You’ve got questions. We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re troubleshooting a weak charging system.
J.W. Dix Hills, NY
Q: I own a 1969 Ford Bronco which I am rebuilding to near race standards. I have completely rewired the truck and have come across a snag. For some reason I cannot make the charging system work properly. I have a new 65-amp alternator, new starter solenoid and voltage regulator, MSD box and coil, and ACCEL distributor. With the truck running, the voltmeter continues to go down. It goes down very slowly (quicker with the lights on) but is always in discharge mode. If left alone, the battery would run down while driving.
My battery has been absolutely abused—discharged a few times, left uncharged for two months, and cranked without recharging while I was doing engine work. Could the problem simply be that my battery is shot and will no longer hold a charge?
A: There is a good chance the battery has gone south. The acid in it can deteriorate the lead plates and cause them to short internally. Charging the battery and load testing it in relation to its cold-cranking amps will show the battery’s condition, but sometimes after charging it will hold only a surface charge that allows it to pass a load test. Letting it sit for two or three days after charging and then load testing will give you a much better reading of its condition.
Testing the charging system will require a volt and amp meter capable of putting a load on the system. Readings at the battery should be between 13.5 to 14.5 volts and 55 to 60 amps under load. If these readings are low, it is possible the alternator or regulator are bad. It is also possible that a wiring problem could be causing it. At this point, you’ll need to hunt down a wiring diagram for your Bronco so you can trace the wiring.