Stray current

[YNOT]

modern radiators are vulnerable to stray current corrosion because many of them are attached to the
vehicle by their plastic tanks, or are insulated from the vehicle chassis by rubber mounts.
In many cases electrical cooling fans are mounted directly to the radiator frame. Fans and fan motors
cause lots of noise, vibration and harshness so they are insulated from the vehicle on rubber mountings.
Introduce some bad electrical contacts for the fan wiring and you have set the scene for rapid electrolysis
via the cooling fans.
The same fan is probably cycling more often because it can’t rotate quickly enough as it has a bad earth
contact. These are perfect conditions for disaster – lots of stray current, longer fan ON time and a hotter
engine. A copper/brass radiator will suffer stray current damage, too. However, an old copper/brass
radiator is usually bolted directly to the vehicle body work, providing an easy path to earth for any stray
current that finds its way into the cooling system.
Plastic tanks and rubber mounts deny any stray current an easy path to ground. The environment for
electrolysis in its most virulent form now exists.
Cooling fans are by no means the only cause of stray current problems. Stray current problems commonly occur following body repairs. The cause is over-spray. Paint
does not conduct electricity. Therefore, over-spray at an earth point forces the current to find an
alternative path to earth – the cooling system.
Corrosion damage in the areas of a radiator, while operating within a squeaky-clean cooling system, is
a pretty good indication of stray current damage.
In simple terms, stray current is a chemical/electrical process which causes an electrical current to pass
through a vehicle's cooling system fluid. It can cause rapid damage to radiators and will indirectly cause
problems with other engine components such as water pumps, thermostat housing etc.
It occurs when one or more electrical items, such as a cooling fan or headlight, develops a problem in
its electrical circuitry. This causes an electrical current to seek out an earth path via the radiator core
through the engine coolant.
Stray electrical current can destroy an aluminium or copper/brass radiator in record time.
Aluminium radiator cores have been known to fail within a matter of days, due to stray current.
Many manufacturers and radiator suppliers can refuse to honour a warranty where stray current
corrosion is found to be the cause of premature radiator failure.