We have a glow plug controller manufactured for the Mercedes conversions that is adjustable from 1 - 120 seconds that works automatically when the key is switched on that will work on your 110, if you run out of options.
The ballast resistor drops the current for the early 90 & 110 and the series vehicles.
If you switch to the later glow plugs, you won't need it.
Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)