Switch light behavior

tomkk · #1 03-24-2015, 03:31 PM

When I turn on the MASTER switch, the AVIONICS switch light is lighted regardless of whether the AVIONICS switch is on or off. With the NAV/NAV STROBE switch, both lights light regardless of whether the switch is in the NAV or NAV STROBE position. All other switch lights work as expected, the dimmer works correctly on all lights and the Switch & Fuse module seems to be functionally working correctly.

Could this possibly be the designed behavior? I'm looking at the schematics I downloaded and, I'm not sure I'm interpreting them correctly but, it looks like the AVIONICS switch light gets its power through pin 1 which looks like gets power whenever the EFIS is powered, that is, whenever the MASTER is on. Looking at the schematics for the NAV/NAV STROBE switch, it looks like pins 1 & 2 are tied together which means that both will light whenever one does.

Two separate Switch & Fuse modules have exhibited the exact same behavior.

DBRuth · #2 03-24-2015, 06:16 PM

My avionics switch light comes on when Skyview boots up regardless of position. Everything else works normally, nav/strobes, landing lite. Sounds like this is normal operation. I rechecked all connections to be sure it wasn't something I did to cause it.

tomkk · #3 03-24-2015, 07:04 PM

Thanks, Doug. Sounds like your Avionics switch works like mine. My nav light switch is a three position switch: center off, up = NAV STROBE, down = NAV. Both lights are off in the center position, both lights are lit in either of the other two positions. Is that how yours works?

All other switches work as I'd expect: function active = light on, not active = light off. Really weird that these two would be different.

Mich48041 · #4 03-24-2015, 09:13 PM

Quote:

When I turn on the MASTER switch, the AVIONICS switch light is lighted regardless of whether the AVIONICS switch is on or off.

The light is always on because the avionics switch is being back-fed as explained in THIS POST. Van's is aware of this matter. A possible solution (pending Van's approval) is to remove the wire and pin from D-Sub location 2 of the AV-50001 and move it to location 4 of the AV-50001.

tomkk · #5 03-25-2015, 06:08 AM

Quote:

Originally Posted by Mich48041

The light is always on because the avionics switch is being back-fed as explained in THIS POST. Van's is aware of this matter. A possible solution (pending Van's approval) is to remove wire P521-18-30-WHT from pin 2 of the AV-50001 and splice it to wire P527-18-30-WHT very close to pin 3 of the AV-50001.

I do remember that post now that you mention it, I'd forgotten all about it.

Now all I have left is my NAV switch light problem. Still don't know if that's normal. Seems like it might be based on what I think I see in the schematic.

I've been corresponding with Van's support about all this. They didn't think my switch light behavior was normal and even sent me a replacement AV-50001 to try to fix the problem - it didn't.

Mich48041 · #6 03-25-2015, 09:52 AM

Quote:

Now all I have left is my NAV switch light problem. Still don't know if that's normal. Seems like it might be based on what I think I see in the schematic.

The Nav/Strobe switch lights work as designed. If you want the strobe light to come on only in the strobe position, then wiring changes will have to be made inside of the AV-50001.

tomkk · #7 03-25-2015, 10:46 AM

Quote:

Originally Posted by Mich48041

The Nav/Strobe switch lights work as designed. If you want the strobe light to come on only in the strobe position, then wiring changes will have to be made inside of the AV-50001.

OK, that's what it looked like to me as well. Seems odd that it would be designed so both switch lights would illuminate in either position rather than illuminate only the one whose function is selected but it is what it is. Thanks for the response.

Charlie12 · #8 04-10-2015, 05:30 PM

tomkk forwarded an email to me from Van's engineering. It says there is a design glitch on single EFIS panels due to a wiring decision made when accommodating dual EFIS displays. I did the corrective action today and it seems to work. Master switch goes green when on and avionics switch goes green only when on, which seems like the way it should be.

The fix is relatively easy since my avionics bay is currently open. Move one wire from pin 3 to pin 10 on the connector on the back of the switch panel.

Mich48041 · #9 04-11-2015, 12:29 PM

I recommend this wiring change whether you are concerned with the light behavior or not. The reason is that the wire that powers SV-D1000 pin 20 could get warm to the touch under certain conditions (Master SW on, Avionics SW off). Moving the wire on the back of AV-50001 from 3 to 10 will eliminate that possibility.
The way to remove a pin is to position the tool around the wire and push the
tool all of the way into the hole before gently pulling on the wire. If the
pin does not come out easily, then rotate the tool 30 degrees and try again.
Keep repeating until the wire comes out easily without pulling hard. Do not
pull the wire until the tool is bottomed out in the hole.

rvbuilder2002 · #10 04-12-2015, 02:48 PM

Quote:

Originally Posted by Mich48041

I recommend this wiring change whether you are concerned with the light behavior or not. The reason is that the wire that powers SV-D1000 pin 20 could get warm to the touch under certain conditions (Master SW on, Avionics SW off).

Not very likely.
The current requirements for the single wire (even if a backup battery is being charged) are well within the spec for the wire gauge used.

Making the change will resolve an unintended functionality of the switch indicator LEDs though.