Mustang MonthlyHow To Interior Electrical
Avoid This Mistake: Alternator Too Weak for the Application
Not having enough alternator for the application
Classic Mustangs had marginal charging systems when they were new with amperage output ratings ranging from 38-65 amps. Most remanufactured Autolite and Motorcraft 1G alternators are 65 amps these days. To add insult to injury, these classic charging systems are externally regulated by mechanical contact point voltage regulators, which can be hit and miss in terms of reliability. Lights flicker. Batteries run down. Frustration abounds. You may opt for a solid-state voltage regulator, which works quite well—that is if your alternator is delivering a solid 14-15 volts and all diodes are in working order.
How many years have we been mindlessly running these half century-old dynamos and the disappointment continues? The solution is a 100-130-amp single-wire Motorcraft 3G alternator. You can buy a new 100-plus amp Ford 3G alternator from Summit Racing Equipment and be back on the road in a matter of hours. A Powermaster 3G from Summit is perfect for your daily and weekend driver. Installation is easy to accomplish, however if you have an ammeter-equipped instrument panel, the ammeter must be bypassed with heavy gauge wire behind the instrument panel.
You must also pay attention to alternator output in a restomod build. Adding things like a high-watt stereo, electric fuel pump, EFI, and all the other modern electronics we like to install in our restomod Mustang projects all require amperage to run. Add up the amp draw from all of them, and get an alternator that can keep up. You can imagine driving your car at night, with the new HID headlights on bright, the stereo and A/C cranked to max, your phone charging, the fuel pump at full song, and the MSD box providing spark…that requires a pretty burly alternator to keep the battery from going dead.
The Motorcraft 3G internally regulated 100+ amp alternator is available from a number of sources including Performance Distributors and Summit Racing Equipment (Powermaster). This dynamo will keep up with your toughest electrical system demands and keep the battery charged. The 3G is a perfect fit to replace your classic 1G. Don’t forget to bypass your ammeter when you go with a one-wire alternator. Also note that a one-wire alternator usually requires the engine to rev over 2,000 rpm or so to “excite” it, meaning to get it working. Once it’s “on,” it’ll charge at idle, so the general rule is that when you first start the car, you have to rev it up to the manufacturer’s spec for just a second (we usually just wing the throttle) to get it charging.