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Electrical Problems with my "87 Dodge Ram....Please Help!

I recently purchased an’87 Dodge Ram 350 3/4 ton Pick-up. It had 105,000 original miles on it and the body is in very good shape with a few small rust spots. The engine is in very good shape as is the clutch. I think I got a decent deal on it, I paid $750, and the mechanic I took it to to check it out said the body alone was worth the price.

I bought it from the owner and he threw in 4 used tires and rims.

After I drove it for a few days the engine died and I determined itb to be an electrical problem. My mechanic said the alternator was shot, so I replaced that and got a new battery as well. After driving it for a few days the same thing happened, the car died. I recharged the battery and it worked fine until the juice ran out. My mechanic then said the regulator needed replacing, so we did that and he only charged me $15 for the part, no labor costs. I drove it around and the same thing happened. I left it at the shop and they found one short and thought that would do it, but again, the engine dies after the battery is drained. The starter appears to be in good shape, when the battery is charged the engine starts right up even in extreme cold conditions. My mechanic has been very good about this and has not charged me anything since the first visit (except for the regulator), but we can’t seem to find the problem.

Somehow, the alternator is not recharging the battery when the engine is running. I say this because it only happens when I am driving, the battery does not seem to drain when I am not driving. The cables from the alternator to th battery are new as well.

Can anyone suggest a possible remedy that we have not been able to think of, or are we going to have to just keep looking for short until we find them? I had always heard that electrical problems can be very frustrating, and now I see why.

In themean time I am able to drive th truck for my everyday use with no problem, when the battery is fully charged, I can drive it around for a few days including some night driving with the headlights on. I have a small bayttery chargere that I connect at night for 3-4 hours and that seems to be a decent short term solution.

Please Help!!!

You need to check the voltage output of the alternator. Check it AT THE ALTERNATOR. If it isn’t at least 13.7 volts with the engine running the alternator / voltage regulator isn’t operating correctly. If the voltage is 13.7 or above check the voltage across the battery. It should be exactly the same as the output of the alternator. If it isn’t there’s a broken or burnt wire between the alternator and the battery.

I’m guessing that the fusible link between the alternator and the battery has failed. You’ll check that using the procedure above.

Sounds like a nice truck.

Going by what you stated it sounds like proper troubleshooting procedures are not being used to locate the trouble. Since you have replaced the main components in the charging system and haven’t got good results from that then a problem in the wiring between the areas may be the cause of the trouble. It is pretty simple to see if the charging system is working correctly and check for parasitic current drains on the battery while the vehicle is parked. If your mechanic can’t do these tests and doesn’t have the proper test equipment you may want to take it to a shop that can better handle the trouble.

Here is the wiring diagram for your p/u: Click on Fig. 13. It shows that there are two black wires on the alternator. One of the black wires goes to ground. The other is “hot”. It should have battery voltage. If it doesn’t there is a fusible link that has probably burned.
What can you do? You can use a voltmeter (multimeter) to check for power on the wires. Because there are two black wires, check to see if one goes to ground. Then, the 12+ volt wire is the other one.

Only Chrysler would make a black wire “hot” and the one next to it “ground”…Does Chrysler still use an external regulator? These trucks haven’t changed since 1972. And even in '72, they didn’t change much…