I have a '91 W250 and have been experiencing electrical problems for some time now. One thing I have noticed is that the green wire coming from the voltage regulator has been melting the plastic inside the connector that attaches to the regulator. I have replaced the connector and voltage regulator and checked my grounds and it still seems to be doing it. What would cause this? Are there any likely suspects?

 

1st what the age & condition of your batteries ? also the connectors to batt. ?
None of that crud growing on them , load test the batteries , or 1st gen one battery .
I do not have a wiring diagram infront of me , but the reg should be sensing batt . voltage and putting pos. to the field one end and the other grounded , so I suspect the battery , then the alt. , the do it your self parts houses that I seen will do free testing , load test both the batt. & alt. , then just put in what you need .

 

The battery is only 4-6 months old (it only has one). The alternator could be suspect since I haven't changed it. It may be original to the truck. The battery cables look good although I've heard that there can be unseen damage lurking in the lead connector?

 

Get the testing I mentioned , any bad connections will heat up during testing , run your hand over cables & connections to feel warmth.