Hi all, I have an 1988 110 with the same type of problem? my hand brake light on the dash glows dim all the time and I can't find a switch anywhere near the hand brake, I have top up the brake fluid but the light is still on, it always work ok, until I change the engine from a 2.5 n/a to the tdi 200, just wonder if I have left a wire off or it not going to ground some where, but as I said I can't find the switch? I'm sure one of you chaps here will no where this is any help would be appreciated thanks MBF

sounds to me like the dash is earthing through the hand brake light bulb.

The switch (if you have one) will be on the handbrake lever under the rubber boot.
Our 86 90 did not have aswitch so the light did nothing till we fitted a 2nd hand lever.