Janko,

Highky unlikely that more than one GP goes bad at a time. I've only see it happen once in 35 years of MB Diesel ownership.

How did U do the resistance test? Did U remove the connector from the GP to the GP relay?

When U have the old GP out, if they are parallel GP, test them across the battery to see if they glow. Hold each GP in a Vise Grip wrench and connect to the battery terminals. See if they glow.

P E H