Richard,

In addition to a pre-glow relay fault causing the current drain, other common causes are the radio automatic antenna (if your car has one) or an interior light door-switch fault. I've even heard of the light in the glove box faulting on and causing similar ills.

I like the idea of the extra light on the glow-plugs so you have a nice visual indication that the glow plugs are energized when they should not be. I have an old turn-signal bulb socket with bulb that I use for a test light, attach a couple of wires to the contacts on the base and alligator clips on a few feet of wire, use some electrical tape to prevent a short and put the bulb out the hood at the base of the windshield. If you see it light while the car is not running, or light up after you've started the engine, then you know the relay is the source of your drain.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC