Issue after battery wrong connection...

30CSI · Post by **30CSI** » 25 Dec 2019, 11:06

Dear all,
Il have one 850 from 1996, unfortunately the battery polarity was crossed... So the car does not start anymore... I have checked all fuses, all are OK, but no indication on the board panel (all lights are off) I heard the issue could be the ecu? But how I can be sure? Do you know if this car got main or central fuse to protect electronics against wrong polarity battery connection? I really want to repair my car...

Thanks for your help.

Francis

Post by **misha** » 25 Dec 2019, 12:07

No protection from wrong polarity.
What you can do is to check relays under the fuse box cover under the hood....since your intstrument cluster is dead too.

Post by **cn90** » 25 Dec 2019, 16:39

- Search forum, but I believe it is some kind of relay(s), nothing big...

Post by **cn90** » 25 Dec 2019, 16:41

https://volvoforums.com/forum/volvo-s70 ... ity-89619/

Get a J relay on ebay or dealer.

Post by **erikv11** » 26 Dec 2019, 08:16

Yes, what they said: check the three J relays in the fuse box at the driver's window, it is almost always one or more of them has blown. These are cheap and generic and otherwise almost never fail, junkyard is the best source.

Post by **abscate** » 26 Dec 2019, 09:39

Thats probably the diode that protects the circuitry from spikes when the relay opens that blows on reverse polarity, but that should blow a main fuse upstream, failing closed circuit.

Ghosting erik...

Looking at the several 'reversed polarity threads' - almost all are resolved with the J relay(s) replacement, though.

30CSI · Post by **30CSI** » 26 Dec 2019, 15:14

Hi,
Cn, Erik & a abscate, thanks lot for your replies and information, I removed then tests the 3 j relays, all are faulty, it seems the diodes are deads. I replaced the j by straps then all light on the pannel board were on again and I was able to start the engine... So thanks again, I found some damages on the cable to power abs motor pomp, so I have removed and opened the motor, replaced the wires, power on the motor (its working) then put it back to the abs block. I still have abs on on the dash board, may be the abs controller is dead, don't know if I can check his status trough obd socket...
Again, I'm really impressed by the level of technicity of you guys, and the amount of the tech doc available on the site... , here on a local forum nobodies were able to help me except telling me to change ecu or bring my car to the doc, or to the bin...

Thanks.

30CSI · Post by **30CSI** » 26 Dec 2019, 15:17

Thanks to Misha as well

Post by **cn90** » 26 Dec 2019, 15:55

Too bad you live in Toulouse, otherwise I have a whole bunch of J relays in my garage.

Next time I am in Toulouse, I can bring them for you...

À la prochaine!

30CSI · Post by **30CSI** » 27 Dec 2019, 03:05

Thanks cn, so see you in Toulouse next time

I found x3 30 amps relay in my mess to replace the faulty J ones, looks like OK now, just the abs is still not working despite motor cable replacement.
BR
F.