With the engine running, check the output at the back of the alternator and see if it’s th
Whether it’s a ground-up, refurbish, or a search and repair mission on your latest project, tracking down electrical problems don’t have to be an unsolvable mystery. We found ourselves having some minor, albeit annoying, electrical woes with our ’62 Chevy and thought before getting too deep into any upgrades we’d start by diagnosing the electrical system.
Our ’62 was converted from a generator to a 60-amp alternator somewhere in its life. From the time we bought the car it would display slow cranking characteristics. After we installed electric fans the slow cranking problem persisted, even worse. You know the sound and the feeling; “Oh no it’s not going to start.” We figured a bad battery was too obvious, but that’s where we started. It’s surprising how many times the problem isn’t the battery but another link in the electrical system. That’s not to say a battery can’t go bad but often it gives up the ghost because other electrical system woes inflict abuse on the battery.
Since nothing in the electrical system can tell you “how they are feeling” you need to get out the equipment and give the system a once over. There are simple and sophisticated pieces of test equipment available for any hot rodder to use and oftentimes solve your own problems. If not, you can take the route of a professional mechanic who is qualified to analyze electrical systems. It will also be helpful if you can provide as much data as possible, such as one of the taillights isn’t shining brightly, the ground strap is missing from the engine to the chassis, etc. This additional data is very helpful in finding the faulty component and the root cause. Remember you need to fix both the cause and the faulty component.
Next, check the voltage at the battery; it should be the same as the alternator output. If
In checking our Chevy we found that while our battery and alternator were in good condition they weren’t the capacity that was now required. As is often the case accessories were installed, such as stereo and electrical fans, without any consideration for the additional electrical load.
To begin our project we visited Rudy Renka of Rudy’s Garage (Costa Mesa, CA) whose shop is near the magazine. He has helped us for years with our stockers and from time to time we bring in our hot rod projects. A longtime drag racer, he gets what we are doing and how it should be done.
After he tested our Chevy he found that our 600 CCA battery needed to be replaced with an 800 CCA battery, so in went a new Optima and a fresh battery tray from Trans-Dapt. He also found the alternator charge line that ran to the battery wasn’t a large enough gauge wire; it needed to be a 10-gauge wire wrapped in Trans-Dapt flexible wire harness tubing for protection. We took out a voltmeter and determined that the improper gauge wire resulted in a voltage drop. We were experiencing a voltage drop (1.4 V on the positive side of the battery and a 0.25V drop on the negative side of the battery). Ideally it should have shown a draw of 0 V. During the cranking process the old charging system would show a voltage drop of 0.75 V on the positive side of the battery and a 0.8 V on the negative side. The battery also produced 175 amps on cold cranking and 190 amps on hot cranking.