# Flat battery - alternator NOW WITH PICS



## steve o (Dec 5, 2006)

Hi chaps,

as per title, got a flat battery. A jump start and quick voltage check on the battery revealed no voltage coming back from the alternator. You usually see somewhere around 14vdc with the alternator running, but all I got was the 12v from the battery which slowly kept dropping and dropping until the car died.

So, either there's a connection problem or the alternator is goosed! Anyone got any common faults on the alternator, have any suggestions or a how to on how to take it off etc?

Belt looks ok and the alternator is driving, so deffo not that.

Any advice welcome.

Cheers.
Steve.


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## was (Mar 24, 2003)

sounds like your voltage regulator has packed up,

this link might help : viewtopic.php?f=2&t=138963


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## steve o (Dec 5, 2006)

Sorry for the delayed response, been away on holiday for 2 weeks!

Do you really think its just the voltage regulator? I don't get any voltage increase from the alternator at all once its running. All I get is about 12.5v when switched off, it will fire up, but then the voltage just slowly gets lower and lower until the dash board lights up like a christmas tree and the car fails.

I don't want to split apart the alternator to replace the regualtor, put it all together again to find the alternator was knackered! Are there any tests I can do to definitively decide which part is at fault.

Cheers,
Steve.


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## Bikerz (Aug 23, 2008)

Is the battery toped up with de-iornised water?


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## mark_hogan (Jan 8, 2009)

Have you checked the connections on the back of the alternator to see if there is any voltage there??? if there is you might need to check if the cable from the alternator to the battery is in tact. if all of these things are ok then check the voltage regulator...

Hope this is of some use 

Mark.


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## steve o (Dec 5, 2006)

I haven't checked the connections on the alternator itself yet. Are they easy to get to? It looks very snug in there!!!

But lets say I do check and voltage is still reacting the same way? Does this point to the alternator or the regulator?

As for battery water, the battery is only 2 years old and I've never topped it up. The level looks ok.

Cheers.
Steve.


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## Bikerz (Aug 23, 2008)

Batterys can loose fluid within weeks of being new and means they wont hold a charge at all well, worth looking and making sure its upto the mark. AGE has NOTHING to do with it


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## was (Mar 24, 2003)

steve o said:


> I don't want to split apart the alternator to replace the regualtor, put it all together again to find the alternator was knackered! Are there any tests I can do to definitively decide which part is at fault.


changing the voltage regulator is like a walk in the park compared to changing the whole alternator .


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## steve o (Dec 5, 2006)

Just double checked the battery and water levels are fine.

I'm confident its something to dow it the alternator, cables or regulator as I don't get any rise in battery voltage when the engine is running.

Just double checke the voltage on the 20C control panel diagnostics and after being sat on the drive for 2 weeks the display was reading 11.8v, the car still turned over, momentarily dropping the voltage to 10.5 while it turned over, then returning to 11.5v.

Again, I'd expect to see 13.5 to 14v coming from the alternator but I get nothing. The voltage is stable at 11.5 and just slowly drops off as the car consumes the power. It definately not getting topped up by the alternator, but the question is, is it the alternator, or just the regulator?

Steve.


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## was (Mar 24, 2003)

An altherator is basically a huge coil winding and a bridge rectifier (voltage regulator) The coil windings very rarely fail. The voltage regulator does all of the work, it contains the bushes and control circuitry.

my money would be on a faulty regulator.


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## mark_hogan (Jan 8, 2009)

was said:


> An altherator is basically a huge coil winding and a bridge rectifier (voltage regulator) The coil windings very rarely fail. The voltage regulator does all of the work, it contains the bushes and control circuitry.
> 
> my money would be on a faulty regulator.


It does seem to be this with what has been explained.. the same whent on mine but as I dont have the experties in changing one of these I got a reconditiond alternator and fitted that. was'nt too expensive £99.

Unless you can change the regulator or have gat a how to you might find a reconditioned alternator the easy option.


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## steve o (Dec 5, 2006)

I can't find a "how to" on changing the regulator. Does anyone know what I need to do in order to change it?

