C70 Diesel Slow Starting

Terminal 30 issues on Volvos can be tricky. An interrupted terminal 30 can definitely cause starting problems. Have you checked the battery voltage when the car is off, and also while you're trying to start it? A significant voltage drop during cranking could point to a failing battery. Also, have you had the battery tested recently? These modern cars are very sensitive to voltage issues.

Thanks for the quick reply! I haven't properly tested the voltage during cranking, just after it's been sitting. I see what you mean about voltage drop. Where's the best place to start looking for potential causes? Is there a common circuit breaker or fuse box location that's usually the culprit for power supply issues?

Okay, so if the voltage is normal when sitting but drops significantly when cranking, it does sound like the battery is the main suspect. While it could be a wiring issue or a bad connection somewhere, a dying battery under load is far more common. Honestly, diagnosing terminal 30 faults can be complex and require specialized tools. I'd suggest getting the battery professionally load tested and, if that checks out okay, then consider taking it to a trusted workshop to check for any parasitic drain. It sounds to me like you might be best off letting a professional diagnose it, based on your description, since finding a wiring problem is difficult without the right gear.

Appreciate the advice. I took your suggestion and had the battery load tested – it was indeed heavily discharged and failing. Replaced it for around 290€ and the car starts perfectly now. Thanks again for pointing me in the right direction!