Why did my electricity fail after jump starting another car?

Dear Car Talk

Dear Car Talk | Sep 01, 1989

Dear Tom and Ray:

One cold winter night I pulled into a parking lot with my 1973 Pontiac LeMans. Before I shut down the engine, somebody asked for a jump start. Me being the nice guy that I am, and she being of the opposite sex, I jump started her car. Then I disconnected the cables and shut off my car. Three hours later, my car started right up, but I had no lights, no heater, no radio, nothing electrical! I followed a friend home, since I had no lights, and about ten minutes down the road, everything came back on. What happened?

TOM: There are two cables attached to the negative battery terminal of your LeMans. One goes to the engine block and acts as a ground for the starter motor. The other grounds everything else. In your distracted euphoria, you accidentally disturbed that second wire and loosened the connection. Some benevolent bump on your drive home was enough to jar the connection back into place. If the connection is that precarious, get it fixed. Next time you may not be so lucky.

RAY: And in the future, Frank, pay closer attention to what's really important...get her phone number.

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One