Hope someone can help.

Cheers.
Steve.


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## John-H (Jul 13, 2005)

Don't forget to check the integrity of the fuse links on the tip up pannel on top of the battery - one of them is for the alternator output.


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## steve o (Dec 5, 2006)

Oh ok? Didn't know about that. Do you know which one? Gonna have a play now.


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## John-H (Jul 13, 2005)

These are the safety fuses that take all the output from the battery bar the starter current and the one on the left is the alternator link.










Take the cover off and give everything a wiggle and a prod. With luck it's only one of the nuts come loose. Check for discolouration of the crimp connection and for signs of melted wire insulation - the loose connection (if it is this) has likely been getting hot. Check the link has not oxidised away too.


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## steve o (Dec 5, 2006)

Gutted mate, checked it all out and its ok.

Removed some of the covers above the alternator and managed to get to the terminals on the bridge rectifier (Voltage regulator) and there's nothing coming directly out of that, so deffo something to do with the alternator!

Just been struggling like buggery to get the regulator off. Managed to get 3 bolts off, but stuggling to get the phillips screws out. There appears to be a cover over the rectifier. I've managed to get the top 2 nuts off (which held the +ve wire on and the earth nut) and managed to get the nut off at the bottom which holds the cable in place, but there's also a phillips screw holding the cover on as well and I just can't get in! AAARRRGGGHHH!

Give up for the night now. And to add more chaos, I managed to snap the yellow dip stick tube in the process as I tried to wedge my big fat hands down the small gap!!! So thats another job I need to sort once I've done this!

Does anyone know how to get the voltage regulator off??? There must be an easier way?

Also, how hard is it to replace the yellow dip stick tube? Currently have tape over it to stop any shit getting down there!

Absolutely miffed off!

Steve.


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## was (Mar 24, 2003)

a tool like this is very handy for removing the regulator. The screw at the bottom of the regulator is usually hidden by some pipework. Just push the pipes to one side while removing the screw.










the regulator looks very similar like this :


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## steve o (Dec 5, 2006)

Ok, maanged to get it out after much swearing and knuckle scraping!!!

Just need to order my replacement (audi couldn't tell me whether mine was Bosch or Valeo - its a bosch!) its £30 ish part exchange from audi, so will get that ordered tomorrow!

Also need to repair the dip stick tube now cos I snapped it clean off!!! Anyone know how to remove the bit that is still attached to the sump?

Cheers for the help guys! Fingers crossed thats the problem and I don't need to replace the whole alternator!!!

Steve.


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## tufty (Feb 3, 2008)

steve o said:


> Ok, maanged to get it out after much swearing and knuckle scraping!!!
> 
> Just need to order my replacement (audi couldn't tell me whether mine was Bosch or Valeo - its a bosch!) its £30 ish part exchange from audi, so will get that ordered tomorrow!
> 
> ...


Hi dip stick tube can be a pig to get off, best is to plug the hole with a rag and snap it off with pliers. New dip stick is £3.16 Part no p A06A 103 663 B

Mark


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## EnfieldTT (Jun 7, 2008)

Steve mate, I hope it's only the regulator. You'd be amazed how much that little - relatively inexpensive - part can cause havoc with your electrics.

Reading back your thread sounded like I'd written it myself! I too couldn't get one bolt off, chored my knuckles up, snapped the ywllow pipe - and eventually raised the white flag :lol:

BUT...in the end, it _was_ only a faulty voltage regulator for me 8)


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## steve o (Dec 5, 2006)

lol!!!

Can't believe you snapped the yellow dip stick tube as well!!! How did you go about changing it? Did you just destroy it as well?

How does the new one fit on? Is it push fit or does it screw on or something?

Steve.


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## tufty (Feb 3, 2008)

steve o said:


> lol!!!
> 
> Can't believe you snapped the yellow dip stick tube as well!!! How did you go about changing it? Did you just destroy it as well?
> 
> ...


 It was brittle so just fell to pieces using the pliers, the new one just pushes on and clicks in place, make sure you have it the right way round

Mark :wink:


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## steve o (Dec 5, 2006)

Nice one Mark.

