Thread: New Era twin headlight relays - are they still good today?

Originally Posted by TonyC

Is there any reason why you wouldn't pick up power from the starter motor, the alternator or the under bonnet fuse box, which has a couple of unused slots, and is supplied from the starter motor as far as I can tell.

Tony

None of the vehicle manufacturers take power for the lights, or anything else, from that location, why I do not know.
During a run of one of VWs Golf’s models, they for a short time powered the lights from the alternator, as it meant a shorter wire run.
But half way through the run, for some reason, they went back to powering the lights from the cranking battery.
While I have no idea what the problem was, I prefer to play it safe and come off the cranking battery.

Would the voltage from the battery be more stable than from the alternator?

Originally Posted by V8Ian

Would the voltage from the battery be more stable than from the alternator?

Not by much, but there is a massive amount of voltage spikes at an alternator, where as the battery acts as a huge voltage suppressor and this may be why there may have been a problem when VW did it.