Mercedes Benz repair: 1978 mercedez 240d diesel 4 speed ..., temp gauge, glow plug

Question
hi, my 1978 mercedez is giving me problems, the orange coil light wont turn on to heat up the coil and it makes the car hard to start. Please guys i need your help i check the light bulb and the fuses and they're okay. thank you

Answer
Good morning Randy!
This would be a glow plug problem.
You will need to remove the glow plugs and test them. You can do this with a multi-meter.The bad one maybe visible after you remove them. Check the resistance on each one. The one that is giving you the problem will make your needle shoot way up when testing. Touch the hot(red)to the prong where you hook up the electrical eye, Then ground(Black)to the body of the glow plug(near the bottom). Compare all 4 and pick which one is acting up. I dought that all of them are bad, although i have seen them like this. There is also a relay depending on the year of your car. This should click after 15 seconds or less after cutting on ignition switch.If no problem found there, Check your switch on the head. There is two of them there. One is for your temp gauge and you can find out which one that goes to by unplugging and checking your temp gauge.The other goes to your glow plug system. If you have any trouble feel free to ask. I hope this helps! Thanks and good luck! Ricky