And cheers to everyone who helped me! Might do a little "how to" when I put it all back together! Them bolts can be a right arse not knowing which ones you need to take out!
Steve.


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## John-H (Jul 13, 2005)

Did someone say How To?  - Perhaps you might like it to feature in absoluTTe magazine too?

viewtopic.php?f=1&t=141652&p=1458008#p1458008


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## steve o (Dec 5, 2006)

Now then, another quick question before I pack up for the night.

When I went to audi last week, they told me the voltage regulator could be one of 2 part numbers depending if I had a Bosch or Valeo unit. The part numbers they gave me as possibilities were :

Bosch - 038 903 803
Valeo - 06B 903 803









Now then, the number on my regulator is none of those. I assume I need the two parts of the regulator (see pic) as both items appear to have electronics in them.









one has the number 028 903 028 and the other has the number F00M 145 225. Can anyone confirm the part numbers and what exactly I need?

















Part number for the dip stick tube appears to be 06A 103 663 B as Mark said (see pic) 

















Should I get a new dip stick as well? Can't see a number on that. Does anyone know what it is?

Cheers again.
Steve.


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## bobbobb (Dec 24, 2008)

just give audi them part numbers you might find they have been replaced with a newer part number they will tell you

its happened to me a few times while repairing mine


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## was (Mar 24, 2003)

the left part is the regulator, the right part is just a cover.


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## John-H (Jul 13, 2005)

06A 103 663 B - Guide funnel @ ~£3.19

Alternator 028 908 028 E has been superceded by 038 903 018 QX for which the regulator is 038 903 803 EX @ £39.34 or there abouts. Both units are Bosch 120A units as far as I can see - but get the dealer to confirm as any mistakes will be their responsibility :wink: .


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## steve o (Dec 5, 2006)

Cheers John,

gave them the chassis number and they didn't ask any other questions about part numbers so assume I'll get the right one!

All in for the regulator, dip stick and dip stick guide was less than £40! So can't complain! Just hope it does the trick!

Cheers again.
Steve.


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## keetz (Jun 24, 2009)

Hey guys, I'm having the same problem here. Battery reads about 12.5v then drops to 12 with engine running, then slowly drops after that. I'm about to change the regulator. Does the cover have to come off? If so how many bolts/nuts/screws in total?


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## keetz (Jun 24, 2009)

Never mind that last post. I got the thing off. Tricky though. And guess what? I broke the dipstick tube too! That thing must have been really brittle because it snapped with hardly any pressure. Maybe the heat had got to it! Now I just have to find the part. The part number is the same, F 00M 145 225. Is this replaced with 038 903 803E?


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## stevebeechTA (May 16, 2009)

I have had a battery prob yesterday, Took it to derby audi and they wanted to keep it and charge before they tested it  so they could do a proper test to ascertain wether its the battery or alternator, although the i needed the car so i just got a new battry. hope that is all it is after reading this. Battery fluid levels were low so i presume it was knackered.

Got to give audi there due's though, they weren't going to charge me for the test, and they did think it was unlikely that it would be the alternator at fault.


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## steve o (Dec 5, 2006)

Its pretty simple to see if its your alternator or not. Bang a multimeter (test leads) on the battery. It should be about 12.5v when switched off, then anything between 13.5 and 14.5v when running. If the voltage doesn't go up when running, you have an alernator issue (cables, connections, alternator, voltage regulator etc...)

If you don't have test leads, you can see the voltage by using the climate control display. Press the recirc and up arrows together to enter the options. Use the temp dial to scroll up to option 20C, then press recirc again to see the information. This will display the voltage.

Keetz, you've got the same item as me. I just gave audi my chassis number and they sorted me no problem, hopefully parts will be in stock for me to pick up on my way home today.

Steve.


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## steve o (Dec 5, 2006)

Ok guys! I'm absolutely delighted! Swapped the voltage regulator today and the running voltage is back up to 14v!!! Sorted :lol:

Just one question. Will the car have gone into any kind of safe / limp mode when the battery cut out and all the lights on the dash started lighting up like a christmas tree?

