Depending upon the start cycle, the c223T will supply a lot of current if it is a cold engine for a few milliseconds, not long enough to burn anything out. a warmer engine upon restart, will have the lesser amperage applied to the glow plugs. (via the 2 relays combination) There is a special analog discrete circuit "computer" in the drivers kick panel, and two relays on the inside passenger side fender behind the filter assy. ON the glow plugs is a common strap with an additional strap which is a thermistor and this is what supplies the current resistance over time delay to the glow plugs.

It is really a cool and complex design. I prefer my 2001 CTD dodge ram blow dryer though to glow plugs!