Hi all,

I want to start by saying that I am new to the forum here, and that it is unbelievable how much I have learned from reading through hundreds of posts, so thank you to all of you for sharing your knowledge.

On to the problem... I have a 1990 W250 that I am in the process of turning into my primary vehicle. When I bought the truck, the owner mentioned that it was having charging issues, and that he had cut the green wire running from the alternator to the voltage regulator, and spliced in a ground wire himself. I have since removed his so - called ground wire, and have re-connected the green wire where it was cut, installed a new voltage regulator, and added a ground wire from the voltage regulator to the negative battery terminal. The truck's voltage would fluctuate when first started, but was holding steady around 14 volts when up to operating temperature. When I got in the truck today, the factory voltage gauge never moved, indicating no charge. It worked perfectly fine last night, showing a perfect charge while I was driving around town.

Is this a gauge problem, or is my alternator shot? Thanks in advance!

Jake

 

There are smarter people than me on this website but the first thing I would do is get an accurate digital volt meter and check voltage at the battery terminals with the engine running...also know that there are many voltage regulators that are either defective when new or become so shortly after installation. It seems like the quality is very poor. The voltage fluctuation you see at startup should be grid heaters cycling and it is normal. Also the factory voltage gauges are notoriously inaccurate but will usually register something. Do you have an aftermarket voltage gauge or did you get your 14vdc reading from a tester?

 

Check the voltage at the 2 field terminals on the alternator with the engine running and it's not charging.

If both are at battery, the VR or wiring is bad.
If both are at ground, supply to the VR system is bad.
If one is at battery, and one is at ground, the alternator is bad.

hope it helps

 

I guessed it to be running about 14 volts based on the factory gauge - but that is only a guess. It just seems odd to me that the gauge in the cab wouldn't register anything...

 

I've got an overcharging problem now that I've installed VR .., get a decent multimeter and follow EVERYTHING jmartin tells you to ... He helped me work through my problem and I'm sure a new VR installed on Monday evening will fix my problem .

I'm new and I'm learning... So far DTR and the folks I've met here have been hands down the best help I have had.