Hi,
passenger dip beam has been intermittent for a while, sometimes it works, sometimes it don`t! I have the changed the bulb and the ballast unit now, and it is still intermittent. Any ideas gratefully received!

I would be looking at earths to body and connectors to the headlamp harness. BMW i3 Electric Car
2012 Full Fat RR 4.4 TDV8 (now gone)
2006 VW Touareg 3.0 TDi V6

The dip function is performed by a shutter coming down over part of the beam to blank out that section thereby "dipping" the headlight.
Hence the reason why changing the bulb and ballast has not cured your problem.
The chances are the shutter is not operating consistently.
As above have a look at the connections first but if no luck you really need to take the headlight unit off the car and take it to bits. It could be that simply spraying a silicon spray on the shutter mechanism might free it.

But if the shutter was sticking surely the OP would be complaining that the HID main beam is not turning off?

I assumed it meant the HID bulb was not turning on reliably? David

Please let me know if my comments upset you, I may wish to upset you again.

check the wiring that goes to the headlight - on mine the wiring to the big headlight connector had chafed through where it was rubbing against the metal structure of the car body. Took me a while to sort it out. 2006 MY FFRR 4.2 S/C autobiography (Auckland Blue - 901)
1996 Discovery 300Tdi S (death by rusting) (Silver)
1995 Volvo 850 T-5 est (now in Valhalla) (verdigris metallic)
1987 Volvo 240 GL est (now in Valhalla - not owned but driven lots)
1990 Kawasaki ZZR600 Blue
1979 Honda CB250 NA Superdream Red