Low voltage output to battery - 13.3 volts

[sam80quattro]

lol

[Jamo]

lol

What's so funny?

[popdemonic]

Jamo,I have been experienced kinda problem on my UrS6.Firstly,I got the New VR on Alt but no luck.Check the + wire that running from Alt. to Starter,sometimes the Joint on the Starter has come loosen.So It causes you see lower Voltage on battery.
Well,When I turn on HIDs.I tihnk it's normal to see the Volt Gauge on the Cluster drop ~1V.They also drop when the 2nd Fan step activated or
Air Con is turned on.Sometimes with much loads on the system,I see 11.8-11.9V on the gauge(At night).IIRC,the gauge on the IC will show the Voltage lower than actual if measure with DMM.

[sam80quattro]

What's so funny?

Take it your batterys in your volt meter are ok they start giving poor reading when they are flat.

vdo volt meter?

[GazzaG60]

id expect you have check or isolated the interior/boot lights maybe underbonnet too.

sounds like the alternator . mine never drops below late 13's. i have no aircon though.

[pixsaudisex2]

vdo volt meter?

I seem to be getting a low voltage to the battery, on a multimeter I'm only registering 13.3v

Any ideas on what the problem could be?


like he says mulitmeter.. always start with the basics...

[Jamo]

The title says 13.3 volts should make you think i used a voltmeter

[johne]

The dashboard voltmeter is useless for this sort of work. It's not accurate - although you can adjust it from the back - but more importantly it can only measure the voltage at the point it sits in the wiring loom which will not be the same as the voltage at the battery or the voltage at the alternator. For instance it does drop around a volt when you switch on the headlights but that doesn't mean the alternator voltage has dropped by one volt or even that the voltage at the headlights has dropped one volt.

The only way to measure voltage is buy a digital voltmeter - under £10 from Maplin - or borrow one and measure the voltage actually at the back of the alternator and again directly across the battery terminals.

If you want to check how good the wiring and the earth is betwen the alternator and the battery, put a long length of wire - can be as thin as you like - on one of the DVM leads and measure the voltage between the alternator +12v terminal and the +12 volt terminal on the battery. It should read as close to zero as possible. Do the same from the alternator body to the battery -ve terminal. Anything more than 0.1 volt in either test and you've got a poor wiring connection somewhere to track down.

John

[Phil Payne]

I like the Draper DMM5 - AFAIK it's the only "budget" meter with a direct-reading 5-cylinder tacho scale.

[Jamo]

Just like to point out I have got a voltmeter and used it can't do years of ICE and computer building without one

I've had to swap the battery for now this person has the same issue as me, the optima needs a high voltage to charge http://www.detomaso.nu/~thomast/alternator/

I have a new VR going on the car as well and I will be doing a 0 gauge earth strap

[johne]

Just like to point out I have got a voltmeter and used it can't do years of ICE and computer building without one

I've had to swap the battery for now this person has the same issue as me, the optima needs a high voltage to charge http://www.detomaso.nu/~thomast/alternator/

I have a new VR going on the car as well and I will be doing a 0 gauge earth strap

The guy in the post has a problem that applies just to his car because he's got an ammeter. We don't have that scale of problem because we don't have ammeters on our cars.

John

[Jamo]

He had the same problem low voltage non charging of optima battery which is part of the reason why I was looking into it.

For now I've got a bosch one in

[s2driveruk]

ever get to the bottom of this one Jamo, just managed to fire mine and looking at poor charging/voltage on the guage but need to start closing out the issues with a DVM.

[johne]

Ignore the gauge in the car.

Put a DVM directly on the battery terminals with the engine running & hopefully you'll be getting 13.6 or better.

Put the same DVM across the back of the alternator (alternator body and the stud holding the heavy cable lug) and if the reading is more than a 0.1 volt higher start looking for poor earths/wiring.

John

[s2driveruk]

Ignore the gauge in the car.

Put a DVM directly on the battery terminals with the engine running & hopefully you'll be getting 13.6 or better.

Put the same DVM across the back of the alternator (alternator body and the stud holding the heavy cable lug) and if the reading is more than a 0.1 volt higher start looking for poor earths/wiring.

John

Hi John,

Ok, so before cranking the car on the batter terminals about 12.9
once started its about 14, will all the key electrics on it drops to about 13.1-13.3 so that all seems pretty healthy I guess.
At the Alternator with no load it was all over the place but around the 15v mark - is that right?

Cold crank was very laboured so will get under the car and check for the health of the wiring to the starter - any other pointers much appreciated, otherwise i guess its time for a lamp and pulling fuses right?

Cheers
David
(electrical numpty )