Yes, once again Ken comes through for another member of this forum, folks!

Ken, your advice on my alternator did the trick! I changed out the Diode trio as you suggested to get rid of the charge light staying on on my console, and it worked! $6.00 at the local auto parts store. About a total of 1 hour to disassemble, run to the store, pick up the part and put the whole thing back together and mount it back in the car. Hardest part was trying to get the brushes infront of the springs, just because it's cramped quarters. The whole trick of holding in the brushes and springs with a toothpick was great and worked like a charm.

I'll never cease to be amazed by the knowledge that Ken has offered to all of us here at C3VR, and am extremely pleased that he chose to bless us with that knowledge.

Now, if we can all just step back and let Ken get some work done on his own ride, I'm sure we'll all be grateful as he shares his progress with us.

I truly look forward to the day I can meet Ken face to face and shake his hand and offer my thanks in person.

I'm thinking Ken deserves a BIG OL' BRICK at the NCM

Heck, put me down for $100. Anybody else?

John

Thanks guys. The brick should be for all of us. C3VR. I don't deserve one for myself. I enjoy helping.

Hi
I have the same problem with the generator light staying on but very faint. Is there a part number for the diode trio? Called one parts store and they don't have them.. Thank you both for posting this thread and solving a problem.

Roy

Smallblock:
Best to take the alternator apart and remove the trio and take with you. As Ken stated to me they are known by different names. I went to Auto Zone and they had the part for me in 5 minutes (because it was not in it's proper place).

If you have a Chilton's or Haynes repair manual they should have a diagram of the alternator internals. If you're looking for an excellent writeup on how to tear down and rebuild your alternator, go to corvettefaq.com and search for alternators.

Or I supposed Ken could talk you through the process as well, but he basically restated what the writeup did, just in condensed form.

Quick tip: (from Ken to me to you) If you have the quick connect plug on the side of the alternator that plugs into the voltage regulator (should have a brown and red wire coming from it), take a paperclip (as I did) and jumper those two wires out. Someone needs to sit in the car with it running and see if the light goes out or flickers as you attempt to jumper these wires. If it does then you need the new diode trio.

Once I replaced the trio, the battery light came on STRONG (not dim as before) and immediately went back off once the car was running.

Let us know how your repair turns out.

P.S. - I hope there are some alternator guys out there listening. Even though the alternator will show it's charging okay, I think you should still take the time to perform the necessary ohm checks to make sure all of the components are functioning correctly. Power is supposed to flow one way, so the tests have to be performed with leads switched on the contact points to be of value to the tester.

Also, understand the trio will not be exactly the same as what you took out. Looks will be slightly different, but all I did was lay the old one on top of the new one and make sure the spacing and location of the contact points was identical.

|UPDATED|4/25/2004 8:03:14 AM (AZT)|/UPDATED|

Well, I did the test by making a jumper wire removed the plug from the side of the alternator inserted the jumper wire . The red light was on solid started the car and off it went.. Now what does a diode trio look like and where is it located? Sure would appreciate detail instructions as how to replace it...
Thank you
Roy

Before replacing the trio, make sure the alternator is charging. It may not be. If it is charging okay, then the trio is the problem. If not, there could other internal problems. If the light is on bright, it's probably a charging problem, and not the diode. But it could be.

The trio from AutoZone is called the diode trio. Part number is a Wells DO306, the cost is 5.99. Several parts stores will check the alternator for free. Then you know if the output is okay. The light will go out with the jumper when the alternator is not working, as well as when it is. If the output is bad, it needs rebuilt or replaced.

To replace the trio remove the alternator. Look on the back and find a small hole near the center bearing, going through the case. More on this hole later. Take the four screws out holding the case together. There is a front section with the pulley, back section, and a narrow center section. Remove the center section with the back section, and pull them away from the front. You will hear a snap, that's okay. Now look down inside the and you will see two springs and brushes (which are solid) attached to two wires in the bottom of the alternator. You will see where the brushes and springs go into a ceramic type brush holder. Push the springs back into the slots for the brushes.

Put a pin, wire, drill bit, etc, into the hole in the back of the case, and into the small hole at the brush holder inside the case. Just barely start it. Now with the spring in the holder, push the lower brush into the holder, and push the pin in from the back to hold it in place. Now put the other spring and brush in place and push the pin in further to hold that brush in place, and push the pin into the top hole on the brush holder, and leave it there. This will hold the brushes in place when you put the alt back together. Other wise it's impossible. If the brushes are worn out you can get the brushes for 2.39, part number Wells RX103. You can get the entire brush and holder assembly with new springs and all for 7.99 part number Wells RX103H.

You will clearly see the diode trio inside the alternator. It has three tabs on one side and one longer one on the other side. There is a nut holding each tab. Just remove them and install the new diode trio. Fit the two sides of the alternator back together, install the four screws, then pull the pin out of the bottom and the brushes will snap back into place.

If you wish to test the diode trio once it's out, use an ohm meter. Touch on lead to the long tab on one side of the trio. Now touch the other end to each of the other three tabs. Now reverse the leads and do it again.
There should be on current flow, or and open circuit in one direction from the long tab, to each of the other three tabs. When the leads are reversed there should be a nearly equal Ohm reading at all three. If not, it's bad. You cannot do this test with it connected in the alternator.

Ken,
Thank you for the detail instructions and I will have the alternator tested before I replace anything.. I did do another test when the car was running I disconnected the negative battery cable and it continued to run..
Again many thanks to all.. Greatly appreciated

Roy

Back in the days of yor, pulling the battery cable was a fair test. Not good, fair. With the advent of electronics it is no longer a good test.

When you pull the cable you take away the battery from the circuit, and the battery acts as a reference and stablizer for the circuit. Uncontrolled, voltage can jump way over damage threshold for the electronics. The theshold is about 20 volts for the components commonly used in automobiles. I have seen voltage without the battery jump to as high as 60 volts. Before electronic ignition this was not a big problem. The only worry was the radio, and the components were larger and more able to handle the surge.

In a newer car, 1980 and up, you can blow every computer and electronic timer, voltage regulator, radio, control, module, that exists in the car. Very expensive proposition.

Everyone knows someone that did this and was fine. So do I. It won't happen everytime. More often than not there will be no damage. What if it's your turn?

The test also has the same problem as just using a volt meter. You know it's charging but you don't know by how much. It could be just enough to keep it running, or max output. The alternator could be putting out less than 1/3 and pass that, or the volt meter, test. The amp test is needed know for sure.

Ken;
Just wanted to vocalize a THANK YOU! that i am sure will be echoed by hundreds of non writing people. I have been doing this test for years, taught by my dad. Fortuantely, nothing has gone wrong, but i just bought 2 cars this year, both newer than 97, and i shutter to think of the damage$ that i could have done when it can be checked for free..... Who knows how much money you just saved me.
JUST ONE MORE REASON THE SITE IS WORTH THE $10 FOLKS....
dave.