2004 XC90 2.5 AWD - Polarity Reversed

jholden19 · Post by **jholden19** » 06 Feb 2021, 11:20

Hello

XC90 was jump started and polarity reversed for one second. Now the entire electrical system is dead. No interior lights. Nothing when the key is turned. Battery has a full charge. I have checked continuity to fuse boxes and all seems OK. I have checked the relays and they seem to be OK as well. There is continuity to the alternator and ignition module.

Can someone suggest what I should check to determine what has been blown?

Thanks
Jonathan

Post by **ZionXIX** » 06 Feb 2021, 12:58

I would start pulling relays out and check them for function.

Post by **volvolugnut** » 06 Feb 2021, 13:17

Check the similar topic links below for other suggestions. Good luck.
volvolugnut

jholden19 · Post by **jholden19** » 06 Feb 2021, 17:51

Thank you for the replies. Turns out it was the battery. I charged the battery and checked it out under load. All looked fine. Brought it into the shop and it was dead. With a new battery, the interior lights came on and the car started. So far, I have not noticed any damage.

Post by **volvolugnut** » 07 Feb 2021, 08:48

These modern Volvos demand good battery voltage. Cranking speed is a poor indicator of good voltage on these cars, unlike older cars.
volvolugnut

Post by **ZionXIX** » 07 Feb 2021, 11:08

volvolugnut wrote: ↑07 Feb 2021, 08:48 These modern Volvos demand good battery voltage. Cranking speed is a poor indicator of good voltage on these cars, unlike older cars.
volvolugnut

I used to check headlight brightness to determine battery charge