Warning: Don't trust factory wire labels on old King Air panels

I spent two days chasing a bad compass reading on a 1980 King Air C90 because I trusted the factory wire labels. Turns out someone swapped pin 3 and pin 4 on the connector during a repair back in 2003. I had to tone out every single wire from the panel to the tail before I found it. Comparing a labeled wire to a toned wire showed the labels were completely wrong on 4 different pins. Now I tone everything myself before I touch any repairs on older planes. Anyone else run into mislabeled wires that cost you a weekend?

3 comments

3 Comments

ryanm601mo ago

Yeah that's the thing about trusting ANYTHING that's supposed to be "done right" in old systems. I've seen the same thing in my buddy's classic car resto - previous owners label wires with tape that falls off or they swap connectors and call it fixed. It's like buying a used house and trusting the previous owner's "professional" paint job. You ALWAYS gotta verify yourself. The older the machine the more likely someone half-assed a repair and moved on.

evan_cooper731mo ago

Buddy of mine found six mislabeled wires in a 1978 Baron after spending all weekend chasing an electrical fire. Said he about threw the whole harness out the hangar door.

barbara_grant41mo ago

You know, that's the thing about old Beechcrafts. Those 70s planes had some wiring that was basically a suggestion more than a diagram. I've seen harnesses where the color coding was done by whoever was working that day, and sometimes they just used whatever was left on the spool. Six mislabeled wires is a lot, but I bet if your buddy traced them all back, half of them were probably just swapped pin positions at the connector ends, not the actual wire itself. Still, chasing a fire like that... I don't blame him for wanting to just rip it all out.