I've been in the process of resurrecting my Dad's Seneca II and we are almost ready to get it in the air. We were testing the lights and found that the beacon on the tail works from a split switch. When you turn on half the switch the tail beacon comes on. When you turn on the other half of the switch the wing tip strobes come on but the tail beacon goes off. Is this normal? I can't find anything in the POH or maintanence manual. I found the wiring schematic and it looks like that maybe both beacon and strobe should be on together. The switch is such that you can't turn off the beacon half with strobe half on.

Any help appreciated.

Michael

I would think that they remain on together. I would look for a bad ground on the switch or one of the devices.

There have been a couple of different iterations of both lighting requirements and how Piper wired the switches. So who knows.

I used to own a Seneca II. They should work as expected, with each half switch controlling the associated light.

I would suspect that the switch has been miswired at some point. They should function as independent but I’d guess someone put them in series by mistake.

The arrangement sounds identical to our PA-28s where there is a single strobe power supply that controls all 3 flash tubes. In that installation 1 pin at the power supply goes hot to turn the tail beacon on and the other half of the split switch makes a circuit between the pins labeled 'trigger selection' to activate the wing tips. If all the switching works correctly then maybe the problem is with the power supply?

Yeah, was trying to remember exactly how this was supposed to work. The switch is mechanically blocked, so that you can get all-off, beacon-on or beacon+tips-on. There should be no means to select tips only.

I'd concur with the other post, it may likely be the strobe power supply itself. It should be under the center-row seats. Should be able to quickly sort it out from there with a voltmeter and the Whelen diagram for how the strobe power pack is supposed to work.

If there's a chance that the waterfall panel has been off, there's a chance that someone has messed up the wiring. I ran into that myself on a couple of occasions.

Here’s the Seneca II diagram.