LED Bulbs in Classic Cars: Lessons From My Fleet

When I first tried LED bulbs, I hated them. Flickering, early failures, weird color — they just weren’t worth the hassle. But with two low-output alternators in my fleet (a 1969 MGB GT and a Honda Acty kei truck), I had no choice but to try again. This time, the results completely changed my mind.

Why I Used to Avoid LEDs

For years, I stuck with incandescent bulbs. Every LED I tried seemed to fail early, cause electrical issues, or just looked wrong. Part of that was my inexperience, but the bigger issue was cheap, low-quality LEDs.

When your alternator can barely keep up, though, you start rethinking things. That’s where LEDs began to make sense for me.

My MGB GT Experience

My 1969 MGB GT came stock with an alternator that put out just 35 amps — and only at highway speeds. For perspective, modern cars typically run alternators of 100 amps or more.

On a cold night, with the heater and headlights on, the car would nearly die at idle. Add the wipers and it was game over.

I started by swapping as many bulbs as I could for LEDs — eventually changing 18 of them. Some were inexpensive, shipped quickly from Amazon, while others were specialty bulbs from suppliers like SuperBrightLEDs.

Today, only a handful of incandescent bulbs remain:

• Alternator light (must stay incandescent for charging)
• Cigarette lighter trim light (no LED available)
• Hazard flasher dash light (rarely used)
• Reverse lights (rarely used)

Even before I upgraded the alternator and added headlight relays, the LED swap made the car far more drivable at night.

My Honda Acty Experience

My Honda Acty had a similar problem: the engine nearly died under load with the headlights on. Upgraded alternators are available, but they’re expensive. Instead, I turned to LEDs.

Swapping just the headlights solved most of the idle issue. But with eight bulbs at 1.5 amps each on a 60-amp alternator (if you’re lucky), there was more to do.

• Old bulbs: 18 watts/1.5 amps each
• New LEDs: 3.1 watts/.26 amps each
• Total load removed: 119 watts/10 amps

That’s a huge load removed from the system.

Inside, the stock dome lights were extremely dim. I upgraded to warm-white LEDs that mimic the factory look but are brighter, cooler, and more efficient. In the MG, I also swapped out the tiny 5-watt gauge bulbs for screw-in LEDs. For the first time, I could actually see the gauges at night.

Lessons Learned About LEDs

• You’ll need a new flasher relay.
  Most stock flashers are mechanical and depend on a large power draw to work. LEDs draw so little that you’ll get hyperflash (rapid blinking) or nothing at all. Look for an electronic flasher relay. They’re available for just about every vehicle, including Honda’s skinny style and Toyota’s oddball design.
• You get what you pay for.
  Cheap LEDs fail quickly. I’ve thrown away plenty that didn’t last as long as stock incandescents. Buy quality LEDs from reputable suppliers.
• Be careful with headlights.
  Headlights are safety-critical. Quality LEDs can be a big upgrade, but most budget ones aren’t good enough. In the Pacific Northwest’s rain, blue-tinted bulbs are almost useless, even if they look cool. In snow, they’re fantastic — but overall, aim for a balanced, white output.
• Pay attention to color temperature.
  Color temperature affects the look and usability of light. Higher numbers = whiter light. For interiors and license plate lights, I prefer warm white to keep a stock feel.
• Color matters.
  LEDs shine through lenses differently. A white LED behind an amber lens will look yellow, but a white LED behind a red lens will look pink. Use red LEDs for brake/tail lights and amber for turn signals.

Final Thoughts

Switching to LEDs turned two of my hardest-to-drive vehicles into much more enjoyable rigs. They’re brighter, draw less power, and run cooler.

If your alternator is struggling — or your dash is too dim to read at night — LEDs can be one of the simplest upgrades you make. Just choose carefully, buy quality, and match the right bulb to the right application.