What happens when you connect battery terminals wrong

[ian505050]

What happens when you connect battery terminals the wrong way when trying to jump start a car.

The Car is a 2006 1.6 Petrol Focus

1.)Car will not start due to dead battery and the only noise that can be heard is a clicking due to lack of power in the battery.

2.)Someone comes along and tries to jump start the car using jump leads from another car that is running but connects them up the wrong way for 15 seconds causing the cables to heat up.

3.)The car now now shows a red light and the display reads 'engine system fault'

4.) The car now no longer attempts to start (no clicking noise) and will only show the above error message.

What will be damaged? The AA guy says fried ECU or blown a big fuse.

The car still has all its lights on the dash and the displays all work and it recognizes when the bonnet is open or a door is open ect.... but does not make any sort of noise to even attempt to start.

I have taken my car to a local side street mechanic that we know who has a diagnostic machine to check for faults.

My question is on a scale of 1 to 10 how worry should i be and what parts may need replacing? Is the ECU the worst case scenario?


https://i267.photobucket.com/albums/ii302/ian505050/ian505050%203/IMAG3416_zps1e86d78a.jpg

[Slacker24seve...]

[BakesBeans]

The good news is you haven't run out of fuel.
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[ian505050]

The car has half a tank of fuel and all the fuses are all the main 60A and 80A fuses are intact.

[Nexus Icon]

Disconnect the battery completely for 30 mins or so. It might clear the fault. There's a possibility it's only flashed up because of the polarity-irregularity.
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[ThoughtContro...]

Your existing battery is still knackered. At least one or more cells are likely to have gone into a reversed polarity condition and be dead.

Check your existing battery voltage. It might be that the fault indicates because the battery voltage now shows 8V or less (and would likely nosedive further under load since you've damaged the cells of a flat battery).

Replace the battery and check all the fuses you can find as has been stated. If the LCD display still works and the microprocessor controlled system diagnosis still shows some life then at least it's not blown that.
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[Boxing]

Will the person who put the jump leads on the wrong way around be contributing towards the repair bill?

Also in the event of a flat battery, surely if its a manual it'd be a lot easier to just ask someone to give you a push and you can bump it? Drive it for an hour and if the battery is good it should charge up.

[FirebladeRuss]

Battery will almost certainly be fucked now.

I can't see how the ECU would be goosed if the dash is still lighting up as shown in the picture.

Alternator may also have popped due to the jumpstarting the wrong way (how was thsi got wrong!!?? red goes to red, black goes to black....it's not rocket science!) - which may also be what the system is picking up as the problem.
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[Hetzer]

I had Halfords change the battery in a Shogun and the guy shorted it with a spanner, which set the ECU into some kind of fecked mode. It wouldn't idle, stalled if it was attempted. It cost Halfords a bunch of money to have Mitsubishi come with a low-loader and take the car away to be re-programmed.
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[Pete.]

[The Artist]

1. New battery, fully charged.

2. Cross your fingers.

3. Unlikely to be fuses as connecting the battery the wrong way will not cause a current spike.

4. I would like to think modern ECU's can detect reverse polarity but I may be asking too much.

[goto10]

[Clutchy]

As said, disconnect battery for an hour, new battery and then post back results!
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[uberkron]

Hetzer, alot of mitsubishis dont idle after battery change. You just hold the rpms at the idle you would like and go through the gears.

Good work getting it paid for by someone else!
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[uberkron]

Hetzer, alot of mitsubishis dont idle after battery change. You just hold the rpms at the idle you would like and go through the gears.

Good work getting it paid for by someone else!
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[Nb]

On a scale of 1 to 10 id be worried at about 9. Depends how lucky you are, dashboard module might be fooked or the engine control unit or it may just be a fuse somewhere. There's lots of hidden fuses on the focus. Get it plugged into a decent diagnostic machine ideally Fords ids and the problem will show up.
These cars have whats called a smart charge system where the alternator is controlled by the ecu directly so you can see the potential for damage....I hope it isnt too badly damaged.
We had one bloke put a jump pack the wrong way on a punto and it blew the ecu which cost 800 pounds to replace.
Fingers crossed for your focus!
The focus nornally gives a clue as to a poor battery, your model normally flashes the dipped beam lights and the dash flickers when the battery voltage goes low.
.
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[Sako]

Do you own a pushbike or decent walking shoes?

...if not, then it may be time to invest in them.

[FirebladeRuss]

Honestly, my money is on the battery being definetly goosed first and foremost, with the diode/rectifiers on the alternator likely to be damaged a close second.

There's always a risk it may be the ECU, but that is worst case. It's a bit like asking online why your car has a bit of white goo on the oil filler cap even though the car runs fine. 90% of people will be telling you the head gasket's gone, whereas often it's a simple as the car only does 2 mile journeys and it's condensation build up.

Start with trying cheap/free options first.

Spurious dash messages like "engine systems fault" could mean anything, not specifically that the ECU is cooked.

https://www.fordownersclub.com/forums/topic/33911-2006-focus-engine-system-fault/

First step is to borrow a working battery and see what the car does.

I'm suprised the battery didn't do something spectacular when connected the wrong way, as they often do.
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[Hetzer]

[Nb]

Any update as to what if anything went pop?
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Colin1 wrote 'Im grateful for what i can get, which isnt all that much.'
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[treeno]

[crazy Legs]

[EazyDuz]

The moral of the story is, don't get Carvel to jump start your car.
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