Dipped headlights not working

[7_Malc]

Morning all… I had to abort my early morning blatt (K-series 140 Roadsport) when, after an hour or so of driving on full beam, I switched to dipped and… darkness… no headlights at dipped. Side lights (stupidly dim) work. Main beam works. All other lights (dash switches and dials, rears, numberplate etc.) are all working fine. No dipped headlights. Anyone else experienced anything similar and can point me in the direction of a fix? Thanks, Malc

[revilla]

Main beam and dipped beam are on separate 15A fuses. Main beam Fuse 8, dipped beam Fuse 9. Nothing else runs off Fuse 9 so if that went everything except dipped beam would work. I'd check the fuse first.

[Jonathan Kay]

(Crossed with Andrew's)

Have you got a multimeter and the appropriate wiring diagram?

Likely faults:

1. Fuse. Locate, remove, inspect. If it has blown it's worth putting another one in and seeing what happens even if you don't know the cause.
2. Switch. Work it a few times. Inspect. Then either see if the 12V feed is being switched to the dip beam output terminal, or check continuity through the switch, or swap the dip and main beam output connections and see what then works.
3. IGNORE: See #5 below. Relay. Locate, remove, inspect the terminals and the base. Probably easier to swap a good one in than check the old one.

Jonathan

PS: Great description of the fault. The details narrow it down a lot.

[SM25T]

If not the fuse ... trace the 12V to the main light switch and also to the dip/main switch. Could be a wire off.

[revilla]

@Jonathan - The relay is actually upstream of the Main/Dipped switch, so any failure of the relay would affect both. Surprisingly the switch handles the full current for the lights directly. The only things that are separate circuits for main and dipped are the Main/Dipped switch itself, wiring from there to the two fuses and from the fuses straight out to the lights.

[Jonathan Kay]

Thanks

Jonathan

[revilla]

Not sure how readable the following extract from the wiring diagram will be when posyted on here, but I've picked out the headlight circuits:

There's a Blue wire from Pin 87 of the lighting relay (and confusingly also a Blue on Pin 86!) which feeds the central terminal of the Main/Dipped switch. From the dipped side of the switch there's then a Blue/Red to Fuse 9 and then on to the lights. From the main side there's a Blue/White to Fuse 8 and then on to the lights.  

[7_Malc]

Problem identified - daylight helps - the toggle switch from main to dipped beam is failing (the bezel is falling apart). It will need replacing but tightening it up has remedied the issue for now. Hopefully I can source one that matches the 1999/2000 style.

[revilla]

Result!

[SM25T]

Try Chris at Redline 01883 346515

[Felixgogo]

Or better still, upgrade the plastic toggle switches with these quality metal APEM ones:

https://www.polevolt.co.uk/acatalog/Apem_Toggle_Switches.html

A straight swap, and all types available.

Cheers

Ian