Testing Battery/Starting/Charging Systems Webinar: The Trainer Series

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Duration: 15 minutes and 54 seconds

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Not too long ago, I got a call late in the evening from my youngest son's girlfriend. Her Ford Explorer wouldn't start, she said, and could I please come and help? What was I going to do, say no?
 
I grabbed a meter and some basic tools and drove over to see what the problem was. It didn't take long to discover that the negative battery cable end had been replaced with one of those aftermarket clamp-style ends and it was spinning freely on the battery's ground post, a classic case of voltage drop. The connection was enough to allow the lights to work, but as soon as the high current demand from the starter tried to make its way through, the connection gave up and went open. I removed the clamp and cleaned the connection, then reattached the cable to the battery and tightened it up. She started the truck right up and I told her to stop by the next day so I could make a more permanent repair and check out the rest of the system.
 
Did she listen? Of course, not...she's a kid.
 
The next night I got another call from her, with the same complaint. Only this time the fault wasn't a matter of voltage drop but of voltage period. When I arrived the battery only read 8.64 volts, nowhere near enough to start the Ford's 4.0-liter engine. Heck, not enough to start my lawn mower's engine! But why is there a problem with the battery now, just a day later, when the truck started fine last night and all during the day?a
 
When you have a problem with the "no crank" or "slow crank", you need to make sure you test both the battery and starting system to see where the culprit lies. And if the battery is weak, you need to know why. Is there a problem with excessive resistance in the cables, like I had the first night? Is the charging system doing its job to keep the battery healthy? Or did the battery just die of old age or neglect?