The average car these days has 20 or more onboard computers. By crossing wires - connecting a positive cable to a negative terminal, or vice versa - you’re going to cause an electrical short that could instantly fry some of those computers. You may not find out the damage until your radio doesn’t work or your power windows don’t work. This could be an expensive repair. Perhaps the damaged microprocessor costs only $100 but it could take a couple hundred more to figure out what is wrong.
On the more extreme end, crossing wires could even explode a battery, St. Aubin said. If someone is standing too close to such an explosion, they could be seriously injured.
Jump starting a vehicle is a simple procedure but only works if it done completely correctly. Read below for directions on how to jump start a vehicle.
Safety Tip: The vehicle with the good battery should NOT be running when you are jumping and starting another car.
You are merely starting the dead car using another person’s battery. It is much more dangerous to have the car with the good battery running while performing this operation.
Tips for proper jumping
- Make sure the car that is being used with the good battery is TURNED OFF.
- If jumping in a dangerous place, move each car to a safer location.
- If possible, the cars should be parked side by side, not nose to nose. A car may lurch forward when it is jump started, so avoid standing in its path.
- Someone should be watching for any cars traveling too fast within a reasonable range of operation.
- Connect the cables in parallel (positive to positive & negative to negative).
- Start the car with the dead battery.
- Take the cables clamps off of each battery one at a time, making sure the clamps don’t touch.