Alternator woes ?

[kenthepipe]

Iv'e recently noticed that the red warning light at the bottom of the battery gauge is lit all the time and no reading from the needle ie it just stays at the bottom of the scale, no other faulty lights on the dash. In the past I usually just blip the throttle and it springs into life but alas not now, the battery is quite old now (5 years) and was quite low although I always take care of it regarding charging etc, I charged it up and it's holding a good charge at present, anyone got any pointers, although if it's the alternator my garage will have to take it off, and hopefully if it is that send it out for recon ?

Ken
80 928 S
5 Speed

[tr7v8]

If the light is glowing dimly it is normally a case of one of the diode pack going leaky.
If it is stopping charging I suspect the brushes are knackered. Blipping the throttle probably moved them enough to make contact. Time for recon alternator by the sound of it.

[stratfordshark]

No volt reading at all is odd as you'd at least be reading battery voltage even if alternator not charging.

Have you got a multimeter to test voltage at jump post? To start with compare the voltage reading there with what's showing on the voltmeter.

With car started, if alternator ok you should see around 14V if engine revved to 2000rpm.

What readings do you see?

[kenthepipe]

( I don't have any reading at all from the original gauge on the dash pod, so nothing to compare with ? )
Is it possible to get a reading from the "jump post" to the number1 pin at the 14 pin connector, I believe that No1 supplies the "exciter" wire to the alternator ?
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With car started, if alternator ok you should see around 14V if engine revved to 2000rpm.
What readings do you see?[/quote]
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Have not been able to establish this yet, think it would be helpful with 2 people.
Today I contacted the garage that has worked on this car for 28years the owner is a good friend but currently in Italy, he's back on Thursday and asked me to contact him then.

[stratfordshark]

Just compare the voltage on the post with the bottom of the range on the gauge (8V, 10V?). Do the readings agree?

To test alternator output just rev slightly at throttle quadrant as you measure voltage at post. It’s a one man job that way! Or just clip multimeter lead to post and place meter in position you can see it when standing by driver’s door and prodding pedal.

[kenthepipe]

Thanks for your help , I will update this post when I have some news.

[kenthepipe]

Not conclusive yet, but my friend rang to say they had the alternator off, and both brushes are unevenly worn with a few score marks on the stator inside the alternator. I thought it was a good opportunity to bring the alternator home and give it a good clean to match the rest of the underside and the cool air cowl and hose are still relatively new so they'll all match up when re-fitted.
Alternator is going for re-con next week, so I will post any results I have.

Thank's

[kenthepipe]

I got the re-con alternator back yesterday, exceptionally pleased with it, I thought it was a brand new one when I opened the box, the original pulley on the front had a small chunk of metal missing although it did hold the belt ok and the rotor fan behind it was a little bit worse for wear, new rectifier and machined the stator, all outer casing refurbished etc.





Thanks...,

[stratfordshark]

That looks superb.

Now for the fun of reinstalling if you’re working by yourself. Good arm exercise!

[kenthepipe]

That looks superb.

Now for the fun of reinstalling if you’re working by yourself. Good arm exercise!

Yes I couldn't believe it was the same unit, exceptional job, just hope when it's installed it works as well as it looks.
Fortunately it's at my friends workshop high up on one of his lifts, infact he just left it there all week and he'll fit it next week. Unfortunately my "spannering" days are limited now due to arthritus in my finger and wrist joints, that's why sometimes I wish my 928 was an automatic and not a 5 speed

[kenthepipe]

Well, all up and running smoothly now, one little hiccup we had while fitting the black air cowl to the back of the alternator was there were hardly enough threads sticking out to fasten the air cowl to, answer was to remove the plastic vented piece they had attached, once that was off the air cowl fitted perfectly.