I suspect alternator failure

[humptynumpty]

ok for a few days after car started battery light comes back on for few3 seconds then off and no problems but today 30miles from home it is now coming on everytime i go above 1200revs, the battery is holding charge of 12.06 and down to 11.39 when engine running, all cables look good but when plug on top of alternator was disconected the light on dashboard never came on when ignition turned or engine started, so i drove 30miles home at 40mph in 5th gear so light never came on also a few days ago i got battery light and charging fault warning when i accelerated and turbo kicked in and upto about 3000rpm

[Nunfa1]

With the engine running and a voltmeter across the battery terminals you should be reading approximately 13.5-14v. As you've only got 11.9 then I too suspect the alternater has died.

Is it possible to get a diode pack for these or does the whole unit need replacing?

[humptynumpty]

if it has died it wouldnt charge at all would it, its just above 1200revs the problem also the belt isnt the best but it is tensioned well

[Nunfa1]

In order to charge a 12 volt battery you need more than 12v, that's why alternators are around 13.5-14v. If you're only reading 11.39v across the battery with the engine running then the alternator is not going to charge the battery.
Do you have access to another car? Maybe your meter is a bit out? Try it on a known working car and see what it reads.

[humptynumpty]

battery is holding 12.06 volts with no drops and muter is digital and new, what is top plug on alternator for

[Nunfa1]

Originally Posted by humptynumpty

battery is holding 12.06 volts with no drops and muter is digital and new, what is top plug on alternator for

But isn't that with the engine off? With the engine running and your meter across the battery terminals you're actually reading the alternator voltage, assuming everything is connected correctly, and this really needs to be above 13v.

It is strange though, given how much driving you've done there must be getting some charge in the battery.

[humptynumpty]

yeah 12.06 with engine off but car running its 11.39 but light and warning only come on above 1200 rpm

[Mark2000cc]

Alternator, definitely.
I had exactly the same problem. If you go into your dash diagnostics you will get a true reading of the volts, do a search as I can't remember what number It is on the dash. Anything less that 14 volts and your alternator is shot, it can gradually die. I got a new one fitted and jobs a good un, not cheap though, just over £300 I'm afraid.

[humptynumpty]

i just checked again on tickover its charging at 11.59 with just engine and 11.39 with wiper and lights on and diagnostic said bat held 12 before engine started

[Mark2000cc]

Post 3 mate
http://www.the75andztclub.co.uk/foru...nator+charging