Wires in 300SDL Fuse Box

[Marvin Smith]

I recently bought a 300SDL and have been trying to find out why my glow plug won't light when I first turn the car "ON". I decided to check the fuses in the fuse box and found a loose red wire as well as what appears to have been where a wire has been cut or broke. The problem is that in my manual it does not show a wiring diagram and what should be in the fuse box. There is one bit of information that might help - there are two terminals with spade lugs attached to them in the fuse box that are separate from all the other fuses in the box. The place where the wire was cut or broke is on one of these spade lug type terminals. what do you think?

[Benzmac]

Most of the time, these are from an aftermarket phone or alarm install.

I would check the glow plugs/ There is a glow plug relay on the driver's fender, it has the wires for the lamp.

[Marvin Smith]

Mr. Drummonds:

[Marvin Smith]

Mr. Drummond:

Thanks for your prompt response. There are two inquiries which i sent for help. The first one dealt with the inability to get the glow plug lamp to light when the car is being started. I reviewed this with the mechanic who installed a new glow plug relay with the expectations of solving the problem. The car is still hard to start and the light does not come on even though the mechanic applied voltage to the wire connected to the light and it lit as it was supposed to do - the light is good. I am looking at the scenario where it appears as if the resistivity of the glow plugs has increased significantly due to extended use and time. The mechanic measured the voltage on each glow plug during starting and all plugs had voltage on them - he still recommended that I install new glow plugs.

I checked the resistance of the plugs today in lieu of measuring the glow plug current on Monday to ascertain that the glow plugs are indeed bad - i think maybe two of them are bad after measuring the resistance. Four resistances were about one ohm each, while the other two were all over the place. Even though there was voltage on all the glow plugs, somehow the glow plug relay is sdtill not providing voltage to the glow plug lamp and starting is very difficult - maybe a broken Wire?.

Is there a thermal relay as well as the glow plug relay? If so, where would it be? I intend to go to the Mercedes dealer on Monday to look at electrical diagrams in order to solve this problem. Your advise please.

thank you,

Marvin Smith