alternator overcharging- has to be the reg or not?

[steveo3002]

polo alternator charge is going mad fluctuating between normal and 15-16v 

 

just looking for a bit of reassurance that a new reg should sort it ....or is there other internal gubbins that might be to blame? 

[Richard]

Regulator would be the first thing to try. There's a seller on eBay called Gold Lion or something, he has posted loads of 'how to' videos on how to test and repair alternators.

[steveo3002]

yeah cheers ...reg is easy to do , its just im a bit bolloxed if it doesnt cure it as the other chariot is off the road too

[cros]

Ive had 2 alternators fail this year, both undercharged until I replaced them when I was overcharged.

[Des]

If you've the reggy brushpack assy it's rather easy to change, usually in situ, but do just check the reg has good connections first, might be fixed by just tightening screws.

[dollywobbler]

Yup, definitely check connections, and engine earth points. My 2CV overcharged and killed the battery. On these, it's a separate regulator, which wasn't seeing a good earth, so wasn't restricting the alternator output sufficiently. Only time I've killed a battery stone dead.

[twosmoke300]

Are you using a digital multi meter ?  Be worth checking the battery is going flat on that as they tend to read high on volts when they do.

Guess how I found that out .

[steveo3002]

still the same with a new reg/brush pack

 

guessing theres other internal bits that can make it overcharge

[castros_bro]

Unlikely,   The only other electrical bits inside are some coils of wire which generally are robust but if they go wrong ie go open circuit then there is bugger all electricity produced.   A simple explanation of how it works is the battery voltage is used to power up the regulator which produces the control voltage to the exciter coil - when running the output of the power coil is monitored and the voltage to the exciter coil changes to control the output of the power coil. 

There has to be good clean battery and earth/chassis connections.

[Richard]

There's the rectifier/diode pack too, although I think you normally get reduced voltage if that fails.

[twosmoke300]

Check your meter!

[steveo3002]

meter is accurate enough , i can hear the heater fan go hyper when its showing 15v 

 

dunno what to say...going to try another alternator , all the leads are a1 as ive replaced them all during a engine swap

[dollywobbler]

Have you actually checked all of the wiring and earth points?

[steveo3002]

yep...its a very basic car ,all good 

[castros_bro]

Hi,

 

Fitting different cables does not mean they are good cables nor the connections are good. It is frustrating to try and explain electrics to a mechanic as they cannot see physically see what is happening.

 

I take suspect alternators (without the vehicle)  to a little local company who run it up to speed and test it for output regulation under load for £5. Diagnosis via interwebs can only go so far.

[steveo3002]

yeah fair enough , i made the cables myself , all new thick cable crimped ends with a hydraulic crimper , all good as far as i can tell , ends are tight and free from corrosion

 

are you saying if the wiring is somewhere hanging by a thread , then the regualtor will allow it to go way above 14.4 ?    not arguing here i thought thats what a regulator does ?  it shows same reading at alt /batt /differant earth locations etc

 

wanted to upgrade to a bigger amp one anyone so no money wasted 

[dollywobbler]

Yup. If the regulator cannot see a good earth, it can't see the 14.4 volts to regulate it. Not saying it's definitely the issue for you, but it was for my 2CV. I was able to test that very easily by making my own earth cable between the regulator and the neg terminal on the battery (the regulator is mounted away from the engine, which makes it a bit easier to do).