It could be the battery pulling it down, faulty cell maybe. Get the battery tested.

 

Hi,it's not the battery as I've also taken the battery of another car which I know is fine and it did the same

 

Does the battery light work?

All fuses good?

 

Battery light works,comes on when the ignition is turned on and goes off as soon as it starts

 

Are you sure their sending you the correct alternator ?

 

I am sure,but what I did notice is that the one I took off is a clutch less pulley and they've sent me a clutch pulley one and told me it will not make a difference

 

What are the voltages you are getting?

 

13.80 with chargered battery and watch it drop down to 12v

 

And this is with the engine running? with no loads? So to make sure I got this clear. You attach the voltmeter, and reading is 12.6 volts start engine and voltage goes to 13.80 and with the engine running the voltage drops to 12 volts or below? Have you tried with engine running and then putting all the load you can on it and see what happens?

 

The 'clutch pulley' is ringing alarm bells immediately. Not only that the car wasn't supplied with one, but (from a very quick google search) there are two different types of of clutch pulley that aren't interchangeable. And I've seen mention that one type of clutch is 'engine specific' - to address 'damping and vibration'.
An obvious step would be to fit an alternator just like the one Vauxhall supplied.

 

Hi there is this a computer controlled alternator by the ecu?, if you put a voltmeter across it battery it should read a minimum of 12.4 volts stationary, when you crank it it shouldn't go below 9v, typically 10 volts, when its running at about 2000 rpm or higher, it should stay stable between 13.9 and 14.7 volts, check the voltage at the output lead, the thick one, it should be the same as the battery positive terminal, make sure its live with engine not running as well, if you have an open circuit or high resistance on the output lead it wont charge properly, i assume the alternator is actually turning properly as you mentioned a one way clutch....if you measure voltage drop from positive battery terminal and positive alternator output lead, it shouldn't be higher than say 0.5 volt...hope that helps....from Fred in Essex.

 

More modern nonsense, why would a alternator need a clutch? Yet another attempt to take something that's worked fine for 50+ years and break it for no good reason.

 

It is designed to reduce the load of the alternator on the engine. Some horsepoop to do with carbon emissions I daresay. To the OP why not just remove the new pulley and fit the old one?

 

Get your fault codes read. There is a 'control circuit' for the alternator, if that's not functioning then an otherwise fully functioning alternator won't start to output power. Maybe (hopefully?) you'll get one of these:

P0620 Generator Control Circuit Malfunction P0621 Generator Lamp "L" Control Circuit Malfunction P0622 Generator Field "F" Control Circuit Malfunction P0623 Generator Lamp Control Circuit P0625 Generator Field/F Terminal Circuit Low P0626 Generator Field/F Terminal Circuit High

Read more at: http://www.obd-codes.com/trouble_codes/
Copyright OBD-Codes.com

 

Hi I've had none of them codes

 

Sure it's all connected correctly ?

 

I'll check the wiring diagram tomorrow to see what setup is - @Fred Bassett mentioned if it were exactly the right alternator.?

I've had a situ once before where an Astra-H refused to charge as although physically it was the same, it was not compatible with the way in which the ECM supplies the generator switch-on signal and get the alternator charging. Might be worth a look in to 100% confirm the replacement alternator is spot on.

Nick.

 

From looking at the wiring this morning, the alternator switch on signal *is* a duty cycled positive signal from the engine ECM, and the wiring differs from a Z22SE compared to a Z22YH (YH has a feedback signal going back to the ECM also), so ensure the alternator matches your engine specifically, as if the unit is incorrect, even though the ECM is supplying a duty cycle to ramp up the charging on the alternator, the unit may not respond if it's the incorrect type.

The warning light on the dash isn't directly wired to the alternator any more, so even though it isn't charging, if the initial battery voltage is good, the cluster will switch the light off. As @Fire26662 said also, check and confirm the exact battery voltages before startup, when running, and under load - does the alternator pull the battery voltage up to 13.8volts after starting at any point.?

Nick.

 

I can certainly confirm that the battery warning light is just that - a battery warning, NOT a lack of charge warning (on the Z19DTH at least).
When my alternator failed, the warning only showed when the battery voltage had fallen due to lack of charge. A BIG design fault IMO as once one could rely on the 'battery' light to flag a broken belt well before the engine cooked due to lack of water pump drive.

 

Just a few thoughts here, as i understand it the Alternator has prob got 3 wires on, the output lead, big one that goes to the battery, 2 field terminals, now i believe one of those filed terminals should be live all the time, ign on, so check that, you might have a fuse gone, and the earth i believe earths via the ECU using a sine wave as the other gentleman said, so...check for live at one of the terminals, if you can check continuity through the rotor, prob about 4 ohms, or check power in and power out, i think you could ground the outside of the rotor to male it charge full output, and you could get a circuit tester and go from positive to the outside field wire that goes to the ecu, tun it and see i the tester lights or even glows, there is probably an average voltage there of about 5 volts dc... if it son zero all the time prob has an ECU fault...it could very well be an ECU fault, but as the other man says make sure the alternator is the same part number as the one you took off, don't want to take any chanced with ECU's...so check the output lead is live all the time and check one of the field terminals is live with ignition on...then your half way there....hope i have all that right, the best thing of course would be an oscilloscope on the field output terminals, check for sine wave but who has one of those...i don't any more,i used to...well i have a DSO pocket one....and do all the tests re my other message further up from Fred in Essex.

 

Thanks for your replys guys,I've had a couple of days not thinking about it,as its mentally drained me (no pun intended lol) and thought I would spend time with my kids,so after work tomorrow I will look at it again trying all you've said.i did think that putting a clutch pulley alternator on to a car that originally had a clutch less pulley was odd even though the company it came from said it would be fine.i was close to calling the aa out as I have top recovery cover hoping they would come out and diagnose it for me lol

 

The AA might help, but it will depend on the person you get. Home-starts especially seem to be outsourced to the local grunt.
Some will scratch their head (or other bits) and offer to tow it to a garage. Others will say... Ah... it just needs a .... thump ... right there ...(Bang!)... there you are sir, all done - and you'll just hate them for your wasted time and hassle

 

Just got home and put volt meter onto battery 11.11 volts,put volt meter onto back of alternator and have 11.11volts,yes I know the battery voltage is low as I havnt charged it back up from Friday when I was mucking about it with it

 

Battery charged went to start and the starter clicked,so went and got s battery if the wife's Astra which I know is good went to start it click again,getting frustrated now lol

 

Sounds like a bad earth to the engine

 

I've cleaned the one on front of the block and the one to the gear box,is there any more earths on the engine

 

Check the voltages on the starter relative to battery earth post. Then try swart it (turn over) and measure the same voltages. Voltages being the earth of the starter, live feed and solenoid.