Re: What's the down side of "positive ground system"?
glemon said:
Worst issue I had is when I tried to wire and isolate a negative ground stereo in a positive ground MGB (many many years ago, I will add). Ended up with lots of burnt wire and smoke, somehow didn't fry the radio though.
Long time ago, a friend and I took a 3000 mile road trip, he in his MGA & I in my TR3A. To stay in touch during the trip, we both temporarily installed CB radios. He clamped the antenna onto the back bumper, wired positive to positive and away we went.
2nd day on the road, his dash suddenly erupted in smoke. Fortunately he had left the battery cover and one battery clamp loose, so it only took a few seconds to disconnect the battery. Sure did make a mess out of the wiring under the hood, though!
Obvious in retrospect, but neither of us realized it beforehand ... his CB had the antenna clamp grounded to the negative lead. Apparently, it had worked at first because the bumper mounts were so rusty that they didn't conduct; eventually the vibration must have lead to a good connection and formed a dead short through the antenna shield. The radio had a fuse, but of course it was in the "hot" lead so didn't blow.
That was a fun trip! We picked apart the bundle of fused wires, robbed a wire from somewhere (wiper motor IIRC, who needs those) to power the coil, and continued on.