Join Date: Jun 2005
Location: I would rather not say
Re: 166 Bulb warning light
A bulb is probably on the way out. I had a rear fog that turned milky and worked sometimes. However, it always triggered the bulb warning light!
If your bulb warning is coming on immediately, I would guess a sidelight, main, dip, number plate or brake bulb and not reverse, fog etc. I replaced all of the bulbs with units from powerbulbs.co.uk and still got the warning light. Two days later, a sidelight failed! I must have damaged it during install.
If it is easy for you to pick up bulbs, I'd just suggest waiting to see which one fails. None of them are particularly difficult to replace in the 166 (unless you have proper Xenons but these are highly unlikely to fail). Otherwise, you could order a range of bulbs (cost can add up!) or a bulb kit. Replacing the dips (assuming you don't have HIDs) with Philips Vision Plus 50% and setting the lights to the max allowable MOT level is well worthwhile.
I also have a rev counter bulb out but this does not trigger the bulb warning light. I'd have to check the manual, but I suspect the warning applies only to exterior lights.