Service difficulty report · Light · Cessna 172M

Difficulty date
September 18, 2001
Submitted
March 13, 2002
Operation
General aviation
Aircraft
N1368U
Make and model
Cessna 172M
Aircraft serial
17267039
Engine
Lyc O320*
Part
Light
Part number
PQ876SW
Condition
Shorted
Location
Cockpit
Stage of operation
IN
How discovered
C
Nature of condition
L
Precautionary procedure
K

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

THE PART WAS INSTALLED AROUND THE TACH AND CONNECTED TO THE RHEOSTAT FOR THE INSTRUMENT LIGHTS. AFTER A COUPLE OF YEARS IT SHORTED OUT THE SYSTEM. IT BURNED OUT THE RHEOSTAT S2091-5 AND THE POWER TRANSISTOR 2N3055. THIS CAUSED NO INSTRUMENT LIGHT IN THE AIRCRAFT. THIS HAPPENED IN THE DAY TIME AND NOT AT NIGHT IFR. THE OWNER NOTICED NO LIGHTS AND NOTIFIED HIS TECHNICIAN. AFTER TROUBLESHOOTING THE SYSTEM HE FOUND THAT THE WIRES ON THE TOP OF THE LITE RING WERE TOUCHING ONE ANOTHER, CAUSING A DIRECT SHORT. CALLED MFG, THEY INQUIRED, WHEN THIS RING WAS INSTALLED. THEY SAID TO REMOVE IT FROM THE AIRCRAFT AND SEND IT BACK TO THEM, THEY WOULD REPLACE IT FREE OF CHARGE, BECAUSE THIS IS AN OLD STYLE RING.

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