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[jtypecav]

OK. Having read the battery testing guide on here (and elsewhere) I'm drawing a blank.

This is an X30XE running using a Cavalier V6 setup and for many years it's been AOK.

For a few years it's had an issue where the battery slowly goes out of condition, and the alternator is not charging properly. I know there are only two wires from the alt, the excite and the ign live and all connections seem OK and uncorroded.

Here is what the battery is reading from the ECU and is many miles away from the 14+v the Omega and the Vectra have on charge.

The battery is brand new and the alternator was changed 10 months ago (and upgraded from cavalier item to Omega as I'd changed it before already!).


12.4V Not started
9-10-11v on Cranking
11.2 on idle after firing (pre blip throttle)
After you blip the throttle to about 1.5k the needle rises and
it sit's on 12-12.4 again.


Turning on accessories in turn:

Heated Rear Window 12.4
Sidelights 12.3
Mainbeam 12.1
Wipers 11.9
Blower 11.7

All off -

Back to 12.4

There are no other gadgets or bells or whistles and the blipping the throttle and the battery gauge going up to 12v after starting makes me think the alt is at least doing something!?

Any help greatly appreciated.

Also noticed that the idle air control valve is vibrating (even with ignition off) and the full beam tell tale no longer works even though I renewed the bulb.

As I say the car has been fine for around 4 years, but past couple have been trying esp, when our weather is so atrocious at the mo.

[allen25]

Not sure if it is any help to you but I have a new battery on my V6 and the alternator has been replaced a few thousand miles ago. I don't have the readings from when I had the issues but currently:-

Not started 12.34v
Started - tick over at c500 rpm 14.2v
Started - tick over at c500 rpm, rear screen demister, headlights and heated seats on 13.9v

I don't have any more stats but may help you diagnose.

[tidla]

Theres a step by step guide in the maintenance section by Mr wood.

Does the alternator warning light illuminate?

Do you have a voltage on the exciter wire?

Check for volt drop while running between the battery negative terminal and the engine block, likewise with the positive terminal to the thick supply wire on the alternator.

Your looking for a missing 2volts.

[Kevin Wood]

Also.. Your post implies that you are relying on the voltage reading from the ECU. I wouldn't trust it. Measure it directly at the battery terminals with a multimeter.

On the face of it, though, it doesn't look like it's charging.

Loose crimps where the cables meet the battery terminals is a favourite.

[2woody]

the normal running voltage should be 13.8 or very close thereabouts.

[symes]

agree with 2woody your voltage should be 13.6-13.8v

[tigers_gonads]

Yup, not charging 

Check the crimp terminals at the alternator and battery 

[jtypecav]

Thanks guys, will get on this. Old multimeter got soaked when the shed roof leaked, so have ordered a new one and will get checking earth crimps and voltages shortly.

Just hope it survives a weekend in the peak district! Praying for daylight and no rain! 

[Vitaliy]

95% certainty its alternator. There is a guide somewhere here how to open them and replace regulator/brushes pack. Easy enough to do - never needed guide myself.

[Marks DTM Calib]

I would expect to see nearer 14-14.2V given the charging system was designed for Calcium lead acid batteries which require slightly more V's.

Either way, the readings you ahev are low but also not trustworthy if they are ECU figures.

[tigers_gonads]

If the crimps are ok, see if you can get a part number off the regulator on the alternator and replace that 
Hell of alot cheeper then replacing the complete unit