Sometimes faulty plug also defects the relay.
Glow plug light 320 CDI W210 - Page 2 - Mercedes-Benz Owners' Forums
Glow plug light 320 CDI W210 - Page 2 - Mercedes-Benz Owners' Forums
panason1c
MB Enthusiast
When a faulty plug fails it can fail in one of 2 ways, open circuit or short circuit, if short circuit, it will cause one of the 'fusible' links inside the relay to 'blow'..........the relay is 'sealed' but can easily be prised open and the blown link(s) are obvious to the eye.
