sbteter

'02 f150 ...just got new battery after son's gfriend charged the old one overnite but with reversed cables/polarity.Now ignition switch won't start engine but a screwdriver laid across relay leads will. Do I need a new ignition?

BareBonesXL

Might be a blown fuse or fusible link. Check those first. And see if there's anything else that's not working. Might be a clue. The ignition switch won't care which way the current flows, so that seems unlikely.

JCR 56

Maybe the relay is bad.

ProjectSHO89

Too many variables, not enough details provided.

NFortin1966

When the battery was hooked to the charger incorrectly, was it still in the vehicle? Were the vehicle cables connected or disconnected when charging? If they were still connected, then the ECM could have been damaged.

BareBonesXL

You probably should have wrote "was", Bad relay might have been the original problem. The charger and the new battery are distractions.

Maybe why he hasn't been back. Most of today's chargers, even the cheap ones, will sense or trip when the polarity is wrong. Connecting the battery backward is one thing, but connecting the charger backward just trips the charger.

Sounding like dead battery wasn't the original problem. My first post was thinking along the lines of backward battery connection. But his post says backward charger.