Alternator failure, no charge light

[expresso bongo]

It looks as though the alternator on my 1996 SGL5 has failed. All the electrical services began to fail/dim whilst driving after a very reluctant (low cranking rpm) restart. The charge failure warning light did not illuminate but, being a negligent sort of fellow, I couldn't tell you whether it lit before start-up!
On return to base, I found the battery voltage, engine idling, was 12.2-plainly there was no charging taking place.
I've had a poke around and found that the field appears to be working-it attracts a screwdriver and the voltage at the field terminal is around 12.2.
I charged the battery for half an hour and started up without difficulty. The output voltage at the alternator was then 12.54, the voltage at the battery terminal 12.45 (yes, slightly lower, not a typo!).
It seemed to me that the led on my output tester was flickering, perhaps indicating ac and thus a diode failure.
It also seemed to me (subjectively, of course) that the alternator was very hot. I wonder if a failed engine-bay fan could lead to overheating and diode failure.
The belts are fine and there's no mechanical noise which would indicate a bearing failure.
Is it possible to replace the diodes without recourse to a reconditioned unit? I'm fairly handy with the soldering iron (I repaired the aircon fan resistor pack several years ago) but potting etc would probably not be something I would undertake.
I am concerned at the failure of the charge light. Is it possible to check the bulb without stripping out the instrument panel?

[Simon Jones]

You have PM

[expresso bongo]

Many thanks for the "heads up", Simon. I bought the alternator for £20, collected it at 20:00 last night and fitted it this morning.
Caramba! All is well; truly, the Cosmic Supply Company is an efficient and economical institution (and you are a diamond geezer!).
The warning light filament was intact and it now works when the ignition is switched on; it seems it does not necessarily light if there's an internal failure in the alternator (I knew that, but why do I always get the atypical failure modes?).
Thanks again,
E.B.

[Simon Jones]

Good news. I bought some bits of the same seller last night too & did mention he might get a call from you about the alternator. All's well that ends well

[expresso bongo]

Well, it seemed that way, but after maybe thirty minutes running the replacement alternator packed up; see my new post on "radio clicking".

[Simon Jones]

Not such good news . It does seem like there is an under lying fault elsewhere in the electrics to result in 2 alternators packing up.

[Darkstar]

Mine did the same ( No warning light) which threw me out at first until it was suggested possible alternator failure, took a bit of convincing, as all previous cars always showed some sort of warning light, maybe its just "that Bongo Thing"

[Northern Bongolow]

http://www.igmaynard.co.uk/bongo/forum/ ... alternator

[expresso bongo]

I had both the old and "previously-cherished" alternators repaired. I've fitted the original and all is now sweetness and light (especially light, as the charge light comes on when it should!). The radio glitch remains a mystery.
If you're near Portsmouth, you need look no further than "alternatorman"; he collected my alternators, got the parts (diode packs), repaired them (including new bearings) and returned them to me withing 48 hours. The cost? £70 each! I've fitted the original alternator and now have a serviceable spare. Both come with a year's warranty.
E.B.