I haven't had chance to drive the car yet as I still need to fix the dip stick tube (I'll do that tomorrow), but as I don't have Vagcom, just wanted to get peoples thoughts on if everything should now be ok?

What do you recon? Do I need to somehow reset things? Or does the battery being off for a few days reset any errors anyway?

Cheers.
Steve.


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## John-H (Jul 13, 2005)

Well done Sir! 

You should be OK. If you want to reset everything, which may be a good idea if you've had a flat battery; as sometimes corruptions can get stored in memory, then disconnect the battery for a minute or two. Then perform a clean connect - one firm clean connection of the battery lead (as opposed to bouncing it on and off making sparks!) making sure it stays connected whilst you tighten it up. Make sure you have your radio code before disconnecting and reset the windows once connected.

You will presumably have some error codes stored but this won't do any harm - just delete them if you get a chance to use Vag-Com before you forget and later think you've got a fault.


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## redsi72 (Nov 13, 2006)

Mines gone too :evil: . Just as I pulled upto the garage for its mot, the red battery dash light comes on. Its a mate who did the mot and he struggled to pass it because of the emissions being up (car not running right, hunting all the time)
Its amazing how little distance/time you have, only driving on a charged battery draining as you go. I dropped the window an inch and headed home. Its a brand new battery, had 12v in at the start which lasted three miles before the mother of all battery dash lights comes on(big orange picture of a battery) thirty seconds later the car cuts out.Thanks for the warning audi, would never have known a fault existed :roll: 
Car is on a 2001 plate and covered 60k.
Guess what I will doing later 

Si


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## stevebeechTA (May 16, 2009)

Thanks for the tip Steve, i have just been out and had a butchers at my voltage using the air con, car of it was showing 12/12.5 cant remember exactly, then engine running 13.8 / 13.9 . so i presume all is ok.

cheers steve [smiley=thumbsup.gif]


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## stevebeechTA (May 16, 2009)

In case anyone needs a battery Costco has Bosch Silver's at a decent price

I found them to be the cheapest place for a decent make battery, the last time i brought a battery was for my merc (bosch silver) for £75 quid or somthing at cost co instead of £120 from other place's for the same battery.

My tt one cost £49 again for a bosch silver, did not bother looking around as i did not have time. I presume they are still competitive.


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## snappy (Apr 29, 2009)

i've got the same prob steve o, lets just hope mine is the regulator also!!
great write up and all the contributions, helped me out could save me a bundle!


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## S&amp;S (Mar 29, 2009)

guys any confirmation on the new part number, mines is a bosch F00M 145 225, im assuming that 038 903 803 E is correc t?


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## DVD225 (Oct 15, 2007)

This seems to be a common fault!!! wish Id found this post when I did a search. Luckily the forum guys came to my help. Replaced the whole alternator so TPS got a good 1 back that only requires a regulator (good business).
So should we add this to the list of dash pod, coil packs, Arb & wishbone bushes alarm siren etc etc.
What would we do without the forum :roll:


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## dankay1989 (Mar 23, 2010)

thanks for the help on here, will be using this info tonight


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## Hobsini (Apr 26, 2011)

Ok, have the same problem and really struggling to get that bottom phillips screw off. Can anyone help? Should I remove the pipe to the right?


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## Hobsini (Apr 26, 2011)

Several people appear to have fixed this themselves. What did you use to remove the bottom Phillips screw?


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## danchiefton (Nov 19, 2012)

As I am on the process of replacing my regulator I found this vid on you tube. Its very helpful and explains a lot





.

I dunno if that works but basically I did a search for audi voltage regulator and its the top one with the Irish mechanic


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## John-H (Jul 13, 2005)

That is to be sure. Oil add it to the Knowledge base. Thanks


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## scoobzIII (May 25, 2014)

Hi guys,

I'm still running my TT that I bought in 04 

Very few miles so it's lasted a while, I went on holiday for a couple of weeks and it was a bit sluggish to start so I thought she needs a run to charge back up. I didn't get round to doing that and there were a few short trips which probably drained the battery further.

