Idiot Lights Don't Work - then they do

[Ralph Burnette]

I have a 1993 300SD (w140) with about 212, 000 miles on it.

Lately, when I go to start the car, I turn the key for the glow plugs to heat up per standard practice. However, only the SRS
light comes on. A couple of seconds later, the rest MAY come on.
If I turn the key off then on again, the idiot lights come on and
the car will start.

Usually, this will happen at the first start of the day, but
sometimes other times, too.

After letting the car sit for a day or two, I check the voltage
of the battery at the poles. 12.38 volts. The water was a
little low in one or two cells but the plates were covered.
The battery is about 2.5 years old.

Prior to the above symptom, I would notice sometimes
when I got in the car, that the interior lights were a little dim
then would get brighter.

I would appreciate any help on diagnosing this problem.

Thanks!

[mr. Goodwrench]

You may need a new ignition switch. These cars have the faulty wiring harnesses with poor insulation. I have the same car with only 64,000 miles on it. We have not had any problems like yours YET. My wires have insulation that is cracked and split! It also sounds like you have a bad ground connection somewhere in the system.You may also need a new dome light switch. Does the dome light problem exist regardless which door is opened? If so, the problem may be confined to the dome lite electronics. Were any of the above items replaced in the past?