COUGARNFW wrote:
: Nobody looks it up. The 4522 lamp is usually used in a swing-down lamp. The
: swing down lamp has a motor to drive the lamp up or down.

: The lamp is 12 volt, 250 watt, something the guesser at 9 amps (if for a 24
: volt plane) would have realized if the system voltage of the plane had been
: given, so the current draw for the lamp along is a nominal 20 amps.

: If the motor circuit is not opened by the switch/relay built into the light,
: the combination of the lamp current and the motor current will pop the breaker
: every time, in a short time.

: Yes, check the amps with a current meter, and please do not let the motor run
: long in the test or it will burn out.

: Neal

Correct... I wouldn't even go around shaking the wire, etc, checking for
chafing until I measured the current. It's awfully easy to put in a bigger bulb "more
is better" and all. A friend's Comanche had had two landing lights installed that
were *both* 250W (14v plane). That would require a 40A breaker... rather insane.
Some boob had put the wrong bulb in it, because each was supposed to be a 90W bulb
(125W? I don't recall exactly, but not 250).

Disconnect the wire at the breaker, insert ammeter, and then read the current
with and without the engine running. The change from the bulb running on 12V/24V
(engine off) to 14V/28V (engine on) makes a significant difference in current. There
should be plenty of margin on the breaker (e.g. taking 10A on a 15A breaker).
Breakers do drift a bit with age and typically can blow easier than when new. If it
is the correct bulb and within spec of the breaker, THEN look for worn wires and/or
weak breaker. Replacing the wire as the first thing is silly and a lot of potentially
unnecesary work.

-Cory
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* Cory Papenfuss *
* Electrical Engineering Ph.D. Graduate Student *
* Virginia Polytechnic Institute and State University *
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