This from the NARSA (Natl Automotive Radiator Service Assn):

NARSA OFFERS MOTORISTS TIPS TO AVOID
GETTING A CHARGE OUT OF ELECTROLYSIS
Experts Warn That Too Many Car Accessories Can Lead to Cooling System Damage

EAST GREENVILLE, Pa., March 2000 – Using multiple accessories, such as wireless phones, radar detectors and upgraded stereo systems on long trips may be hazardous to your car’s health, say experts at the National Automotive Radiator Service Association (NARSA).

Electrolysis is decomposition produced in an electrolyte by an electric current. In a vehicle, electrolysis refers to high levels of electric current in the coolant flowing through a system that results in decomposition of the soldered joints on the tubes of the heater core. While a minor electric charge (less than 0.1) occurs naturally in all cooling systems, in vehicles with missing or incorrectly placed grounds, having multiple accessories plugged in or turned on over the course of a long trip can lead to trouble.

“An increased electrolysis level can cause metal components in the cooling system to corrode,” says Don Hart, NARSA president and Texas shop owner. “It can also lead to an electrochemical reaction that could create holes in cooling system hoses.”

The best way to find out if there are high levels of electrolysis in your vehicle’s cooling system is to have the system checked by a specialist. After running the vehicle’s engine and accessories, the technician will run a static electrolysis test and examine all hoses, belts and the heater core for leaks and signs of deterioration.