Where's this 5V coming from?

spandit · Post by **spandit** » Sat Jan 29, 2011 5:06 pm

At the fusebox, on the fuses that protect the main beam headlights (5 & 6) I have zero volts as expected when lights are off. However, once lights are on (but not full beam) I get 5V across these fuses. When main beam is switched on, I get 24V as per normal.

Where is this 5V coming from then?

spandit · Post by **spandit** » Tue Feb 01, 2011 6:03 am

To answer my own question. After some help on a different forum, I traced the problem to bad earths at the headlights:

On Dip beam, Current would flow through the Dip filament but, due to the high ground resistance, would develop a few volts across it. this voltage would then appear in your fusebox via the unenergised Main beam filament. In other words the ground connection of one of your lamps may be a few volts above ground

Have cleaned all the earths which were dreadful! No more voltage problems for now!