Discharge light on at low revs?

[Niels Svane]

Hi everybody

Since the early spring where I replaced some electrical parts, and cleaned the carb, my 83 R4, 845cc has run perfectly.
Now after a lot of driving the last two weeks, the discharge lamp lights up at low revs, and I measure about 12.45V on the battery (at idle).

Do you have any suggestions to why it suddenly goes on? Its usually after 2-5 mins driving, and goes away on trips over 100km - So it seems a bit erratic. Ive checked the different connectors, and they seem fine, and the large negative cable from the battery is the only part that looks a bit worn - But that it has done all the time

Is there any particular area I can check/measure?

Yours
Niels

 

[Niels Svane]

So its with a generator/alternator instead of a dynamo

 

[jonigel]

Hello
Alternators should put out 13,5 volts so if you have a later type alternator the diodes on the back are failing or on the earlier type it could be the control box ,but i think they are sealed for life
Hope this helps

 

[mr-reno-139]

The early cars fitted with alternators 76 to 1980 did have separate regulator box not sure that they had a warning lamp just voltmeter on dash ?
Later cars had more conventional type with the voltage control built in I suspect alternator faulty but it is possible to remove brushes on some makes of alternator easily
Valeo/Paris rhone are available as an assembly with voltage regulator built in
However it may be simpler to replace alternator
Found this as an example

 

[Niels Svane]

Hi
Thanks for the replies
I really hope its just a faulty wire somewhere but ive checked them all. And no lights seem to be drawing too much power as the haynes manual suggests.

I'll try driving some more, and see if it continues like this (charge at 1000+ rpm)