V60 D3 multiple system faults, power issue?

[rbcohen]

Hi!

Having some weird issues with a Volvo V60 D3 2011, tried a few things and looking for any advice. If issue gets resolved hopefully this will help someone else too.

Original issue was with the alternator, driving along a charging failure light popped up on the dash - followed quickly by lots of other system failures (power steering, dstc, city safety, etc). AA confirmed and took me to my mechanic, who replaced the alternator (not OEM, but presumably fine). Battery seemed to be OK after a charge, so didn't replace battery.

Drove car to work and back (20 min each way) for a week after the alternator was replaced without issue. Figured car was back to normal.

Driving to Manchester at the weekend, 160 miles in to trip and in torrential rain, all the system failure messages pop up and car enters limp mode. AA turn up and check fault codes, only fault code is "about the alternator". The fault code is reset, incase my mechanic forgot, and the AA escort me the rest of the way without issue.

Car sits in NCP carpark for 2 days, and I drive the 250 miles home without a problem. Drive to work the next day (20 miles) without a problem, but when I try to start the car that evening all the system messages pop up again. Seems to be enough power for everything, although interestingly the boot wouldn't open until I turned ignition off.

Plug in a OBD2 adapter, and the only fault code is U0001. Resetting the fault code, the car will start and seems to idle fine. Leave car off for a few hours, but when turning it back on U0001 and all the service lights are back. Voltage from battery with everything off is 12.4v (a little low?) after charging it with a battery charger and trying to read the error codes for 20 minutes.

So, what should I try next? I've got a replacement battery on the way, as it looks like U0001 can be triggered by low voltage. Not sure the fault should have triggered while driving along the motorway if its the battery though? I suppose I did have lights, wipers, AC, etc etc on.

If the new battery doesn't solve it, has anyone had similar symptoms or got any ideas of what to try next? My only other hunches are that 1) the new alternator is faulty, 2) the two times things have failed, its been raining pretty hard, so maybe water ingress somewhere?

Many thanks for reading, apologies for the long story!