New to Diesel. Have a 240D, 1977. Replaced glow plugs, fuse, battery, alternator. Did all this because glow plug light does not come on and when ignition switch is off a faint glow to the battery light is on. When I turn the key on the battery light goes off but the glow plug light does not come on. engine cranks. Forgive my sentences, I'm deaf, probably why they gave me car. Anyhelp, much appreicated.

 

Have you checked voltage at the glow plugs when they should be on? If not, the glow plug relay may be bad, or the fuse strip inside the glow pug relay. If the relay is working properly, maybe the indicator bulb in the dash is bad. Does the car start? Good luck.

John

 

Well it doesnt start, but I dont try to keep it turning over. The relay is under the steering column, I replaced it with one from the junk yard (MB charges 310.00. I did replace the strip fuse. The battery light on (faintly) with the key off puzzles me. Is it possible the ignition switch? I didnt check for voltage at GPs yet. Was a full day for me to find a used relay replace the glow plugs and altenator. This old body is very sore. Gezzer I am. Thank for your reply

 

I was also thinking it could be the Ignition Switch.

If you Engine has the Loop/Filiment type Glow Plugs there is 3 types of systems. Unfortunately I do not no at what year one ends and one begins.
However, one of the systems that has a Glow Plug Light you need to turn the Ignition key on as well as on US models pulling a small **** next to the Ignition Switch Back. The Switch with the **** is the Glow Plug switch.

On your type of Glow plugs system if 1 plug is no good or wired wrong none of them will work.
Also at the last plug at the front of the Engine there is a Ground Wire/Strap that either goes to a temperature sensor or is grounded to the Cylinder Head. If it is not there you system will not work.

 

Not one of those. Just turn switch on, glow plug light goes off, would start. Altenator went bad. Decided to replace plugs and fuse. Nephew replaced battery 2 years ago (was his fathers) and I made sure it was fully charged. Cant figure why light would be on with key off or not even in switch, unless its the switch. Dont know if its easy to replace or not.
Thanks again

 

I can see my Ignition Switch if I remove th lower panel below the dash board and above yout knees and if I more or less stand on my head and look up at the Steering Colum. I do not remember if you can see it by pulling out the Gauge Cluster or not. But, it looks very cramped up there.

When I looked at my favorite part seller they show 2 Ignition Switches; one that has 7 pins and one that has 8 pins. It said to take a look at your origional before odering.

I do not know if this will be helpful or not but on mine I pulled off the Alternator Wire Connector. The smallest slot on the Connector is the one the Blue Wire to the No Charging Light in the Instrument Cluster goes to.
With the Ignition Key in the off pisition there is no Voltage/Current there.
With the Ignition Key on there is Voltage/Current there.

The other 2 larger Slots connected to the Fat Red Wires always have Battery Voltage/Current.
And, my charging system is working OK.

 

Well being the old gezzer I am (64) I refused to try the simple thing of disconecting the new alternator, So after struggling with the new ignition switch for a couple of hours and getting the same problem (batt light on when key off), pulled the plug on the "new" alternator and tried to start, batt dead so jumped it and boom lit right off.. Never trust the part even if its new (or rebuilt). Now I have to go back to the dealer with the New alt and get another. But thats after new glow plugs, fuse, used relay and new ignition switch. Not to mention the sore back and and everything else that will happen in the morning. But I still love this old blue 240. Thanks for your replys Diesel 9112. You kept me looking.