Landing Gear Lights-Need Wiring Help

[BG]

Hello,

I'm replacing the landing gear down indicator lights and the transition
light in a Lancair 235. The installed lights are the kind that snap into a
hole in the panel, and the bulb is not accessible without removing the
entire light fixture.

I'm replacing those with the push-to-test type of lights found on most
certified aircraft (MS25041). The advantage being that one can check a
non-illumnating light to determine wether the circuit is open, or the bulb
is bad. The bulb can also be replaced from within the cockpit.

The dilema I am having is how these lights wire up: There are three
terminals on the fixture Vs. two on the old ones.
One terminal in the center and two on the outer edges. If I wire the
center(+) and one of the outer edges(-) to the circuit the light comes on
when its supposed to. However, the light won't illuminate when the
push-to-test feature is used (light pushed in).

What does the un-used terminal get wired to? An always on supply (+)?
I'm afraid to try it for fear of shorting something out. I welcome any
advice from someone who has wired these up before.

thanks in advance,
Bill Gilbert
N235JR

[Morgans]

"BG" > wrote in message
news:7dx%a.1164$kP.156@fed1read03...
> Hello,
>
> I'm replacing the landing gear down indicator lights and the transition
> light in a Lancair 235. The installed lights are the kind that snap into a
> hole in the panel, and the bulb is not accessible without removing the
> entire light fixture.
>
> I'm replacing those with the push-to-test type of lights found on most
> certified aircraft (MS25041). The advantage being that one can check a
> non-illumnating light to determine wether the circuit is open, or the bulb
> is bad. The bulb can also be replaced from within the cockpit.
>
> The dilema I am having is how these lights wire up: There are three
> terminals on the fixture Vs. two on the old ones.
> One terminal in the center and two on the outer edges. If I wire the
> center(+) and one of the outer edges(-) to the circuit the light comes on
> when its supposed to. However, the light won't illuminate when the
> push-to-test feature is used (light pushed in).
>
> What does the un-used terminal get wired to? An always on supply (+)?
> I'm afraid to try it for fear of shorting something out. I welcome any
> advice from someone who has wired these up before.
>
> thanks in advance,
> Bill Gilbert
> N235JR
>
\

I've not installed one of these before, but what you need to do is check the
terminals with a volt ohm meter. Find out what is normaly open and normaly
closed, then go from there.

--
Jim in NC--

[BG]

"Morgans" > wrote in message
...
>
> >
> > I've not installed one of these before, but what you need to do is check
> the
> > terminals with a volt ohm meter. Find out what is normaly open and
> normaly
> > closed, then go from there.
> >
> > --
> > Jim in NC--
> >
> I should have included more detail. In the position that you are not
> pushing on it, find out which terminals pass the electricity through the
> bulb. Next, push the bulb, and find which terminals cause the juice to go
> through the bulb. Use the terminals that were not causing the bulb to
light
> in the un-pushed state, but lighting when you push it, for hooking to the
> always on (with master on), and the other terminals to the indicating
> circuit.
>
> Does that make any sense?
> --
> Jim in NC--
>
Yep, sure does.

That's what I thought; that the un-used terminal, when the light is on,
would have to be hooked up to a "live" curcuit.
Thanks for confirming my thought. I'll have to try it out next.
Actually, I just saw some lights in Aircraft Spruce that allow for bulb
replacement, but aren't push to test. Simpler to wire up and gives me the
light bulb check I need in case a gear light doesn't go on.

Bill G