Gen 2 Exciter Circuit Diode Question(not the trio in the alternator)

[Refalgren]

Have a question for the experts here. Yes I did a search, but couldn't find the answer. How do I tell if the Gen 2 Exciter Circuit Diode (the one at the top of the underside of the dash) is good? I'm horrible with electronics, but this is what I did. Using a Fluke 75 multimeter, I did a continuity test (the cathode symbol followed by the sound waves?) and got .0L going one direction, and .551 on the other. I don't know if this is a good thing or bad though, because I don't know what the specifications for the diode are.

 

[tim292stro]

Sounds like it's working. If it was bad it would show either OL both ways or something less than 1MΩ/2V both ways. Semiconductors fail either open or shorted.

The sound (continuity)/Diode test mode will put a current limited power across the diode you are testing. The number which is displayed is the forward drop of the diode, from 0.551V, that sounds like a good Schottky diode. Standard rectifier diodes will usually measure out at 0.7V, and some of the low V[SUB]Forward[/SUB] Schottky diodes can measure out at 0.4V or slightly less (actual specs are in the datasheet for the part you use).

 

[Refalgren]

I think this is an original motorola diode. It is black and silver with a circled "M". The semi-congealed/seperated duct tape I removed looked ancient.

Even with it being good, i'm having to rebuild this alternator a fourth time. It tested bad today. Again... Going to make sure that the next shop I take it to does a complete job this time and do the whole 27SI kit etc. The last shop that worked on it only replaced the diode trio and the rectifier.

Any recommended alternator rebuild shops in or around Mobile, AL?

 

[tim292stro]

I'm on the left coast, sorry. They aren't too bad to rebuild yourself if you have tools, time, and patience...

 

[Tow4]

Even with it being good, i'm having to rebuild this alternator a fourth time. It tested bad today. Again... Going to make sure that the next shop I take it to does a complete job this time and do the whole 27SI kit etc. The last shop that worked on it only replaced the diode trio and the rectifier.

These alternators are very easy to rebuild. Here's my rebuild thread with pictures.

http://www.steelsoldiers.com/showthr...rnator-Rebuild

And I also sell the rebuild kits.

http://www.steelsoldiers.com/showth...r-alternator-p-n-1105500&highlight=alternator

 

[Refalgren]

Sorry for the late reply Tow4. Check your inbox.

 

[addinquir]

Where is that diode in the 1008 charging system.

I need to know where the diode is located that everyone is talking about is so I can finish diagnosing why I am not getting my Gen 2 to charge even though the alternator is in top shape. The problem in the wiring from beginning to end and I need help finding the problem.
I checked the relays under the dash, checked all my connections and cleaned them, did all I could just short of bringing it to a shop but I am a mechanic and I can do this but I need help before I tear apart the whole electrical system!

Sounds like it's working. If it was bad it would show either OL both ways or something less than 1MΩ/2V both ways. Semiconductors fail either open or shorted.

The sound (continuity)/Diode test mode will put a current limited power across the diode you are testing. The number which is displayed is the forward drop of the diode, from 0.551V, that sounds like a good Schottky diode. Standard rectifier diodes will usually measure out at 0.7V, and some of the low V[SUB]Forward[/SUB] Schottky diodes can measure out at 0.4V or slightly less (actual specs are in the datasheet for the part you use).

 

[MarcusOReallyus]

The Helpful Threads sticky is a wonderland of information, all nicely indexed for you!

There's even a thread on diode locations.