Battery terminals connected wrong way around!! Now what???

[Stoeprand]

Hi,

Whilst renewing the flat battery on his Tuscan MKI the owner thought it would be easier to start the car with the new battery outside the car first by using jumper cables on the car terminals, to be able to drive the car out of the garage to get easier acces. But he connected the jumper cables the wrong way around to the car battery terminals.... There were a lot of sparks and and it all resulted in the car doing nothing anymore except for the exterior lights and horn.

Both large fuses were checked and renewed. The one for the alternator and the one in the passenger footwel but no result. Only the alternator fuse was blown by the way...

Does anyone have any idea what might be damaged? All other fuses in the fusebox are okay. Does anybody know of any fusible links or so?
When using the ignition switch nothing happens.

Thanks a lot for your help!

[aaron_2000]

As long as he doesn't drive it up to 88 he should be fine.

Seriously though, has it been started up since?

[Stoeprand]

Hi,

Yep, we've connected the new battery correct but still nothing works except for the exterior lights, hazards and horn.

[craigjm]

Fried ECU?

[Boosted LS1]

Crikey, he must have been a very determined bloke. I'd have expected an explosion.

[Chim450]

Fried ECU as said earlier could be the cause, also does the immobiliser disarm? Can you hear the fuel pump prime?

[aaron_2000]

I would expect the ECU is done. I've read about cases where the car gets left for a few minutes then starts back up with no issues, however I've also read about cases where the car ends up burnt out. Probably best to get it in with a specialist.

[lucido grigio]

Alternator might be damaged but that fuse that blew may have prevented this.

[tofts]

It's likely that every control unit in the car is blown.

Most of the units have diode protected outputs to clamp small transient currents, reversing the polarity means there would be a direct path to ground through these diodes and an almost unlimited current flow

There are two main fuses, one by the alternator and one in the passenger footwell behind the carpet As you have checked the fuses, go round and try each of the following systems:

Main engine ECU
Window control units
Alarm/Immob
Heater control
Dashboard
Diode pack in alternator (may have been protected by fuse)
Dashboard
Mirror control unit

There are no wiring diagrams available to the public, but there is a document with all of the pin designations that has been available for some time, with this it is possible to work everything out but it's hard going.

The window modules would be a good place to start as they require no ignition, if they do not work, remove the center console and probe the two thick solid red and solid black for power, if there's 12v here then the units are fried. Just from this, I can tell you almost everything else will also be fried too!

Jody

EDIT: As we have emailed before, I have sent a message with an attachment you will find useful.

Edited by tofts on Saturday 5th August 08:57

[Stoeprand]

Hi, I'm back again....

With good news!
Thanks for everybodies quick reply!

Started work on the car this morning and found the feed to the ignition gone in the fusebox.

Opened up the box and repaired the link. This brought a lot of systems back to life.
Except for the alarm, doors, windows, fuel pump and dash.

Renewed alarm ecu, door ecu's, fuel pump fuse and repaired feed to dash primary print.

All is fine now!!
Better not try wrong polarity at these cars.....

A nice weekend to all of you!!!