A 4522 lamp is a PAR46 bulb, 13 volts 250 watts 290,000 cp
5.75 inch dia with a rated life of 25 hours. 250w/13v = 19.23 amps
If it runs at more than 13 volts it will draw more current and burn
out quicker.

A 20 amp breaker is running very close to its limit powering this
lamp. Since these breakers are thermal breakers a poor crimp or a
loose screw on the breaker terminals will cause extra heating and
cause the breaker to trip at lower than 20 amps. As these breakers age
they trip at lower than rated current due to oxide build up on the
internal contacts.

The next smaller wattage in the same lamp shell size, PAR 46, is a
4537. This is rated at 100 watts 13v, 200,000 cp

My 172M uses two 4905 lamps at 100 watts each which are PAR 36. These
are a smaller diameter lamp and will NOT fit in t PAR46 mount.

Look for hot crimps on the breaker wires and chafed wires going to the
lamp.

On 22 Aug 2004 21:59:44 GMT, (Hankal) wrote:

I suspect someone installed the wrong lamp in your aircraft. Many
14volt 172's use a par36, 4509 lamp which is rated at 13 volts, 100
watts, 7.7amps.

You need to look up in the parts list for the aircraft the correct
part number of the lamp.

I did look at the parts manual and it states GE 4522 and the breaker is a 20
amp.
Would a 4509 or 4905 fit in the same housing?
Hank