Had a radio swap go sideways at KAPA last Thursday

I was out at Centennial Airport swapping a KX-155 for a new GNC 355 in a 172. Everything was going fine until I powered it up and the annunciator panel stayed dark. Turns out I missed a pinched wire behind the radio stack that was grounding out the whole bus. Took me two hours to trace it with a DMM. Has anyone else run into issues with those old Cessna wire bundles getting brittle near the firewall?

3 comments

3 Comments

barbara3992mo ago

Did you check the firewall for the hidden wire gremlins? Those old Cessna bundles are like dried spaghetti back there, I swear the plastic cracks if you look at it wrong. Last time I had one snap while swapping a tray I spent an hour rewiring a single pin just to get the clock to light up again. Nothing makes you feel smarter than cursing at a pinched wire that you definitely caused yourself.

william91712d ago

Actually that seat track screw thing reminds me of the time I found a dime wedged between two pins in the back of a Garmin 430. Must've been there for years, guy before me probably dropped it changing a fuse and just let it slide. Anyway I pulled the unit out to troubleshoot a ghost signal on the nav side and there it was, all tarnished and shorting out the whole com 2 line. Fixed the issue but then I had to recalibrate the heading because apparently I bumped the flux valve while I was back there. Took me another three hours to get it back to zero and I still think it reads about two degrees off on a good day.

holly_gonzalez612mo ago

Did you check if the old shield drain wires were rubbing against anything back there too? I had a similar deal last month with a 152 where the whole avionics bus went dead because a ground wire was chafed right where the bundle goes under the rear seat support. Ended up having to pull the entire interior carpet out to find it, turns out a loose screw from a previous seat track install was slowly wearing through the insulation. Made me want to just wrap the whole harness in duct tape and call it a day.