Battery light on

Hi guys. Excuse me for butting in here but the warning light is simply telling you there's a problem. It's doing what it's supposed to do. The most common failure, especially when it's intermittent like this, is worn brushes. Unfortunately, after 35 years of one of the easiest charging systems to diagnose, the engineers at Chrysler found a solution where there was no problem and they changed the wiring of the field circuit. You can't use voltage readings anymore to diagnose worn brushes.

My reason for sticking my nose in here is I know Zemorzemor works on more vehicles than the average car owner, and I'm hoping to learn something about this system. Unlike the older systems, this one has one field terminal grounded instead of being supplied with full battery voltage. The other one is supplied a varying voltage from the Engine Computer. It is varied from 4 to 11 volts depending on the needs of the electrical system. A higher voltage makes a stronger magnetic field, and produces more output current. What I'd like to learn is what happens to that voltage when the brushes are open. It's either going to stay at the control voltage of around 4 - 11 volts or it's going to go up to battery voltage. If it goes to battery voltage, that will be a dandy clue to diagnosing these systems.

You may have to resort to measuring for continuity between the two field terminals with an ohm meter, but even that presents problems. If you find around 4 ohms, the brushes are making good continuity right now, but that doesn't mean they will after the engine has been running a while. If they measure open circuit, they could be worn or there could just be a chip of carbon holding them open. Even with a good or brand new alternator, the brushes will read open over half of the time until you irritate the pulley a little.

First look in your area for a starter / generator rebuilder. All larger cities have them. The guys at any auto parts store will know if there's one near you. I just put a brush assembly in one of my Grand Caravans last summer. The part cost nine bucks.

We also have a farm supply / hardware store chain that has starter and generator rebuild kits. I just checked my favorite online source and the brushes weren't listed. I think an '06 might be too new. From the picture of the alternator for your car, it looks like a Nippensenso unit. They have a stamped steel cover to remove, then three small bolts hold the brush assembly on.

You can also do a search online for "alternator parts". There's a lot of places that sell them. I sell all kinds of brushes and starter repair parts, along with selling and repairing Chrysler car radios, at the nation's second largest old car show swap meet about 50 miles from my home.

The reason these parts aren't available at auto parts stores is most do-it-yourselfers wouldn't know how to diagnose or perform this repair, and professionals don't repair customers' cars this way. It takes extra time and there's the chance of doing something wrong. Customers usually get more angry at having to come back a second time than they do if you sell them a complete rebuilt generator at a much higher cost. Labor cost is less; parts cost is higher, so it evens out, and the chance of something going wrong is much less. Also, a rebuilt alternator comes with a warranty. For those two reasons, brush assemblies aren't real popular so the auto parts stores don't stock them.

You can also try ordering the assembly from the dealer. I doubt they will have it in stock for the same reasons I just mentioned. Years ago I often bought replacement brushes with the insulating holders and washers for the '70s and '80s Chrysler alternators, from the dealer for around five bucks for the whole kit that included more parts than were needed. Today you can buy just the pair of those brushes, without the extras, for about three bucks from those rebuilder companies.

I have a web site too geared toward students, instructors, and do-it-yourselfers with a page about this alternator and how to replace the brush assembly. We aren't supposed to post external links here but if you are able to send me a private message, I can give you the name of the web site if you think it will help.

I saw your question for this problem and posted this reply:

The engine rocks when you shift direction or accelerate. Look for anything that moves at that time. There's a lot of different kinds of noises, from metallic clanks to creaks and thumps. Also look at any flexible joints in the exhaust system. Check the rubber isolators in all of the engine mounts to see if one is deteriorated and hitting metal-on-metal.

Other than that, my best suggestion is to have the car in the air on a drive-on hoist so you can watch what happens when a helper shifts it.