Stop treating all battery issues like they’re created the same
April 1, 2001
In any weather, poorly maintained batteries and electrical systems can create problems affecting starting systems.Often, the culprit is judged to be an apparently dead battery, when, in fact, the prim...
In any weather, poorly maintained batteries and electrical systems can create problems affecting starting systems.
Often, the culprit is judged to be an apparently dead battery, when, in fact, the prime cause is a faulty charging system. So, simply replacing the battery or batteries without carefully checking the electrical system is a short-term cure, at best.
Charging system problems should be suspected when your vehicle refuses to start – the battery will have discharged and the starter will not crank the engine.
At that point, your first step is to test the battery and replace it if necessary. To accurately measure system voltage, bleed the surface charge from the battery by turning on the headlights for one minute. Employ a good quality digital multimeter and measure the voltage across the battery terminals with the lights off.
Remember, however, voltage tests only tell the state of charge, not the battery condition. This is commonly known as a “load test.”
If the battery is charged and passes a load test, then look for resistance in the starter circuit, providing the engine is still slowly cranking. Check for excessive current draw, signs of worn insulation on the wiring, or a faulty starter. Even only slight resistance will create a low voltage situation.
In a starter system drawing 200 amps, for example, as little as 0.01 ohms resistance in the starter cable will cause a two volt drop at the starter.
Therefore, based on Ohms Law, you have 0.005 Ohms resistance, which is too high. Clean the connection; high resistance among grounds can produce bizarre symptoms that often don’t seem to have anything to do with the cause.
Lights that glow dimly, lights that come on at the wrong time, gauges that change when the headlights are turned on, or lights that don’t come on at all, may all become evident. Always pay particular attention to ground terminals in the vicinity of the battery, where acid will often speed corrosion.
Current drains, shorts and bad grounds are the cause of many problems. Current drains that run the battery dead are often referred to as shorts, although they may not actually be short circuits.
In fact, they may be related to electrical systems that require continuous power.
One example would be an electronic control module (ECM) found on any modern heavy-duty engine. Some of the units’ internal components are designed to retain informational memory, and thus draw battery power continuously.
Shorts that blow fuses (or trip circuit breakers) can be found by using the same troubleshooting techniques used to find current drains even though the symptoms are different.
Using the wrong testing method can exhibit erroneous results, therefore you should always refer to the vehicle OEM’s service procedures.
If a “jump” is the only way to get you going until you get a chance to inspect the vehicle electrical system, follow this procedure.
While most of you have likely had the opportunity to jump start a dead battery before, how many of you have done it safely?
Consider these recommendations:
Since batteries contain explosive gases, never strike a match while jump starting and inspect to ensure you don’t boost a damaged battery.
Batteries contain sulfuric acid, so if any happens to get on your skin, or in your eyes, flush with water right away and then get medical help immediately.
Wear eye protection with side shields, or glasses with a face shield whenever possible. Alternatively, wear a pair of eye goggles.
Avoid leaning over the battery when connecting and disconnecting the booster cable clamps.
Make certain that the vehicles are not touching, and that both ignition switches are in the off position.
In this order, connect the positive booster cable clamp to the positive terminal of the discharged battery. Then the other end of the positive cable to the positive terminal of the good battery. Connect the negative cable clamp to the negative terminal of the battery in the starting vehicle. And, this is where it can get tricky, make the final connection to the engine block of the dead vehicle. This minimizes the circuit resistance and avoids potential arching, which could blowup the battery.
Ensure that the booster cables are well clear of rotating fan blades, belts and pulleys.
Stand clear of the engine and batteries whenever possible.
Start the vehicle. If the dead vehicle does not start, wait approximately 30 seconds before trying again. This allows the starter motor to cool off. By the same token, do not crank for longer than 30 seconds continuously. Many heavy-duty trucks are equipped with a starter motor thermostatic switch that will prevent engaging the starter after it becomes too hot from repeated starting attempts.
So you may find yourself waiting two minutes before the starter can be engaged if you try to rush.
To remove the booster cables, reverse the order above. n