Roast incoming…
Ever watched the voltage gauge on your 62 when you turn the blinker on? There a 0.5-0.75V dip. Not great, but not the end of the world. Now combine that with any other current consumption in the vehicle - HVAC blower, wipers, headlights, etc - and the voltage starts getting really low. Not only does that make each electrical device suffer, the HVAC blower might slow down for one example, but the engine rpms drop because the spark system isn’t able to pull the full current it wants to. If you dip below 12.6 system voltage, now you’re draining the battery.
Now, the reason for all of this - in my opinion - is because of two things. First the alternator isn’t able to supply a whole lot of current at idle. That’s fine, most aren’t. Mean Green or any of the “upgrade” alternators with a big number associated with them only supply that large amount of current when they’re spun up to high rpm. All alternators are pretty weak at idle. The second reason is that I feel the wiring gauges used in 60s are a bit undersized. This increases the resistance of the wire, causing a voltage drop, and less current delivered to each device. That’s where the larger charging cable comes into play with my fusible link replacement kit. Just upsizing the cable providing current from the alternator to the battery (and rest of the system) usually yields a 0.5-1V increase at idle. Upsizing ground cables, and cleaning the rest of the ground contact points, helps quite a bit too.
So what do LEDs have to do with any of this? They use far less current. They put less load on the system, freeing up available current supply for other things we can’t change, like the wipers or HVAC blower. It gives you more “headroom” so your spark system doesn’t suffer at idle and make the engine have lower rpm. Now, I will say I still run halogen headlights. A lot of LEDs don’t look “period correct”, which is a concern for some people (me) but not others. I’m fully LED except the headlights, but it took a long time to find ones that look appropriate for a 1982 vehicle.
That’s my long winded roast!
