. First time it happened, the plane had been sitting for a while and I turned on the strobes prior to cranking the engine, so I suspected maybe the battery was weak. I turned off the strobe switch and started the engine, then switched the strobes on and they worked.

This same sequence of events happened occasionally over the next several weeks. Then, one day, the strobes wouldn't come on even after the engine started. Cycling the switch once would generally get them going, but sometimes it took two cycles.

Now, the problem has gotten so bad that multiple switch cycles still won't get them to fire up. However, I seem to have good luck if I leave the switch on for several minutes (like during taxi/run-up), and then do a quick off/on cycle. So far, that's gotten the strobes started every time.

I am guessing this is a gradual failure of the ballast...at least, I've seen ballasts in fluorescent light fixtures degrade over time with almost exactly the same behavior, so that seems reasonable.

This is pretty disappointing, since the system was purchased and installed less than two years ago. Is this typical? What sort of lifespan should I reasonably expect from a Whelen ballast?

I haven't talked to my mechanic about it yet, but when I do, what should I expect to see him do to troubleshoot and diagnose the problem? (I think I've seen that Whelen sells dedicated diagnosis equipment for ballasts, but I don't think my mechanic has such a gizmo. Should I take it to someone who does?)

 

[Let'sgoflying!]

Next time the switch does not turn on the strobes I would like to know if there is current going to the power supply(ies).

(I'm sure you realize the jolt these things can give you if you touch the wrong connector, even with the power off)

I had to reballast my Whelan unit...maybe 8 years ago - they should easily last 10 years imo

 

[denverpilot]

Shouldn't be dead that soon, but I'd want to know how your battery and charging system are doing before getting too worried about the strobes.

Our strobes take quite a while to charge up and fire when on battery power alone. Engine running they're virtually instant.

If the battery or alternator are weak the strobes are probably one of the first places you'd see it.

Now you have me curious. I need to go log diving to see if any work has ever been done on our strobes. There's a good chance they're the originals from 1975. But I'll look.

 

[Hiperbiper]

Jim;
A few questions please.
Do you have a single strobe power supply (413 series) that powers both lights or did you get the 490 series that are installed at each wingtip light?

When your wing strobes fail to come on does your tail beacon come on?

Speaking of the tail beacon; is it a stock Piper flasher type or a real Strobe type system?

Last but not least, is the switch for the tail beacon a stock looking switch or an obivously aftermarket install?

Chris

 

[gismo]

There could be several reasons why your strobes don't work. One would be a problem in the supply itself which could be temperature sensitive. Another common issue is that when the lamps get old they become harder to flash. Other potential issues are water/moisture in the lamp housing and improperly connected shields on the wires from the supply to the lamps (shields must be connected to airframe ground at the supply end only).

 

[SCCutler]

Answer Chris Carlson's questions above, and we can zero in pretty well on the problem. He asked all the questions i wanted to ask.

 

[Jim_R]

Jim;
A few questions please.
Do you have a single strobe power supply (413 series) that powers both lights or did you get the 490 series that are installed at each wingtip light?

It's the single remote unit; it's mounted just behind the battery box behind my cabin aft bulkhead. I remember it had an output for a tail strobe; I don't remember if the tail was connected to it or not--I'll check next time I'm at the hangar. (I suspect the original tail wiring was left in-place, as that would have been easier and there was no requirement to change it.)

When your wing strobes fail to come on does your tail beacon come on?

Good question--no, it does not. (And if its ballast is wired separately, that would tend to exonerate the ballasts and implicate the alternator/charging system.)

Speaking of the tail beacon; is it a stock Piper flasher type or a real Strobe type system?

If by "flasher" you mean rotating beacon, it is not. If there's another type of flasher besides rotating beacon and strobes, I'm not familiar with it, so I've always assumed it was a typical strobe. Visually, it looks like a Whelen p/n 9052055. I'll try to look through the maintenance logs and see if I can confirm that.

Last but not least, is the switch for the tail beacon a stock looking switch or an obivously aftermarket install?

