Strobe Repair - The Hidden Cost

[Daleandee]

Recently when taking my experimental plane over for the transponder certification as I was pushing against the tail to move it onto the maintenance area I cracked the lens for the tail mounted strobe. After returning home I changed the lens cap out and noticed the strobe wasn't working. I thought it was simply a bad bulb. After replacing the strobe bulb it still was not working.

Pulled the strobe fuse from the fuse panel and it was good. Removed the seat pan to get at the control box. The fuse on the box itself was good. Pulled the harness plug and was getting 12 volts to the plug with the switch on so ... the box must be bad.

Ordered a replacement strobe box, plugged it in and again ... no strobes. A further check found that I had 12 volts (12.8) at the fuse box, the panel switch, and the connecting plug as long as the box was not connected. Once connected the voltage went down to 3.22. I should have tested that earlier.

Now I believe it's a poor connection but where to find it? Took me and a friend a number of hours to chase down and finally locate a poor connector on the power line from the fuse box to the switch located at the switch. It appeared to be a good crimp on a quality Faston connector using Tefzel wire and covered with heat shrink. But for some reason it was causing a resistance that was dropping the voltage under load. It had worked flawlessly for over eight years.

I'm glad I found the problem and repaired it but not happy with myself because in my troubleshooting methods I made a few errors and assumptions that cost me time and money. But, the airplane is ready to go again and I can't undo what is done so the next best thing is to pass along an experience that might help someone else.

 

[Ed Haywood]

IMO the plane was telling you it wanted an LED upgrade.

 

[Bill Watson]

Not sure you really did anything wrong in your PD. Sometimes it’s just not that easy. I’m guessing that this is where good A&Ps either benefit from their experience or get beat up by disgruntled owners.

I had almost exactly the same problem though I can’t remember how fast I was able to track it down but had saved the burned out crimp-on connector and probably have a pic of it somewhere.

At one point, I probably thought the strobe control box was the problem and went shopping for a new unit. Not being limited to aviation units, or even units marketed to the experimental aviation market, I found that there are a variety of units sold for emergency vehicle use and, guess what; they are cheaper than the even the experimental aviation units despite similar being of similar configuration and design.

One difference between my original unit and the very similar replacement unit is that the power did not have to be run through the switch. Instead a power line could be run directly to the unit and a separate switching circuit could be run to the panel. Since the unit was installed next to the battery behind the baggage area in the RV10, that seemed like the way to go. Especially since I had noticed that the switched power line got noticeably hot during operation. Non-LED strobe installations require a lot of power.

So there is a perfectly good strobe unit sitting on my shelf and a burned out crimp-on floating around the shop while the RV10 strobe unit installation has been upgraded.

Long Live Experimental Aviation!


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[Daleandee]

IMO the plane was telling you it wanted an LED upgrade.

Yep, I got the idea that is what she wanted. But when I showed her the checkbook balance she was OK with what she had as I told her she could have new lights but that would cut into the fuel budget and she would have to stay in the hangar more ...

 

[Daleandee]

Not sure you really did anything wrong in your PD. Sometimes it’s just not that easy.

Thanks for the vote of confidence. I guess it's like bouncing a landing. You know with a little more attention to detail you might have done better but once it's done then it's over and needs to be forgotten. Lesson learned.

Not being limited to aviation units, or even units marketed to the experimental aviation market, I found that there are a variety of units sold for emergency vehicle use and, guess what; they are cheaper than the even the experimental aviation units despite similar being of similar configuration and design.

This is true. The strobe unit I have is from a state vehicle (commonly used on school buses). It has two strobes that double flash (one bright flash and another immediately following that is not quite as intense as the first) and the box itself is almost indestructible as are the bulbs that come with it. I used a 5 amp fuse in the fuse box but the unit itself is protected with a 4 amp from the factory so while they aren't as efficient as LED strobes they aren't too bad for power usage.

So there is a perfectly good strobe unit sitting on my shelf and a burned out crimp-on floating around the shop while the RV10 strobe unit installation has been upgraded.

A friend asked about purchasing the replacement box I ordered and I have considered it but I currently have a tail tip and a belly strobe. I have contemplated using the other box for wing tip strobes to go with what I have now. Along with the wig-wag landing lights they should see me coming ...

Long Live Experimental Aviation!

Agreed!