Sign in to follow this  
Followers 0
Jamez3

A8 alternator fault - now car won't start??

14 posts in this topic

Hi,

the battery failed me about a week ago and with it being 7yrs old I thought I would charge it up but replace with a new one. Drove to my garage and they said its the alternator not the battery. I have been advised that the alternator on mine is not common but I could use a 120amp instead of the 150amp previously fitted. Whilst driving back home to source an alternator the battery failed again and the car spluttered and coffed to a stop in the middle of rush hour traffic! Fired up after a couple of mins but was mis firing and auto box was struggling just to get to the side of the road?

The A8 was transported to the garage and a 120amp alternator was sourced and fitted but now the car turns over but will not start? Any ideas? Have I damaged something whilst forcing the car to the side of the road??

All help appreciated.....

Share this post


Link to post
Share on other sites

Broken alternator can very easily kill a battery.

Could be:

1 - Battery

2 - Bad Earth

3 - Bad +ve terminals (search for Figure11's posts on this)

I'd say to be careful with the 120A Alternator. Your car probably has the 150 fitted for a reason. a8parts will probably be able to get you a used replacement that's the same model as yours.

Share this post


Link to post
Share on other sites

PsYcHe ....thanks for your reply.

I have left it with the garage over the weekend. Apparently the car is trying to fire up but just keeps turning as if no fuel or no spark?

The 120 amp alternator supplied is supposed to output very near to the original 150amp that was on the car ( Im not a techie ). I will know more Monday.......

Share this post


Link to post
Share on other sites

This car needs a lot of amps from time to time.

150-120 = 30 which is 20% less. Whoever told you a 120 gives almost as good as a 150 doesn't know his amps from his ar*se! LOL

Basically you will upset the balance in the electrical system. At peak the car is expecting around 150, gets only 120 - something has to give!

However alt output has not got not a lot to do with the non starting but the demise of the old one may have upset the computer somewhere.

Get it on VagCom and you will probably learn what's up.

I'd replace like with like in this instance.

Share this post


Link to post
Share on other sites

had something like this happen to me when i fitted a new alternator to a 2.8 facelift d2 of my friends.

fitted alternator and car would fire then ccut out right away.. it was the immobiliser not turning off which caused the problem

what i did was disconnected the postive terminal from the battery then kinda sparked it of the terminal a couple of times before fitting it .. this worked for me and got the car running

Share this post


Link to post
Share on other sites

I jumped through a lot of unnecessary hoops before I found my earth fault.

My thread is here.

In the end you can bowl out a few issues with a volt meter.

Firstly take the volts at the battery across the terminals - should be above 12v if battery is good and fully charged.

Next take voltage from starter motor connection on front chassis rail drivers side. Earth on the chassis - should be above 12 volts.

Then earth on engine - should be no voltage drop. If there is then check the engine earth strap, clean all the terminal and recheck.

Try jump starting with a known good battery at the front with the earth jump lead clamped to the engine.

Once the engine is running take voltage reading direct from the back of the alternator to the engine earth - should be 14V +

Then take a series from alternator to chassis, across battery ect. they should all be with .1V of each other. Any big deviations and you have a poor connection.

No voltage at the alternator and the thing is duff.

You can get by with a 120 Ah alt but it will struggle on a cold morning with all your heated seats, full beam and so on.

HTH

Mike

Share this post


Link to post
Share on other sites

Thanks for your replies.....unfortunately the car is still with the garage and they haven't looked at it yet due to prior commitments? I will advise them of the immobiliser issue because that sounds most likely ( fingers crossed ). I raised several concerns about the 120amp versus the 150amp and I was advised there shouldn't be an issue??

As soon as I know more I will update.............

Share this post


Link to post
Share on other sites

Update:

Finally got my car back on Thursday - after much investigation this is what I have been advised.

When the original fault with alternator / battery happened I have damaged one of the pumps in the fuel tank. Due to the tanks horseshoe design ( ? ) the pump that drives the fuel over to the other side has ceased to work ( reasons unknown ) which now means I have to ensure I never drop below the half a tank mark or my engine will cease to receive fuel.

I asked for an estimate to fix and to replace the tank ( is the pump part of the tank ? ) and the supply and installation price was over 2000pounds plus vat !?!?!?

Question: Is there an alternative fix to replacing tank and pump? Has anyone had similiar problems and can point me in the right direction?

All help appreciated....

Share this post


Link to post
Share on other sites

I think you are being fed a load of bull! :mad:

there is only one pump in the tank and it feeds petrol to a set of eductors that suck up the petrol in either side of the tank and send it to the fuel rail.

There are 2 accesses to the fuel tank from the boot. All repairs to either side of the fuelsystem can be conducted through these. My Elsawin is not working atm but I'm sure someone can have a look and post the repair process. You don't need a new fuel tank. At worst a new pump assembly, but you may get away with just some components.

HTH

Mike

Share this post


Link to post
Share on other sites

It looks like I need to investigate this further as the info on here definateley contradicts what I have been told by the garage? One for the new year.............

Share this post


Link to post
Share on other sites

your fuel pump WILL die SOON! mine did the same about a week prior to giving out completely...

Sorry to break the news, but order one now, I bought the whole assembly and i changed it in less than 1 hour.

-Richard

Share this post


Link to post
Share on other sites

Sorry for the delay in replying........It has ran fine on petrol and LPG as I haven't yet let it drop below half way on the gauge. I have been tempted to see what happens but as I need the car to do an 80mile round trip everyday Im not prepared to take the risk? Just to update as well, the 120amp Alternator seems to be coping with everything switched on( heated seats, front & rear demist, lights, music etc..) except I get an annoying message from the sat nav that it can't read the disc? I have received details on here for an updated sat nav disc version which I hope santa is bringing but this message wouldnt be connected to the amps query..would it? Not every time I get in the car but when the message arrives and I cancel it, it can trigger again and again....6 times one morning and then ok?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0