Club 80-90 Forums

Hi Folks

I have a problem with an overcharging alternator, it's outputting 16v while driving, my normal output is 14 up to 14.5.
The Battery indicator on dash is also remaining lit all the time.
No problems starting, no problems with lights, blower motor, wipers etc, all electrical things working ok.
I have a analogue voltmeter on the dash that I've checked is accurate and correct, shows starter battery level.
I have another digital voltmeter showing leisure battery level, working and accurate too.
Is there more earth points to check than I've mentioned below that would point to this problem?

Things I've checked so far are......
1. Replaced the voltage Regulator , made no difference, replaced it again (just in case i had a faulty still no difference
2. Using a jump lead, I checked the earth from alternator bolt to negative terminal on battery, made no difference.
3. Connected negative terminal to body, made no difference.
4. I've checked the wiki for symptoms and found this http://wiki.club8090.co.uk/index.php/VW ... r_checking" onclick="window.open(this.href);return false;,

anyone had a similar problem or hazard a guess whats going on or suggest things that I could try?

Faulty rotor in alternator. Can't think of anything else

Possibly a faulty diode pack, the diodes drop the voltage running through them, if one or more is short circuit you get a higher voltage output than the regulator thinks often the alternator makes a humming noise.

Tis possible to change the diode pack yourself if you want to save money

thank you guys,
Good to have a bit of info to start eliminating things, I'll look into it tomorrow and let you know if I make any progress

If the diode pack was faulty, would that cause my battery to drain or not necessarily?

Toc wrote:If the diode pack was faulty, would that cause my battery to drain or not necessarily?

It can do.

ok, my battery is holding its charge no bother, still could be a diode pack problem though eh?
do you know Is there a way of testing it with a multi-meter without taking the alternator off or will it have to come off?

Toc wrote:ok, my battery is holding its charge no bother, still could be a diode pack problem though eh?
do you know Is there a way of testing it with a multi-meter without taking the alternator off or will it have to come off?

Only with a scope you will see an intermittent AC signal as the phase the of faulty diode passes a reverse voltage.

Check the voltage of the blue wire terminal of the alternator, if it is high or higher than the alternator output terminal that would be a sign.

ok cool, thank you

Got the alternator reconditioned, the problem is sorted now.
Thanks a million for your help guys, again !!