I have a weird issue with a 83 300SD. I believe others have had this happen but I have not seen a solution.

Replaced all glow plugs (new Bosch) as well as the new upgraded glow plug relay.

When you put the ignition to the glow position the light does NOT light, count to 5 or so and it starts no issue, in recent cold weather (-10C) I have has no issue starting the car by waiting about 25 seconds - and no need to floor the gas etc as the manual indicates may be necessary - so the glow plugs are functioning well. In addition I can notice the lights get brighter when driving after the extended glow cycle completes.

The real weirdness is that if you turn the ignition on wait 5 or 10 sec and then cycle the ignition again now you do get the glow light to light- full bright and it goes out after a relatively normal light cycle?

So the bulb obviously works and the plugs work, why would the dash light light come on only after a second switch cycle?

I'm just living with it for now as everything seems to be functioning - cold start etc.

Paul