Both the tail beacon and the wingtip strobes are tied to the same switch--the original factory rocker labeled "ANTI COLL LIGHTS" (which only turn on the strobes; position lights come on when one of the rheostats (either instr panel lights or cabin overhead light--I forget which) is clicked out of the "off" position).

To address a couple of other questions/comments:

• I have occasionally noticed fog/haze inside the strobe lamp housing during pre-flight checks. Should I pull the lamps at next annual and check/replace/reseat the grommets or perform some other maintenance to remove that moisture? (I always figured after the first couple of flashes, it'd be gone, so not a big deal.)
• I don't have a voltmeter, but engine usually turns right over, and ammeter needle shows what seems to be reasonable movement after engine start (short duration of "high" current draw that ramps down within 15-30 seconds to normal steady-state level based on loads). Have had no other obvious reason to suspect battery or alternator issues except for strobe performance.

Thanks to all for the help!

 

[brien23]

If you have a strobe system should the flash tube get black change it as it seems that the blacker they get the more they load the power supply system down and then it fails. Changing the bulb when they show black is cheaper than burning out the power supply.

 

[PilotAlan]

When your wing strobes fail to come on does your tail beacon come on?

Good question--no, it does not. (And if its ballast is wired separately, that would tend to exonerate the ballasts and implicate the alternator/charging system.)

If I understand correctly, the beacon strobe is separate from the tip strobes, but both activated from one switch. And both not working.

That points me to the switch itself, loss of power to the switch, wiring failure between the switch and the strobe power supplies, or the power supplies having a common bad ground.

But I'm not an electrician, so that is worth what you paid for it.

 

[denverpilot]

Your nav lights are on the same circuit as the interior lighting? Very odd.

 

[Hiperbiper]

Jim said:
Both the tail beacon and the wingtip strobes are tied to the same switch--the original factory rocker labeled "ANTI COLL LIGHTS" (which only turn on the strobes; position lights come on when one of the rheostats (either instr panel lights or cabin overhead light--I forget which) is clicked out of the "off" position).

JMPO: Pilot Alan is spot on.
From your discription; if both the tail (beacon) light and the light switch that turns it on are both stock (say a 6-7 amp load circuit) and someone ADDED the Whelen 413CF strobe power supply (8-10 amp load) to it (hopefully thru a seperate CB or fuse) I'd venture a guess the switch contacts are scorched...too much load and not enough switch!

The nav light/panel light thing is normal, it's a Piper thing...

Don't worry about your charging system. If everything else is working OK then this is an end device problem...

As to them working when you repeatedly operated the switch:
When you turned on your strobes with your bad switch you had 12.5 VDC without the engine running and they couldn't get enough juice thru the crappy degrading contatcs to load the power supply. After you started the engine you had 14.5 volts (and a bit of vibration) to overcome the poor contacts and stuff started to blink. As the switch got worse the resistance (heat) went up, the cooking contacts got worse and soon your lights stopped working all together...

If I'm right when you look under the panel you'll find the wires leading to the offending switch "browned" or discolored. Tefzel is hard to melt but it will color up if it gets hot...


Hope this helps;

Chris

 

[Jim_R]

As the switch got worse the resistance (heat) went up, the cooking contacts got worse and soon your lights stopped working all together...

Actually hasn't stopped working altogether quite yet, and once the strobes come on they stay on for the entire flight, but you've certainly given me something else to check!

 

[Dan Thomas]

As the switch got worse the resistance (heat) went up, the cooking contacts got worse and soon your lights stopped working all together...

If I'm right when you look under the panel you'll find the wires leading to the offending switch "browned" or discolored. Tefzel is hard to melt but it will color up if it gets hot...

An old breaker will do the same thing. I once spent $600 on a new strobe power supply only to find that a $20 breaker was old and had oxidized contacts. The mistake is easily made if one disconnects the power lead at the strobe's power supply and finds the voltage normal; the voltmeter draws only a few microamps and the voltage drop across the bad breaker therefore won't lower the reading enough to cause concern. Any voltage reading at the strobe should be taken with it connected and turned on. The large current draw will drop the voltage.

Dan