Problem with Alternator Charging System

I have a problem and I think it is due to fried diodes in my alternator. Does anyone who knows how all of the pieces that make up the charging system work have any thoughts on the problem?

What happened is the battery in my Mk II would run down due to inactivity and I would use a low-amp trickle charger to recharge the battery. The battery is not a lead-acid. When the battery would not hold the specified charge, I contacted the vendor, who told me that I should not have used a trickle charger with this type of battery. However, they gave me instructions to try to see if I could reset the battery’s memory. Part of the procedure required that I pull the battery out and turn it upside down to see if any liquid comes out. It didn’t. Unfortunately, when I put the battery back in, I put it in backwards and hooked up the cables to the wrong posts – so I hooked up the positive cable to the negative positive and the negative cable to the positive post. I proceeded to recharge the battery and noticed that it did not seem right, which is when I realized I had the cables reversed. I disconnected the battery and reversed it in the car and hooked up the cables correctly. I proceeded with their charging procedure to reset the battery memory, but to no avail – battery would not hold the right charge, even when I kept it disconnected from the car. So I bought a new battery. I checked the voltage before hooking it up and it was fine. After removing the two fuses in the stock wiring system, I installed it in the car, connected the positive cable, and got an arc when I went to connect the negative cable to the battery and heard a click from under the hood. Investigating more, the click came from my voltage regulator. (See the attached diagram.) I first disconnected the brown wire that runs from the starter solenoid switch to the A terminal on the voltage regulator. That did not make the “click” sound from the voltage regulator stop when connecting the ground cable to the battery.

I disconnected the thick brown wire from the starter solenoid to the alternator BAT terminal and repeated the test. This time, no “click” was heard from the voltage regulator. I left that wire disconnected but reconnected the wire from the starter solenoid to the voltage regulator and touched the grounding cable to the negative post of the battery. Again, no “click” when I touched the ground cable to the battery post.

I suspect that the diodes are letting electricity flow in the wrong direction back to the voltage regulator when the alternator is not producing power. I think this might be a result of connecting the battery up backwards.

Is it possible the problem lies in some other piece of equipment, such as the voltage regulator or the starter solenoid switch? Any other thoughts?

Thanks!

Alternator

Check your ground strap under your car. Make sure not only the bolts are tight but it is tightly crimped in the ends of the braided cable. It may be crunchy like mine was and should not be. If so, replace. Also check for tightness from the starter lead to the solenoid. Mine was loose at both ends. Take a couple pics before you start so you can reflect on what it was like before you started.
Brian

Re: Alternator

Brian - Thanks for the suggestions. I will check them out tomorrow and report what I find.

Alternator

Hi David, if your nearby a business that rebuilds alternators/ starters etc, they can check your alternator out very quickly to see if it's putting out what it should, (alternator in or out of the car) probably even a garage can do this. You could also try a shop that sells just batteries and recycles them, they have a machine that hooks up to your battery (while in the car) and is able to test the charging system by what is coming back to the battery from the alternator/regulator.
I just went through this, this past summer. It was a head scratcher as there were multiple issues going on at the same time.
I'm interested to hear what you find.
Brian

Ground Strap and Starter Cable Connections Checked

I checked out the connections for the starter cable at the starter and at the starter solenoid, and both were tight and the cable was firmly attached to both connectors. The car's ground strap (under the car) was in good condition and also was firmly attached at both ends.

I am planning to take the alternator to a shop that did some restoration work on it and let them check it out. However, after reading the other suggestions, will also take my voltage regulator and let them check it out if the alternator is OK.

I am reluctant to hook up a battery until I know why the voltage regulator is operating before turning the ignition on. I am concerned that trying to run the engine might damage something even more. If the alternator and voltage regulator checks out OK, then will consider driving the car in for a complete, on-the-car check of the charging system.

Thanks for all the suggestions!

Alternator Was Checked Today

I finally was able to take my alternator to an auto electric shop so it could be checked. They hooked it up to their machine and confirmed that the diodes were shot. As I had suspected, having bad diodes allowed power to go backwards through the alternator and activate a relay in the voltage regulator when the ignition is off. I probably fried the diodes when I accidently hooked up my battery backwards. (I need to figure out how to mark the positive post better so the mistake never happens again! Maybe I might use those red and green felt battery pads.)

The shop said I should get my alternator back tomorrow. Will report if there were any other problems found.

Yep, It Was the Diodes

Picked up my alternator today. The guy who worked on it said that the problem was the diodes. He showed me some of the parts he replaced - in one look a person could tell that they were fried! Hopefully I can reinstall the alternator tomorrow afternoon and have the charging system working properly again.

Alternator

Hi David, it's good to know when you suspect a part being defective by someone who rebuilds them or really knows about it, and confirms that it wasn't right when you brought it in. Looking forward to hearing about how you released enthusiasm on the asphalt!
Brian