Service difficulty report · Wire Harness · Cessna 172S

Difficulty date
February 24, 2008
Submitted
February 27, 2008
Operation
General aviation
Aircraft
N227BH
Make and model
Cessna 172S
Aircraft serial
172S10662
Aircraft time
6 hours
Engine
Lyc IO360L2A
Part
Wire Harness
Condition
Burned
Location
Instrument Panel
Part time
6 hours
Stage of operation
IN
How discovered
O
Nature of condition
B
Precautionary procedure
K

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

What was found

WIRING HARNESS BEHIND AUDIO PANEL WAS CHAFING ON BRACKET THAT HELPS SUPPORT STANDBY BATTERY ON THE PFD SIDE AND CAUSED WIRING TO ARC AND BURN (NOTE: HARNESS IS FOR LIGHT DIMMING OF G-1000). FOUND HARNESS PULLED HARD AGAINST BRACKET. THIS CAUSED THE WIRE TO CHAFE THROUGH THE INSTALLATION AND SHORT OUT. HOWEVER, CIRCUIT BREAKERS AND TRANSISTORS FOR THE LIGHT DIMMING CIRCUIT DID AT NO TIME POP OR FAIL AND WOULD EXPECT TO HAPPEN WHEN THEIR IS A HARD SHORT SINCE THE WIRES ARE ASSOCIATED WITH THE LIGHT DIMMING CIRCUIT. THE HARNESS WAS PULLED HARD AGAINST THE STRUCTURE AS TO CHAFE THROUGH THE INSULATION AND ARC/SCORCHED THE STRUCTURE. THE WIRE BURNED THROUGH AND ALSO, DAMAGED OTHER WIRES IN THE HARNESS. HARNESS WAS ALSO FOUND UNPROTECTED. WILL NEED TO INSPECT OTHER WIRES TO DETERMINE THE AMOUNT OF DAMAGE AND CORRECTIVE ACTION WILL BE REQUIRED. AC WAS DELIVERED 2/13/2008 AND HAD ONLY 6.3 HRS ON IT SINCE NEW.

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