Hi, when I drive with a low beam, the high beam lamp on the dashboard glows (slightly, it is discernible only at night).
Where should I start tracking the fault?
Current theory is bad earth, possibly the common one under the battery as LH headlamp seems yellowish (change of the bulb did not help).
Thanx.

Yes, check headlight bulb connector plug. They often overheat and crack, causing a loose connection, which gets hot also. Also tighten the spade terminals themselves, by squeezing carefully with pliers.

I found that a headlight plug off a much older FIAT 128 could accept the terminals from the newer models, and make a good contact.

I think you're definitely on the right track, it's most likely to be an earthing problem which causes the low beam to earth back through the high beam circuit.

-Alex

Case closed .
It was the bulb bad earth. After some experimentation involving contact cleaner sprays, sandpaper and the tip of the screwdriver, I ended up with a "new" bulb socket and some soldering.

Good stuff.

Given that this is the easiest 'end' of the system to start from, I'm relieved that's all it was.

Next project for you: relays and 10-gauge cable from starter motor terminal

-Alex