RHS Dip Beam Problem

[Stagless Steve]

I've got a weird situation with my right hand side dip beam not working. The bulb is fine, but I bought a new one anyway, but that didn't work either. Main beam works fine. When I connect the multimeter to the black and blue/red terminals of the headlight plug socket it shows just over 11v with the headlights on (see photo). So, the tests show that the bulb is fine and power is getting to the dip beam terminal, but when I fit the bulb to the socket, the dip beam does not work.
Any thoughts on what might be causing this would be gratefully received.

[mole42]

There is a bullet connector between the bulb connector and the front harness, chances are that has become disconnected. It's a bit of a bear to find, I usually end up taking the centre grille out so I can see inside with a bright flashlight and fish around until I grab the wiring.

[Stagless Steve]

There is a bullet connector between the bulb connector and the front harness, chances are that has become disconnected. It's a bit of a bear to find, I usually end up taking the centre grille out so I can see inside with a bright flashlight and fish around until I grab the wiring.

Thanks mole42. Would I still be getting a voltage on the multimeter if that bullet connector was disconnected?

[mole42]

No, but 11V (would expect over 12v from a healthy battery) suggests it's slightly corroded or loose so you might see a voltage when the bulb is not connected but it disappears when there's a load. 50-year-old car electrics are fraught with issues to do with slight corrosion or slightly loose connectors or slightly high resistance in a circuit. It could also be a slightly loose fuseholder at the bulkhead.

[Peter707R]

I fitted relays to control both main and dip beams with direct (fused) feeds from the battery so the existing wiring harness only needs to pass low currents to operate the relays. Will improve brightness on its own but then have Osram Nightbreakers for extra!

[Stagless Steve]

Thanks everyone for your excellent advice. It was indeed dirty bullet connectors. All is now working.

[richardthestag]

Thanks everyone for your excellent advice. It was indeed dirty bullet connectors. All is now working.

great news, more oft than not a bad terminal on the feed or the earth will create high resistance, which then creates heat, which then further corrodes the terminal etc.

You may well see battery voltage when there is no load but as soon as you connect the bulb the voltage will drop off quite fast.

Blame Georg Ohm for finding this out and documenting it as part of Ohms Law and annoying every single bored O-Level Physics student. Mind you Newton discovered gravity, just think had it not been for him we would all have flying cars by now

[Stagless Steve]

great news, more oft than not a bad terminal on the feed or the earth will create high resistance, which then creates heat, which then further corrodes the terminal etc.

You may well see battery voltage when there is no load but as soon as you connect the bulb the voltage will drop off quite fast.

Blame Georg Ohm for finding this out and documenting it as part of Ohms Law and annoying every single bored O-Level Physics student. Mind you Newton discovered gravity, just think had it not been for him we would all have flying cars by now