I test backwards or from the ground at the end of the line, with the system installed and the ground freshly cleaned. You're looking for both opens and shorts (a dash element that glows too fast is an indication of a short). It's pretty easy to tighten the 'hangers' down too hard, crack the insulator and cause a short. A short can occur from coking (unburned fuel creates a path to the prechamber - good practice is to ream each time you remove a plug). Opens occur from blown loops and corrosion at electrical connectors, and results in the dash element not lighting or lighting slowly in the case of heavy corrosion. Checking backwards is easy and checks for shorts and opens at the same time: attach neg. lead of voltmeter to ground then feel your way up the line. The number will drop a bit as things heat up - the hotter a wire/element gets the lower it's resistance gets.

Also check the ground strap at the starter, battery connections, and starter connections. A little corrosion kills a lot of juice.

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daBenz - 1970 220D