Yet another electrical puzzle.

Hey all, another moment where after money spent on a local mechanic who was also left scratching his head, I'm stuck.

Highbeam does nothing, I've replaced the entire steering switch unit but no dice. The mechanic checked everything they could think off, usual fuses, Earth etc.

Got any ideas on anything else


defender 90, 1996, 300tdi.

This should be a very simple fault find. Break down the highbeam cct into its constituent sections...

1. Fuse
2. Wire i/p to light switch
3. Wire o/p to relay
4. High beam relay
5. Wire to H4 bulb
6. Earth

#1 check each of the above for 12v when switch on
#2 check for guaranteed zero ohm ground/s
#3 check for any high resistance and/or partial shorts with adjacent lighting ccts
#4 check for 100% continuity/zero ohm resistance between headlight link wires for both main beam and high beam

If your 300tdi has the voltage regulator this can throw some wobbly faults :. check voltage regulator

+ are you getting the full beam dash light 'ON' with high beam?

assuming its has dim/dip the first thing to check is that all the tab connectors on the fuse box and lighting relay are in place and have not been pushed backwards out of their holders