Charge Light Problem

[colinham]

The ignition charge light on my 91 S2 is staying on all the time, Ive checked the alternator
and its charging and belts are Ok, is there a voltage regulator relay in the circuit somewhere that might have failed. My fuse box lid is damaged and I cannot make out the names on the various relays, can anybody point me in the right direction as to a possible cause and if a relay is suspected can you identify it for me, thanks

Colin

 

[Mike_Pollock]

How did you check the alternator output, as the regulator is built in to the alternator?

 

[ukmastiff]

I would like to know exactly what voltage reading you get if you put a voltmeter accross the battery with the engine idling with headlights on and off. I would also like to know the same answers with the engine not running.

Regards Mas

 

[colinham]

Hi

Iam not very good with the electrics, I just put a meter across the battery terminals and as the engine is revved the reading goes from 12v to around 14v, so I assumed the alternator was OK, any ideas of a fix welcome.

Colin

 

[robwright]

It should show more than 12V when the engine is idling. The output has to be more than 12V in order to charge the battery. Any less and charge starts flowing the other way. That is essentially how the ignition light works. And Mike is correct the rectifier and regulator is built on to the back of the alternator but is replaceable as a unit.

 

[Mike_Pollock]

As Rob says, would add that the carbon contacts - brushes, if you like - come as part of the regulator assembly too, and can wear very unevenly.

Once the alternator is off, its only 2 screws on the back to remove this assembly.

 

[zcacogp]

AS said, it should show over 13v when idling without any load, and anything less will be your problem.

Changing the regulator can give a short-term fix, but if the alternator is that old then you may find that something else in it fails soon afterwards. New alternators are (painfully) expensive, but a good automotive electricians may well be able to rebuild your existing one for a fraction of the cost of a new one. It's well worth shopping around a bit and asking nicely. (I think there is also an alternator from something else that fits straight on and is much cheaper. Check the Alternate Parts thread.)


Oli.

ETA: Looks like I was wrong about the alternate alternator - sorry. This link:

http://www.alanara.fi/Possu/ENosat.html

.. lists a replacement for early one but not late ones. But it does give a Bosch part number, and they may be cheaper than ECP/OPC/GSF etc.