Voltage strangeness - regulator ???

Hi everyone,

I just went to BatteryWorld and got (can you guess? can you?) a new battery. The guy there stuck a voltmeter on it to check it was getting charged properly. He found that the voltage was high while idling (14.8V) and low while revving (13.0V). He said that my shiny new battery probably won't be getting charged much while I drive around. Is this a regulator problem?

More a voltage drop problem

The fact your reg is putting out 14.8 at idle says to me it is ok

Dubs are not known for there generous generators.

Steps

1) re do ALL your earth points - including battery terminals. Take them off and clean them up. Make sure you have an eart strap - Amazing number have lost them over the years!

2) Convert to alternator. They put out more amps

Thats Odd, should be the other way round, I don't know what the problem is, though, if I had the problem I would diagnose by substitution It would be a good idea to fit a voltmeter otherwise try idling with all available accesories & lights switched on & when you rev it a bit the headlights should go a bit brighter, if what the guy says is right, they would go a bit dimmer, sorry but that is all I can think of without spending money

Blue74L message wasn't ther when I started this, he typed quicker than me, eart (eart) strap is a big issue, I thought you had an alternator?

[Edited on 12-3-2003 by kombikim]

I'm assuming I have an alternator: it's a '75 2L kombi - sorry for not knowing much about this stuff!

Earth strap is there but looks very old, and I think that a lot of the cores at the chassis end could be broken from years of flexing (hard to tell under the insulation, but it wobbles very easily).

The best straps are the flat braided copper ones. Ususally located from Gear box to body and battery to body.

You need one of those viscious claw washers under them to really dig in and get good contact.

2L motors almost always have alternator
I have also run an earth strap straight from the battery terminal to the bolt on fan housing closest to battery

Thanks guys, I'll beef up all the earthing. I hope it does the trick!

If that don't work, check your brushes (and commutator) - if they are in poor condition, the increase in speed could cause them to lose effective contact.

If the brushes look sick, but are of a good length, you can clean them up on a bit of sandpaper. The commutator can also be cleaned up with fine sandpaper, but you need to ensure the insulation material between the pads is below the outer surface (or they'll lift the brushes.) The old - fashioned method is to grind an old piece of hacksaw blade to the same thickness of the slots, then draw it through the slots until they are cleaned up.

70AutoStik wrote:If that don't work, check your brushes (and commutator) - if they are in poor condition, the increase in speed could cause them to lose effective contact.

If the brushes look sick, but are of a good length, you can clean them up on a bit of sandpaper. The commutator can also be cleaned up with fine sandpaper, but you need to ensure the insulation material between the pads is below the outer surface (or they'll lift the brushes

I'm not trying to be pedantic here, but since he has an alternator he doesn't have a comutator - he has slip rings.

Alternators work "inside out" compared to generators - the spining part carries the low current field windings (via small brushes and smooth slip rings) and the fixed outer windings provide the charging current.

Alternator brushes take a long time to wear out as they are running on smooth slip rings and so don't spark like the generator comutator does.

Still worth checking though.

The 75 alternator has an internal regulator, so should have just two connections on it - a thick red one direct to the battery, and a thinner one (probably blue) to the dash light. It is interanlly earthed, so there is no erth wire, but as other have said above, the earth straps for the battery and tranny must be in good condition or weird things happen to the electrics.

The dash light MUST work for the alternator to charge - if the bulb blows, the alternator looses it's "sensor" current and won't charge.