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Morning, we've a 2011 T5 campervan, 72K miles, cared for by previous owners and us. Yesterday, battery light came on, then off, then on, then off. Today it's on pretty solidly.
The battery is 1 year old. Charged it overnight and it's sitting at 12.8V. The leisure battery that's hooked up to the alternator is also at 13V. With the engine idling, I was getting a bit of fluctuation but typically 12.5V - 13.2V. Hovering at the lower end more.
Have:
- checked the alternator fuse and clean and good
- battery ground wire clean and good continuity
- battery terminals clean and tight
- fuse compartment under the battery is clean and dry, nothing untoward looking
I crawled under the van but can't find the wiring from the alternator to check current when running ... is it obvious?
So guessing the alternator is goosed?
Any other things to check for before I phone a garage? And what sort of bill is likely? Bit fed up as having a bad run of things breaking!
Alt should be 14v when running. Or it was on my t5
I think we replaced the alternator at around 100k miles on ours. I can't remember the cost though but it was around the same time as needing a new turbo so an expensive year.
A few years ago a new alternator for my T5 cost £250 at the local McConnechys.
Replacing the alternator on my T5 cost a **** ton. On the 2.5 engine it’s a massive job that requires the whole front end taken off to get to.
Yikes, we've the 2.0 model. I don't mind having a go at spannering, but it looks pretty enclosed and without access underneath, would guess it'd be a nightmare to do
The voltages you are reading presumably at the battery + terminal are definitely too low to fully charge a 12v lead acid battery. Above idle your alternator should be providing >14v Anything causing a voltage drop in the circuit as well as the alternator being gubbed could be to blame. Before condemning the alty I'd check the output at the alternator with the engine above idle.
Theres a 100Amp fuse (Bolt In) underneath the Battery Tray, you have to remove the battery and the tray. AA found it for me on my T5 after a garage shorted the alternator and blew the fuse. At the time in 2009 it was the first one they had ever seen and updated the database for their breakdown patrols. I'd look there first.
Battery appears okay, so:
Fuse?
Drive belt?
Damaged wiring?
OBD2 reader?
AA, RAC or similar?
Battery appears okay, so:
Fuse?
Drive belt?
Damaged wiring?
OBD2 reader?
AA, RAC or similar?
Voltmeter would be my first option. This will give you the information required to diagnose the fault.
Measure alternator output directly. If good, then you need to check the condition of the wiring and connections up to the battery. This can be done using your voltmeter. Any voltage drop above 0.1-2V measured between alternator & battery requires looking at. You need to carry out the same checks on the engine earth lead & battery negative lead. These have to be carried out with the engine running.
Low output measured directly at the alternator & I'd say you've found the culprit. However, the fly in the ointment is that stop - start equipped vehicles have a "smart" charging system. (VW T6 for example) This requires the BMS to "know" the condition of the battery. IE when fitting a new battery you have to input the information via VCDS/laptop. Have you fitted a new battery recently?
And what sort of bill is likely?
They've gone up loads lately
Mk6 Transit in 2017 was £200ish, MK7 Transit last month was £423 at local independents with new belts etc.
They died at 110k and 105k respectively, 72k seems quite low in comparison
I don't know how comparable the prices are to VWs
Thanks all. Fuse is good. Belts look clean, moving smoothly and quietly so guess OK?
Now getting 12.5V at battery with engine running, both at idle and high revs.
I can't see where the wiring is from the alternator to measure current there. Am I being a numpty!
I was being a numpty!
So with the engine running, the meter reading at the alternator is 12.3V, and exactly the same when I move to read at the battery. So assume that means the alternator is not kicking out any/enough voltage?
So next test (once the rain stops) is to disconnect the plug to the alternator with 2 thin wires, a white and blue wire, and test, with the ignition on, but engine not running, to see if one of them is live? If
- it is live, then the alternator has failed
- it is not live, trace the break in the wire and all might be well
Am I right?
Sounds like a duff alternator. Any AA/RAC cover - let battery go flat, call them out to check ?
Had one fail on an Aygo recently. Still charging at 14v plus, but once off, there was a drain on the battery. Traced a 'hum' to the alternator and it was also warm - a diode had failed which stops the flow of power back into the alternator (turns in into a motor). Aygo's are dirt cheap though ! £130 for new alternator, no exchange needed.
was being a numpty!
So with the engine running, the meter reading at the alternator is 12.3V, and exactly the same when I move to read at the battery. So assume that means the alternator is not kicking out any/enough voltage?
So next test (once the rain stops) is to disconnect the plug to the alternator with 2 thin wires, a white and blue wire, and test, with the ignition on, but engine not running, to see if one of them is live? If
– it is live, then the alternator has failed
– it is not live, trace the break in the wire and all might be wellAm I right?
One of those thin wires supplies battery voltage to the alternator to excite the coils. So yes, one of those wires needs to go live when you turn on the ignition. If this is the case I'd suspect that the alternator has bit the dust.
You could try a rectify pack if its swapable but I'd just swap the alternator