1997 Dodge Grand Caravan Battery/Alternator issues

A used alternator is not a good idea in this case because the single most common problem is worn brushes. They can be replaced separately if you can find the assembly. I buy them from a local rebuilder for less than 20 bucks.

Start by measuring battery voltage with an inexpensive digital voltmeter while the engine is running. It must be between 13.75 and 14.75 volts. If it is closer to 12.0 to 12.6 volts the alternator is not working. Measure the voltages on the two small wires or terminal nuts on the back of the alternator. These must be measured with the engine running. You will find 0 volts on both of them with the engine not running. One of those terminals must have full battery voltage. The other one must have less but not 0 volts. If you find the same voltage on both wires, either the voltage regulator in the Engine Computer is defective, (pretty rare), or the dark green wire going to it has a break, typically at a connector. If you find 0 volts on the second terminal, the brushes are open. They can be replaced separately. On some models you can do that without removing the alternator from the engine.

The voltage testing must be done when the battery light is on because that's when the problem is occurring.

Actually, if it is the brushes, that is the most common but the least expensive problem. If you have a pick-your-own-parts salvage yard nearby you can find some of these alternators mounted in some cars in such a way that you can pop the rear cover off and remove the brush assembly without even removing the alternator from the engine. If you're anywhere between Indianapolis, Ohio, and southern Georgia or Alabama, I can recommend a real clean and well-organized chain of yards where the parts are real inexpensive and the people are very friendly.

I "busted" a lot of these to create real-world "bugs" for my students to troubleshoot. Here's three photos from one of those minivans. The first one shows the four nuts that must be removed after the wires are removed. Next the cover can be prided off. It might need a little tapping but it won't come off very hard. The second one shows what you'll see with the cover removed. In the third one, the old, worn brushes are on top and the new assembly is on the bottom. You can see how much longer they stick out in the middle. The old assembly is still bolted to the terminal block. You don't have to take that out. It shows the screw removed from the left side. Besides that one, all you have to remove are the two on the right side. Push the spring-loaded brushes down with your finger to slide the assembly on.

I don't know if you ran into a problem last time but if you promise to be careful, do not disconnect the battery cables. You might have a large bolt-in fuse in the under-hood fuse box that is just for the alternator. You're better off removing that to prevent sparks. That is because I remember very well the frustration of reprogramming the heater / AC controller after the battery was reconnected. I can post the calibration procedure but the AC system must be working properly for it to work, and even then you might have to run the test more than 20 times before it works. If the six yellow leds in the push buttons aren't blinking now, it's best to leave the battery connected so that computer's memory isn't lost.

Yup. Based on the following: Worn brushes are an extremely common problem in the Nippensenso alternators. A used one is likely to develop the same problem. With the used one, you didn't have a problem for almost three months. And the clincher, you found 10 volts at the battery while the engine is running.

There are basically four things that can cause that 10 volts while running. Worn brushes, defective voltage regulator inside the Engine Computer, a break in the wire between the alternator and the voltage regulator, and a break in the feed wire to the alternator. To narrow it down and verify the brushes are worn, measure the voltages on the two small wires on the back of the alternator as I mentioned earlier.

The brushes will be responsible for 98 percent of the problems. If you still have your old alternator, you can use that to practice disassembling it to see what's involved. Every year I had my students take a few different models apart to peek inside and see how they work. This one is much easier to do than to describe. My kids needed lots of instructions and hints with GM and Ford units, but with the Nippendensos I could just stand back and let them go.

If you aren't afraid of a screwdriver, I'm confident you can replace the brush assembly. If you can find a used alternator to practice on, I think you will find out that YOU will have the confidence too.

And you're not wasting my time. If I wanted to help only professionals I wouldn't be here on this site.

Nope; you're right. What you MIGHT have overheard has to do with the GM generator. They went from the world's second best design, after the Chrysler alternator, to by far the worst pile ever starting in 1987 models. Because of their design, they develop huge voltage spikes that interfere with sensor signals and can destroy the generator's internal components. It is real common to go through four to six of them in the life of the vehicle. What many professionals are finding out is the number of repeat failures can be reduced by replacing the perfectly good battery at the same time. As batteries age, they lose their ability to dampen and absorb those spikes. The old batteries will work fine in pre-1987 cars. To the best of my knowledge, that does not apply to Chryslers or any other brands of cars.

The worn brushes I told you about are a real common problem, and there is nothing else you have to do or worry about when you replace them. The biggest "worry" is whether the two tiny terminal bolts will snap off if the nuts are rusted tight, but newer models use a plug-in connector, and even if yours does have nuts, you had them off a few months ago. Those studs can be replaced with regular bolts if they break or you can rob the part from a cadaver alternator.