Touch the battery ground of your car with the negative test probe of your volt/ohm meter, then carefully dip the positive test probe into the coolant in the radiator making sure it does not touch the filler neck. By doing this, you will test whether electrolysis has already occurred in you radiator before your next course of action.
Check both the AC and DC reading on the meter with the entire vehicle system turned off, other than stand-by systems in the vehicle such as automatic battery chargers.
Note the AC and DC readings on the meter with the starter engaged, and note it again with all your vehicle systems such as head lights, radios, coolers and air conditioners turned on. Readings above 0.2 volts on the volt/ohm meter means that you have a serious case of electrolysis that would damage your engine, while readings in the hundredths would not cause aluminum failure.
Determine the reading on the meter change whenever you turn on a system in the vehicle. If the reading rises when you turn on a system and drops when you turn it off, it means that you have type A electrolysis, which is caused by a faulty ground in the system. Isolating the system circuit then fixing its ground would prevent this type of electrolysis.
Check if the reading remains constant but above 0.2 volts when you turn on and off all the car systems. This means that your radiator is experiencing type B electrolysis, which is caused by chemical changes in the coolant but not induced by any external electric current. Getting rid of this type of electrolysis involves neutralizing the coolant that must have turned acidic to cause it. Remove and replace the used antifreeze and scrub the internal surfaces of the radiator.