ARGH!! How did this happen??

SO, I wired my panel with a cigarette lighter yesterday. Red wire got the juice and black was grounded to the airframe. The ground for the cigarette lighter terminted at the same place as the ground for the master, electric T&B instrument and one other item I cant recall as I type this. After install, I turned on the master and stuck a voltmeter on the cigarette lighter socket and it read 11 volts.

While I was at it, I wired up my WxWorx box. Red wire got the power and black was connected to a ground wire which terminated at a different place than the cigarette lighter. I then connected the GPS and the Wxworx box with the wxworx supplied connector.

Then, I inserted my GPS cigarette lighter power cord into the socket and flipped my master switch on.....My GPS made some crackling sounds from the speaker and would not power up. I unplugged the GPS and tried to turn it on my itself but to no avail...I think its dead.

How in the world did this happen? Did I wire something incorrectly?

Some cheaper 12V accy sockets can short out internally when you plug something in to them. Was accy socket fused and what size? What gps do you have? Was gps lead fused properly? Recheck all grounds.

I know the lighter socket is fused and the GPS lighter cord is fused too. Neither fuse blew. I dont know what size fuses they are off the top of my head. I have (had) a AvMap GeoPilot II Plus.

Battery leads reversed?

Low voltage maybe

Maybe 11 volts is too low for the gps to come on. Or the cable has an open wire connection. You should be able to check this with your VOM.

Sanity Check ?

Have you tried the lighter in your car as a cross check? You should also be able to stick the positive lead of a volt meter down the center of the cig lighter plug, the other side to the airframe and see a positive voltage reading.

Further investigation..

I tried plugging the GPS into my car's cigarette lighter and no joy...wouldn't come on. I went back out to the airplane this morning and turned my master on and realized my Wxworx box is fried too. It wont power up. It was tied to the GPS during yesterday's events.

So, I went to check my ground wire to the cigarette lighter and somehow I had some wire insulation wedged between the ground post and the ground wire. I removed the FOD and retightened the ground post. To check things out, I plugged my cell phone into the cigarette lighter and it appeared to charged normally.

Do you think a poor ground connection would fry my GPS and wxworx? I would have thought it simply would not have turned on because the circuit wasnt completed.

blueflyer said:

Do you think a poor ground connection would fry my GPS and wxworx? I would have thought it simply would not have turned on because the circuit wasnt completed.

Click to expand...

My suspicion here is that the current found an alternate way to ground, and that was through your instruments, thus both of them being fried.

Check for a fuse inside the cigarette lighter plug, some of them have an internal fuse.

Alternate path

Perhaps the lost ground shifted the current through the Wxworx unit but I find it somewhat unlikely that would damage both units. Were you doing any other work around the alternator or battery? Reverse voltage or over voltage sound more possible. Is it a dual battery setup?

Easy fix?

Any chance your fried units are internally fused? Some electronic components are internally protected against Electron-Challenged individuals pretending they can wire.

Not saying your are one of them.

Just don't ask me how I know this!

single battery source and no other eletrical work being done at the time. Im beginning to believe what Mike said. The faulty ground found an alternate path through unwanted places.

Im going to crack open my GPS and wxworkx and look for an internal fuse. I hope to find them both blown!

And yes, I am severely electrically handicapped and the learning curve is steep and expensive.

quick update: I found a skinned wire on my power into the cigarette lighter. I guess it was shorting out there. I fixed that and saw 12 volts on my meter (I guess the previous 11 volt reading was telling me something I didn't know how to interpret.....now I know for next time). I decided my fried electronic gadget were just lessons learned. I was already pricing the 696. But, I plugged the GPS and Wxworx box back up to ship power for giggles and IT ALL FREAKING WORKS....better lucky than good I guess. Thanks for all the help.