Reviving a thread to add my own experiences. Car (87 300D) getting hard to start when cold. Pulled the relay cover. Measured 12.5VDC at each pin. Measured resistance:
G1- 140K ohms
G2- 51.1 ohms
G3- 1.0 ohms
G4- 4.86K ohms
G5- 1.0 ohms
G6- 18.5 ohms
It would appear that only two GPs MIGHT be good.
Glow plug light on the dash lights up...sometimes...often every OTHER turn of the key. When it does light, is stays on approximately 5 seconds. I'm starting to believe the light means nothing other than the key is in the correct position and the bulb is good.
-Louis