Glow Plug indicator light: 06/85 300SD

My problem stems from a glow plug indicator light or glow plug circuit that is malfunctioning. When I turn the key to the "2" position the light will not come on, even though the interior light goes dim. After cycling the ignition switch engaging the starter 4 or 5 times the light comes on and seems to work properly, the colder it is outside the longer it stays on. The car is not particularly difficult to start when it is plugged in, what concerns me is leaving the vehicle for longer periods of time where it can not be plugged in. Almost forgot!! 06/85 300SD. Thank-You in advance for replies, Merry Christmas to all, and to all a good night!

To see if the glow plugs are actually working, simply measure the voltage at the glow plugs individually. They should be around 10 to 12 volts as soon as the ignition switch is put in the on position. If you're not getting this voltage, start by checking the bar fuse inside the glow plug relay on the passenger side of the engine compartment.

Good luck,

[be459]

I think the fuse is still good since the interior light goes dim. It sounds like one of your glow plugs is out of specification. Change them all, you should fix the problem. If you really want to test the plugs before changing them, you need to measure the DC current of each plug. I do not remember how many amps for each plug. Search the forum, you should find the answer.

David

My experience with pin type glow plugs has been that electrically testing them can only determine a bad plug if it has been burned open. There are other things that can be bad about the plug that won't show up with an ohmmeter or current test. The shells burn, the nichrome wire inside maybe shorts against the shell, or maybe they corrode internally preventing them from efficiently transferring heat.

If you have voltage at all the glow plugs, it is worth replacing all of them. Most of the time in my experience, this will put a pin type glow plug engine back in the easy start category.

Good luck,