I got the 'Power system service required - Urgent' on my 2005 D5 (UK spec). The garage replaced the alternator. However it produces only about 13.5 Volts most of the time (which triggers the power sustem warning again), but sometimes it goes up to 14.5 Volts, which keeps the car happy. I can't see any obvious poor connections. My question: is the voltage being controlled by the car's management system? Should I try some sort of reset? The battery is only about 6 months old. Grateful for any suggestions.

 

modern alternators, or more correctly modern voltage regulators, do in fact manage the voltage to reduce the parasitic drag from the alternator when its not needed to charge the battery. So you won't see 14.5V all the time. Volvos also have a battery monitor system that can be reset. I suspect when they did the alternator they had to (or should have?) disconnect the battery which may have tripped up the BMS.

Here's a thread that may help https://www.matthewsvolvosite.com/fo...ic.php?t=57856 or check Youtube for reset how to vids.

If the battery monitor reset doesn't solve the issue, then your issue may be related to the replacement part not being exactly correct for your model/year or possibly is related to the voltage regulator. On some Volvos, the regulator can be replaced independent of the alternator. finally, the replacement install may have some minor wiring issues with the connectors etc. So start with the BMS reset procedure then go from there.

 

Many thanks, I will try the BMS reset first.