Does anyone knoe what the voltage should be at the headlights ("dipped beam") when the engine is running?
My '45 has had something wierd going on for a year or two.. but it's only an issue during the dark months, so I've sort of lived with it up until now.
I'm finding that headlamp bulbs only last about 3-4 weeks. The off-side one seems to be the more vulnerable... the near-side one lasts about 6 weeks... but they both die fairly regularly.
Only the headlamp bulbs are affected. The side-light bulbs, rear lights and instrument bulbs (which do the same "hours") don't die.... (e.g. the instrument bulbs were new in 2010 .. number plate in 2012.. with no problems since).
So what's going on?
Since it was just the headlamp bulbs affected, I thought it might be a vibration/rattling around thing (or defective bulbs etc.) so it took a while to work out what was happening and spot the pattern that was emerging.
I tried different brands of bulbs... but they all died fairly quickly. I then tried fitting "Heavy Duty" bulbs instead... since they claim to be more resistant to vibration. They lasted longer.. but still just 6-8 weeks, depending which side they're in.
While I was mooching aboot in Halfords (buying more bulbs!) I saw some "Long Life" bulbs which claim to give better durability to "over-voltage".. I've stuck some in there and we'll see how it goes....
But it got me wondering if voltage was an issue... While the bulb was out I measured the volts at the bulb connectors. The beast has 12.x volts with the engine off... but it increased to 14.x volts when the engine was running.
I also noticed that the wiring on the off-side looked brittle and partially "cooked" so it obviously runs a bit hotter than it should. It's not shorting out at all... but I now reckon it's a bona-fide electrical problem..
Any ideas if my voltages are correct? And if not, what controls the volts to the headlamps..? (wondering why all the other bulbs aren't similarly affected)?
Luckily the bulbs is a 2-minute job on the '45... rather than a bumper-off job... but I'd like to sort it (bulbs being a bit dear, when you're buying a dozen each winter...