I'm a 124 diesel guy, but I'm currently doing some restorative work on a '62 190D, and was hoping to upgrade the glow circuit. Has anyone with the older OM621 or OM615 engines upgraded to the 18mm pencil tip plugs and then added a regular OM616 relay? I have a used relay from an '82 240D, and was hoping to just wire it into the ignition switch, with a small LED indicator in the dash. Seems like this should be fairly straight forward, even though the temp sender would be deleted, not unlike the violet wire mod for afterglow. I just checked the resistance values of the pencil tips, and they're the same as those from an OM603, so this all seems rather doable. The starter and fuel shutoff will still be handled by the gorilla knob.

Anyone out there with direct experience going this route? Thanks