15 replies to this topic

[Joebutt]

Hi all, hope someone can shed some light on my little problem. I've just fitted New alternator to my 1990 studio 2 and it's only giving me about 11.5 volts. I can't see any loose connections. Has anyone got any ideas ? Thanks

[sonikk4]

Where did you get that figure from exactly??

[Wise Old Elf]

You need to check the battery voltage with the engine not running and then with the engine running.

[sonikk4]

Did you take that reading with an ammeter off the back of the alternator.

[Cooperman]

If the alternator is only giving 11.5 volts with the engine running at over around 1800 rpm, then the new alternator is defective with a capital F.

[Wise Old Elf]

Prob just battery voltage. I would check that the alternator is being excited before condemning it to the scrap bin.

[Joebutt]

The voltage reading was taken at the back of the alternator. Do I need to excite the alternator (only asking that cause I never have when fitted alternator to other vehicles in the past) If I Do need to how do I do it ?

[KernowCooper]

Your ignition light on mini type alternators provides the voltage to the alternator to start it charging, is your ignition light working before you start the engine and then going out fully once started. Sounds if all the wiring is connected a faulty alternator.

[Joebutt]

Thanks Sparkie, the ignition light is working as it should so that sounds like the alternator is no good.(bigger) Is there any way of exciting it with another feed or will that not work ?

[Joebutt]

(Bigger) should read (bigger)

[sonikk4]

It does sound like its shot and it does happen. I have been there myself with replacement alternators (on my old RS) take it back and get a replacement.

[Joebutt]

Thanks for the help Will pick up new alternator at Stoneleigh tomorrow.

[sledgehammer]

I would also check with another volt meter (if you have one to hand)

 

& check the spade terminals in the alternator area

 

with the engine running does the engine revs drop when main beam lit & heater on ?

 

do light brighten when engine revved ?

 

best of ...

[Dusky]

My new alternator was faulty also( bad bearing) . Minispares supplied a new one instantely :)

[Wise Old Elf]

You need to unplug the alternator and check the exciter wire (small wire) is supplying battery voltage to the alternator. Without this the alternator will not charge.