No Power - Surprise Alternator Replacement

When I stepped back outside, something definitely felt off. First clue: no water on the driveway. With the AC running, I should have seen a nice puddle from the evaporator core. Second clue: the 4Runner wasn’t even running anymore. My first thought? Alternator. But before throwing a few hundred bucks at a hunch, I figured a little troubleshooting might save the day.

I pulled out the jumper cables and hooked up my wife’s car to give the battery a boost. Voltage looked solid, so I restarted the 4Runner and tested again—this time, pulling the positive lead. The voltage dropped fast, from 12V down to 8V in seconds. At that point, the verdict was clear: off to the parts store for a new alternator.

Lucky break—the parts store had exactly one alternator left. Not so lucky? It was a remanufactured brand I’d never heard of. Still, I grabbed it because work waits for no one, and I’d need the 4Runner up and running by morning.

The swap itself was straightforward. First, I pulled the battery to get some room to maneuver, then loosened a few bolts, removed the belt and tensioner, and disconnected the wires. Swapped the alternator, then reversed the process to button everything up. As I worked, I noticed the old alternator looked original—probably the same one that’s been under the hood since day one. Part of me hated swapping it out for junk, but after 25 years and 163,000 miles, she’d earned a little rest.

With the new alternator in place, I fired her up, and this time the engine held steady. No mystery noises, and the voltage was holding like a champ. I let her idle a while, just to be sure, then took her around the block for good measure.

So, what’s next? After a bit of digging, I found out these Ultima alternators have a 20% failure rate—not exactly inspiring confidence. Picking up a spare might not be a bad idea. On top of that, I noticed the switch for my under-hood LEDs was rusted out. I pulled it, but it’s going to need some extra work to get it back in shape.