Happy day after Thanksgiving all!

1975 240D - To start this car you need to have the key turned to the "on" position and pull out a knob that allows you to see an actual glowing element. When it is nice and bright red give it a pull and ta-da the engine starts...well for the last 29 years anyway. I've been told that is called a "pre glowplug starter". Is this the case because I am having a heck of a time finding one at my usual haunts online. This is my father-in-law's car and I'm trying to give him a hand as I have a '80 300TD and that is the dash light glow plug indicator. His car only starts some of the time and he doesn't want to get stranded so, thought I'd give "the shop" a stab at it before I start calling around town. His mechanic said he adjusted this part and now it should work better, but it is really not completely fixed.

Any help would be appreciated.

Todd