Some more interresting material regarding ground straps:
Be suspicious of ground wires
Damage to ground wires is almost inevitable, even during a moderate collision causing $3,000 to $7,000 in damage. During the repair process, be sure to check your collision repair reference to make sure you know the location and connection points for all ground wires. When they are securely connected, the electrical path is well defined. On the other hand, any breach will cause the electricity to find the shortest, easiest, quickest path of least resistance. Particularly for electrical components or circuitry in close proximity to the radiator or heater'that path can involve the coolant itself.
If you have the occasion to check for electrolysis, use a digital voltmeter set for 12 volts. Attach one test lead to the negative battery post and insert the other test lead into the radiator's coolant, making sure the lead does not touch the filler neck or the core. Initially, you may see a surface charge that could be 0.7 volts or higher. It could take up to two minutes for this surface charge to dissipate. Only then will you be able to obtain an accurate reading. A voltage reading of 0.3 or higher indicates that stray current is finding its path to ground through the cooling system.
Cooling fans and A/C-heater fans are logical sources to check and eliminate early in your diagnostic process. Then check any non-factory accessories that have been added. Next, you can turn the ignition to the run position while turning various accessories on and off. When the meter's voltage jumps, you've found the circuit with a bad ground. A small amount of electricity normally flows through a vehicle's cooling system. In a properly grounded system, this small charge (less than 0.3V) is constantly discharged and no harm is done.
Serious problems with stray-current electrolysis can occur when the cooling system is not grounded or when an ungrounded electrical device is part of the vehicle's operating system. The cooling system then becomes a warehouse for this stray electricity, and the coolant turns into an electrolyte. This charged coolant is constantly searching for a ground or a way out of the system. When it finds a material it can attack (the path of least resistance), the coolant goes to work 'eating through' that material radiator and/or heater causing damage such as the following:
- Solder-joint destruction
- Aluminum corrosion and flake formation that clogs the system
- Cast-iron corrosion that causes rust to contaminate the cooling system
Stray current also can be a problem with new, straight-from-the-factory vehicles. Back in 1986, Ford recalled approximately 19,400 vehicles to find a misrouted battery cable that could send a low-grade electrical current through the radiator, setting up an electrolytic action that could promptly ruin the radiator.
Frequently, by the time your customer realizes electrolysis is taking place, the radiator or heater damage is already done. Unlike a radio that frequently hums when a short exists or a resistor malfunctions, the cooling system does not emit an audible sound. To make sure that electrolysis doesn't start in your shop, let your technicians know the importance of reconnecting all ground wires.
What the future holds
For sure, you and your technicians will see more, increasingly complex electrical components and circuits in the vehicles that are brought to your shop for collision repair. As the price of mass-produced technology declines and consumer demand for convenience increases, the world of the possible will continue coming to the automotive industry. Many other ideas that are common in the aerospace industry remain to be transferred to automotive applications.
Soon water pumps will be electrically driven. Hybrid electric cars are already here. Battery-powered vehicles are on the horizon. These vehicles already operate at higher voltages and carry warnings about possible electrocution. A near-term change using existing technology is the 42V electrical system. Any electrolysis problems are likely to be the same, but the higher voltage is a good bet to cause larger and/or faster problems.
Tune in to new developments and stay current with diagnostic tools and procedures. Proper electrical grounding is just one of the many facets of collision repair that you need to know. Lack of knowledge is no ground for returning your customers' vehicles with incomplete repairs and easily avoided radiator and/or heater failures caused by electrolysis.