Good suggestion.

I checked the glow plug relay. It operates as expected and the relay seems fine. The relay has a constant 12-V (big wire) supply and all six contacts that go to the six glow plugs get 12-volts anytime the relay is engaged. The relay must be engaged from voltage supplied by a smaller wire.

The problem is that I don't always get the voltage (small wire) required to engage the relay. I need to determine why I sometimes don't get this voltage when I turn the key.

Could this be only a problem at the ignition switch or could it be something else (the computer or something)?

__________________
Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)