I posted about this yesterday, didn't get much help and did some more testing last night.

Basically the problem is when I turn the key to "On" initially I notice a substantial voltage drop (battery goes from 12.4 to 11.4), turn the key off and back on again and the voltage does not drop as low (high 11s). The drop is substantial enough on the first key turn that it seems to cause the GP relay to NOT give power to the glow plugs, hence no glow plug light.

Tested battery at Autozone and Napa Auto, both said it was fine, as was the alternator.

Tested the relay for power, tested that all the GPs are getting power (they are brand new), tested the GP harness for continuity. I really don't know what to do and am looking for somebody who understands the 603 GP system and can point me in the right direction.

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-justin

1987 300TD, 1987 300TD
2008 R32, 2000 Passat Wagon