battery hooked up backwards
 

i made the mistake of hooking the battery up backwards one dark night, woops. Most dash fuctions ,starting,etc are not working with a good battery hooked up correctly.Does anyone know how I fix the problem? Is there a major fuse blown ? Would appreciate any help, Thank You . Jariin,The Vehicle is a 1993 XJ6.

Interesting question, without an obvious answer that comes to mind. It's quite possible you did some extensive damage, the first item could be the security ECU which disables the starter circuit.

I'd get a wiring diagram, a test light, and start finding out what is getting power and what isn't.

Good to see you JTO, it's been a while. LOL

I always thought that batt posts are different diameters with the -ve being smaller. So not possible to hook up backwards.

Must be different in the US, you learn something new every day.

Something will surely be fried, and testing everything is the only option.

BTW jasont, welcome to the forum.

Merci, Monsieur Richard

Thanks guys.

I had this happen once to a VW, only damage was fried diodes in the bosch alternator, but I would start with all the fuses.....

You now have a thankless task tracing all the damage done by a battery polarity reversal. The connectors don't have to be fastened down, only touched onto the posts for the damage to be done in milliseconds. You'll have to test every fuse as a first step.
Areas such as microprocessors and alternator diodes going deadshort spring to mind immediately. I would not fancy this job at all.
So readers of this note, and note well -- BE CAREFUL WHEN CHANGING BATTERIES! A second's thoughtlessness here will create hours of electrical misery. Always but always, PAUSE AND THINK around your battery.
Leedsman.

If the battery is connected backwards, you will have a dead short through the stator diodes in the alternator. Those diodes may be toast. You also may have burned open a wire connection at the battery, starter, or alternator. Many cars also have a "fusible link" built into the main power wiring. This is essentially a "main fuse" that is designed to burn open under events like reverse polarity.

The electronics may have survived this event. Electronic controllers are generally designed with reverse polarity protection circuitry, which amounts to a diode at the +12V input (cathode connected to the +12V input and anode connected to ground). Normally this diode does not conduct; however, if voltage of reverse polarity is applied, it conducts and effectively "looks" like a short circuit to the power system, thus blowing the fuse in that circuit.

If the new battery (properly connected) is not being discharged very quickly, then the diodes in the alternator may have survived OR the wires are burned open somewhere. Have your alternator tested. I believe places like Advance Auto will do this for free.

As others have said, your best best is to use a volt meter or a simple test light to determine if the connections are sound.

There is no fuseable link fitted to a 1993 Jaguar XJ6, at least not in my recollection. There will also have been no damage to the starter motor from the reverse polarity connection.

As for protection of electronic components in such events, I can only speak to its absence in the case of an X300 coolant heater pump. Reverse polarity was quite effective in letting the secret smoke escape from the unit.

Hi Jasont,

Hey, what was the final result on your reverse-polarity issue? I ask cuz I did the same thing while boosting at night. Next time, I will use a flashlight to see more clearly... ugh..

Martin

If your Jag's battery is dead , your hooking up should be like this

So, red means positive + and black is negative -
For negative connection you can use trunk hinge , do not hook it neg cable to the hood struts :icon_attention:

AHA, the Lucas closely guarded secret.

All Jag owners should know about this, it does make electrical issue sorting much clearer hahaha.


Attachment 18404

I cant say for Jaguar but newer Volvo's (98+) would usually be ok with the exception of the instrument cluster, they would usually get fried. Its very possible some expensive items were cooked.

If your VCM wont do a self test then you are going to have to just start from scratch and check all the fuses first and them start tracking down what doesn't work one thing at a time.

Toast ?
 

MarkC is right on the money in his reply. As a former Mercedes service mgr, and owner of several 560SEL's (ugly old brutes), and proud owner of a pristine '94 XJ40, I can tell you of my own event.

I was driving one of my 'brutes' thru Binghamton, NY, when I noticed that the charging voltage was sky-high. I knew that the alternator's regulator pack had shorted, and the alternator was dumping full voltage into the battery, which was steaming when pulled over and checked.

A visit to Binghampton's local Mercedes dealer (didn't know any good independents in that area) introduced me to a mechanic who decided to attempt jump-starting the car from a battery sitting on the floor. He reversed polarity, with the result that the car's ECU, ignition module, headlamp control, and many other items were instantly deep-fried. After much testing, and $3000 worth of parts (paid by the dealer after threat of litigation), the car was whole once again.

You will need someone with good electronic experience and patience to repair this; the ability to understand the car's electronic schematic diagrams is a must for proper, logical trouble-shooting.

Lastly, I wish you much luck, and offer a brief prayer that your XJ40 has better protection designed into it than did that blasted 560SEL!

Best -

Jeff

Thank you all for your helpful input. The detailed specifics are what is needed here and I appreciate your thought in providing them. I think I now have enough information (for various sources) that it is starting to repeat itself, which suggests to me that it is now time to move to the next step, which is getting to work. Specifically, I have started to troubleshoot -- pretty well along the lines described by jeffH. I have every expectation that this will be an ugly job but time is not a concern here. I've worked on cars for years and I expect the silver lining here will be that I will learn a lot ~ and that is always welcome. I already have the wiring diagram and a spreadsheet set up. I expect tomorrow will be Day 1 on this adventure in learning. Again, thanks sincerely to those who helped.....