Glow plug issue
 

I've been having a weird issue with the glow plug system on my 300SD. When I turn the key to the glow position, the bulb does not come on, however the glow plugs do come on as the car starts fine in cold weather. I've been turning the key and waiting about 10 seconds before starting the car in cold weather.

I can get the glow plug light to come on, but I have to turn the key 2-3 times.

Why would my glow plug light not come on originally, but come on after 2-3 cycles of the key? I'm not sure if there is an issue with the relay as the glow plugs have been working okay.

To be safe check the Glow Plugs with an Ohm Meter. Not a endosement to by Parts there but Diesel Giant has a good pictorial on what to do under Diesel Glow Plug Repair at his site.

Take a look at the Strip Fuse on the Relay to see if it is cracked or the Screws that hold it down are loose.

Connections in the ignition switch?

Maybe, but the glow plugs do work, the light is just intermittent.

Yeah, but perhaps something in the ignition switch is interfering with the dash glow plug light, as you mention you can turn the key a few times and it works.