Alternators do lose capacity when aging.
Be aware that if electrical fans run, lights are on, maybe defogger is on, two fuel pumps running, and running at 600 rpm at a traffic light, your alternator may not be able to cope with the demand and the battery gets drained. Not so bad for a short moment, but the battery needs charging asap. Either by a proper charger or by a long stretch running over 2000 rpm and with normal power consumption (like fans off and defogger off).


78-86 alternator: 928.901.114.01: 90A /1260 Watt

87-95 alternator: 928.601.011.05: 115A / 1610 Watt



The '87 and later cars (with electric fans) are very marginal, in terms of current output. Add in a high power stereo, a higher current draw blower motor for the HVAC system, or one of my upgraded A/C systems and the charging system will have a tough time maintaining 12.5 volts, especially at night.

(The main reason I made this alternator was because the output of the stock alternator with my upgraded A/C system was very marginal....and the added load from my A/C system upgrade was less than 15 amps.)

The reality is that if the cable from the battery to the starter is good enough to crank the car over, it is good enough for 150 amps to go back the other way.

The cable from the alternator to the starter was sized for the current alternator (except in the late model cars, when they increased the size of the wire.) Most likely, any car with an original loom needs one of my supplementary wires. If you have a "replacement loom", inquire with the builder about the current capacity of the wire used.

The stock ground cable from the engine to the chassis is plenty adequate....when in good condition. Any of these original ground wires needs to be replaced.

The stock battery ground cable is marginal....even when brand new. That crimped on brass end at the chassis side is......problematic.

The majority of the cars I see sit for weeks, slowly draining the battery. When they are used, they are generally working on a very low battery....sometimes jumped to even start the cars.....or charged only enough to start the car.

The alternator is then expected to both run the car and bring the battery up to full charge....very rarely occurring. It's not uncommon to see 12.5 volts (or lower on a hot summer day with the A/C running.) Headlights are dim, sunroofs barely function, windows work slow, and the injection system on the late cars is VERY dependent on good voltage.....sometimes resulting in misfires.

Rarely, the battery achieves full charge before the cars are parked...starting the cycle all over again.

These cars respond much better, when they can make over 13.5 volts while running and still have enough capacity to charge the battery.

Everything works better......all of the electric motors love the proper voltage and the correct operating speeds.

greg brown