Hi guys

I have a Lucas alternator on my zetec. When the engine is running, as the revs rise, the alternator is outputting anywhere up to 16v. Is this going to harm my ecu? Do I need a larger pulley on my alternator? Should there be a voltage regulator on the alternator to cap the maximum output voltage?
Also noticed some acid spillage from the battery recently. Could this be related to the overcharging?

Wow, that's a lot of questions!

As always, any and all suggestions gratefully recieved!

Cheers

Adrian

Is it the standard zetec alternator?

No, it's an ACR one, the same type as fitted to various classics. It's a new recon unit.

Hmm...
Check the Battery first.
Disconnect the Battery, and check the battery voltage when charged. should be 12-13.8V (max)
Mind you if it cranks the engine over and starts and runs the car, the battery should be OK.

It could be the regulator stage in the Alternator has gone Phutt! At least it has some output!



EDIT:
Sort it, or it might cook your battery, and then its even more expense.
Have you checked the fluid levels in the battery?


[Edited on 24/3/2012 by wilkingj]

The regulator should control the maximum charging voltage which at 16v may well damage your ECU and it will cause acid spillage due to overheating of the battery, it will also cause the battery to need topping up. If it's a recon unit get it changed under warranty

Fit a new regulator before it blows every electrical item in the car.
Very easy and cheap to do.

If it is the original Lucas ACR 17 just remove the alternator and take the plastic cover off, unscrew the old regulatot and pop a new one on.

The later Lucas A127 ACR type (sometimes baged Lucas Magneti Marelli) is even easier to repair often without even removing the alternator from the car.


VOLTAGE REGULATOR FOR MANY 12V LUCAS ACR ALTERNATORS | eBay


NEW VOLTAGE REGULATOR TO FIT LUCAS A127 ALTERNATOR 12V | eBay

If you have just got it take it back to the retailer as that's what a guarantee is for

Thanks for the replies gents, I'll get a new regulator and fix it. Looks like the pulley on the alternator may be too small. It's a tiger one, and having read around, it seems they originally made them too small, Which fries the regulator. Surprised, as I've only had the engine running for about an hour or so!

Cheers

Adrian

It won't be the small pulley thats damaged the reg.

The clawpoles of the rotor will expand and contact the stator causing total desructive failure before the reg fails due to the voltage produced. Unless it's a seriously poorly made part. This is probably just internet myth so don't bother hunting around for a new larger pulley until you've changed the reg and retested.

You're looking for about 14.2-14.6 volts charging with a normal amount of electrical accessories runing.

Ain't half a lot of mis-info out on the net, what happens first if you over-speed an alternator is the wiring on the the rotor fails due to centrifugal force.

^ how exactly?

The rotor turnings are spun onto the pole body, then clawpoles pressed over either end, then the whole lots laquered to keep it still, then the wires are welded to tags on the slip ring assembly after pressing.

There is nowhere for the rotor windings to go in an overspeed situation really.

In practice, the clawpole fingers will start to splay outwards closing the airgap between the rotor and stator until eventually contact is made, effectively destroying the stator and rotor.

There may be a lot of misinformation online, but relating to alternators, it won't come from me. I worked in what was the worlds largest alternator factory for 13 years and tested them to destruction, and analysed the results daily for years, this includes 20krpm rotor speed testing when commissioning a new alternator for DC.

Common fault on "reconditioned" A127 alternators is the rotor windings breaking at the joint to the slip ring ---- only thing that can cause that is a combination of poor workmanship and centrifugal force.

It won't be the centrifugal force, especially that close to the centre of the rotor. If the welds are breaking then it'll probably be poor welds in the first place or vibrations, not overspeed.

Atb
Stott