So today I got the yellow battery warning and was just going to go for a drive but I needed fuel first.... Well that was it, turned the key, nothing.

RAC came out and jump started the car, he said I was getting no voltage from the alternator and it would need to be replaced so I jumped on here when I got back and found this ancient thread 

I did the 20C test and it was 11v before startup, 13.3 (jumped around a lot) whilst idling and driving, that's a good sign right? I'm hoping the battery just needs a good charge.

Any feedback would be good as I'm stressing out here, thanks!


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## John-H (Jul 13, 2005)

You can get a slightly lower voltage at the climate control than actually appears at the battery terminals depending on the loss and state of various connections.

Basically, if the alternator is working you should get near 14V at the battery depending on temperature. The reading should be pretty steady and change only perhaps 0.2 0.3 of a volt or so with engine speed and load.

If the battery voltage is going to 12V or so intermittently whilst the engine is running it's a sign of a failing alternator or a bad connection. This may be what the RAC spotted. If it's the alternator you can change just the regulator part cheaply.

If the alternator is fine it could just be that the battery needs charging. It could also be that the battery is old and effectively low capacity, so the standby drain of a couple of weeks is enough to kill it.

There are various tests you can perform on your battery to ascertain whether it's holding charge. Once fully charged (make sure!) you can do things such as turning on your main and dip beam for an hour and then try starting it.

With HID 35W dips and 55W mains you'll have a 15A draw and an 80 Amp.hour battery should fully drain in over 5 hours (80/15). If your battery is old and down to 20% capacity it will probably not start after the hour. If you have a multimeter you can run a more subtle test by measuring the battery terminal voltage after 15 minutes of drain and then no load rest, and look up remaining charge and work out capacity without running flat in the effort (see table in link).

There is also the possibility you may have excess standby drain but check the obvious and most likely first.

See this post for some useful information:

viewtopic.php?f=2&t=188365


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## Hoggy (May 8, 2002)

Hi, It appears alternator is charging & battery just requires a 12 hour charge at least to get it back to any where near fully charged. Charging volts will be lower as battery is flat & alternator is supplying max amps, charging volts will rise as battery capacity increases.
Hoggy.


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## scoobzIII (May 25, 2014)

Thank you both for the feedback, very much appreciated.

I've got a trickle charger so I'll get that on and recheck readings when it's topped up. RAC guy said there was nothing coming from the alternator, maybe he was checking the wrong post? He charged the battery for an hour to make sure I got home (3 miles). The car happily started again an hour or so later when I made this post.

Thanks again.


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## John-H (Jul 13, 2005)

Intermittent faults are one of the worst influences to a correct diagnosis. Perhaps the RAC guy made a mistake but perhaps he correctly reported the fault during a moment of its clear evidence.

Keep monitoring the 20C - if it keeps dropping to 12V or less when driving it's either your alternator or a bad connection causing problems. Jumping up and down is clearly a fault. If it stays steady at near 14V but you still get starting issues it's likely your battery.

Your alternator should be capable of supplying 120A so it won't take long from flat to get to 14V. An old low capacity battery (20AH?) will get there quicker than a flat good battery (80AH).










Just for indication - if the current limit is hit the voltage will be low but rise as charge increases. As soon as 14V is reached the current will start to fall.


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## scoobzIII (May 25, 2014)

Thanks for the info John, it only jumps around within a 0.3v range mostly.

After a 5 hour charge the battery read 14v which jumped down to 13.6 with the engine running. The revs seem to make little difference to this reading (20c reading).

Had a voltmeter on it today and the alternator is kicking out a solid 13.5 at idle. I know that's the lowest end of acceptable but it's an old car that doesn't get a lot of mileage (sometimes only gets a run once a week)


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## Hoggy (May 8, 2002)

Hi, Charging volts seem fine to me.
Hoggy.


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## scoobzIII (May 25, 2014)

Hoggy said:


> Hi, Charging volts seem fine to me.
> Hoggy.


Thanks Hoggy


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