Alternator or Battery??

R

Ricardo1992

Member
 Inverurie, Aberdeenshire
Finally the time has come. z4 is now back on the road...almost! Put it in for an MOT at the weekend which it required a little work. Once I finally got the car back, I noticed that the battery light was on. This was not the issue when I dropped off the car. So I took it back to the garage and they told me to just run it and the battery will top up. Which I did....until it broke down 2 miles down the road.

Test I have done:

- Checked voltage with car running and not running. It was both reading 11.6V(ish). My understanding is that this should go to 14.7V when the engine is on. Which makes me think its the alternator.

- I had the battery on trickle charge overnight which I then tried to run the car off of the following morning. It worked! However when driving home, the battery light showed up again. And as I was in front of my house, the car cut out. The battery was on charge for approx. 16 hours.

- Checked the belt and looked fine! So that was eliminated from the equation.

I have taken the alternator out which I believe is the issue. Is there any way of testing it whilst out of the car?
 
If the battery has gone flat then replace it regardless, does sound like the alternator has gone which was the cause of the flat battery. Did you test the output of the alternator at the alternator itself?
 
Scooba_Steve said:
If the battery has gone flat then replace it regardless, does sound like the alternator has gone which was the cause of the flat battery. Did you test the output of the alternator at the alternator itself?
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Was thinking the same. Although there is a measurement on the battery (Green is charged, black it needs charged and yellows its f****d). Currently sitting on black which is understandable. I tested the alternator only at the battery.

There was no noise coming from the alternator so I don't think it will be the bearings within. I'm hoping it will be a cheap fix however I want to know which part of the alternator has gone. But first need to test it... :?
 
Forgot to add, once I got a jump start, the car gave up after 2-3 minutes without moving it. The lights on the dash also appeared one by one until it was lit up like a chirstmas tree before it eventually gave up. PAS was first to go. Unfortunately this was as I was turning a corner... :driving: :(
 
Ok so you tested the alternator at the battery and got 11.6 volts so you need an alternator, change that first, and see how it goes if you have more trouble you might need the battery also !
 
Hi Ricardo
Just read this post with interest as exactly the same thing has happened to our car this week. I haven't been able to test the voltage yet but will be tonight.
My question though is, how easy is it to remove the alternator and whats involved because if it is a relatively simple job that I can do, then I can obviously save myself a few quid.

Thanks.
 
MerBrook said:
Hi Ricardo
Just read this post with interest as exactly the same thing has happened to our car this week. I haven't been able to test the voltage yet but will be tonight.
My question though is, how easy is it to remove the alternator and whats involved because if it is a relatively simple job that I can do, then I can obviously save myself a few quid.

Thanks.
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It's a very simple task. Doesn't take too long. Two bolts to remove the air filter box and you can access all the 16mm bolts from there. However, I recommend you loosen the bolts with a ratchet then use a spanner to take them out...The bolts are very long and there is very little room to pull them out once the threads have cleared. :thumbsup:
 
fixit man said:
Ok so you tested the alternator at the battery and got 11.6 volts so you need an alternator, change that first, and see how it goes if you have more trouble you might need the battery also !
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Was wanting to make sure there wasn't any further checks I've missed which may indicate otherwise...don't want to fork out £360 for a BOSH alternator to find out it was the battery (or if anyone knows anything which may be worth checking)! However contacted Euro Car Parts where they will check the battery for me and if its not that, then new alternator it is...

A bit off topic but has anyone tried RTX alternators? Chatting to the guy on the phone who informed me these are BOSH refurbished alternators (which are branded as RTX for obvious reasons). If so are they reliable? the cost difference is quite substantial however doesn't come with a 3 year warranty but only one instead.
 
Using a Multimeter you can check the Rotor and Stator windings for either open circuit or high resistance. This will be a quick and easy test to do. You will need to split the Alternator to get the regulator/rectifier out then use the terminals to continuity test the stator (housing) and check between the 2 split rings on the comutator. If its one or the other you can get a rewind for about £150. Google Bosch Alternator tests and there are plenty of how to...
 
scotty597 said:
Using a Multimeter you can check the Rotor and Stator windings for either open circuit or high resistance. This will be a quick and easy test to do. You will need to split the Alternator to get the regulator/rectifier out then use the terminals to continuity test the stator (housing) and check between the 2 split rings on the comutator. If its one or the other you can get a rewind for about £150. Google Bosch Alternator tests and there are plenty of how to...
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Thank you! This is the sort of answer I was after!! :cheers:
 
took the alternator apart tonight where I removed the alternator voltage regulator. Turned out that the issue was within this component. The wire within the regulator was broken. A cheap £35 fix compared to the cost of a new Alternator. Ordered a new alternator voltage regulator which seems like the closest place to deliver to the UK is Luxembourg! 2 weeks max before the zed is on the road....
 
Ricardo1992 said:
Forgot to add, once I got a jump start, the car gave up after 2-3 minutes without moving it. The lights on the dash also appeared one by one until it was lit up like a chirstmas tree before it eventually gave up. PAS was first to go. Unfortunately this was as I was turning a corner... :driving: :(
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This is exactly what I am going through at the moment (https://z4-forum.com/forum/viewtopic.php?f=3&t=126843).
 
davidmudley12 said:
Ricardo1992 said:
Forgot to add, once I got a jump start, the car gave up after 2-3 minutes without moving it. The lights on the dash also appeared one by one until it was lit up like a chirstmas tree before it eventually gave up. PAS was first to go. Unfortunately this was as I was turning a corner... :driving: :(
Click to expand...
This is exactly what I am going through at the moment (https://z4-forum.com/forum/viewtopic.php?f=3&t=126843).
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Good luck! Hopefully the experience I wrote about will help you out. One thing to note, BMW refused to sell me direct the alternator voltage regulator however do supply garages with this part. If it is the regulator...in the first instance!
 
Good parts source is ebay for alternator regulators, keep meaning to get one for the Z3 for the duff one I have in the garage, put a recon alternator on when it was only putting 12v out kept the duff one in the garage intending to replace the regulator as bearings are still good.
 
colb said:
Good parts source is ebay for alternator regulators, keep meaning to get one for the Z3 for the duff one I have in the garage, put a recon alternator on when it was only putting 12v out kept the duff one in the garage intending to replace the regulator as bearings are still good.
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I'm thinking of doing the same things, buy a new alternator and then take the old one out and repair it in my own time before selling the fixed alternator.
 
davidmudley12 said:
colb said:
Good parts source is ebay for alternator regulators, keep meaning to get one for the Z3 for the duff one I have in the garage, put a recon alternator on when it was only putting 12v out kept the duff one in the garage intending to replace the regulator as bearings are still good.
Click to expand...
I'm thinking of doing the same things, buy a new alternator and then take the old one out and repair it in my own time before selling the fixed alternator.
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Try a new Regulator first off, you can remove it with the alternator still on the car. I payed about £25 off ebay and it sorted my issue
 
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