Help needed. just bought a 1995 XJ6 4.0l with an electrical fault. (price paid reflected this.
The seller had identified an ECU water issue as the footwell ECU had been removed and the connections were oxidised. I have cleaned these up and opened the ECU which appears sound inside.
The issue is that when I connect the battery (with or without the said ECU hooked up,and with or without ignion on) there's no power to anything, indeed the battery discharges immedietly, I have also tried a known good battery with the same result. Instant discharge although the readings recover upon disconection.
Any ideas?

 

Welcome to the forum MikeColl,

I've moved your question from General Tech Help to X300 forum. Members here with the same model will be able to help.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Cheers

 

Apparently you have a short to ground. I would start by disconnecting the power lead to the alternator.

 

Yes I agree with RJ.

And I would suggest that while investigating and checking that you use a multimeter to test for no continuity between + and - battery leads before reconnecting a battery.

 

After following the advice above, if you still have indication of a short in the power circuit, you can put a fairly high power lamp (like a headlamp) in series with the positive lead of the battery. That way, you can have current flow and not burn up anything including the battery. If a high load is there, the lamp will light. Disconnect fuses, relay, and wires until the lamp dims or goes out and you have found the offending circuit.

 

Hey sparkenzap that's a good new one for me. Thanks!

 

Many thanks.

 

Yes, thank you.

 

Yes, thanks.

 

Instant discharge? If your battery is any good an "instant discharge" is going to melt something, hopefully a fuse first! If no fuse failure I suggest the battery is dead, or, not "instant discharge". What do you measure which leads you to your observation of "instant discharge"? a voltmeter on the battery terminals?

 

Hi, this is what I use. it check condition at rest and under load My battery if fine disconnected but flattens the momenr I connect the car lead. Also me "booster pack" does the same.

 

That is probably a battery with a bad cell. A good battery can not possibly discharge to dead when connected without first melting the cables.

 

Hi Mike,

Welcome to the Jaguar Forums!

You've already received excellent advice from some of our experts. I would add that, if you don't already have it, you can download the 1995 XJ Electrical Guide here:

http://www.jagrepair.com/images/Auto.../jagxj1995.pdf

The guide contains all the wiring schematics, component location diagrams, etc., which should help narrow down areas where battery power shorts might occur.

Cheers,

Don

 

Thank you thats a big help, I'm used to the electrics on motercycles (have a couple) and some older cars (Land Rovers etc) but wow, these Jaguars take wiring to a new dimension. Will post pics today (of the car) in "introduce yourself).

Thanks all for your help. Still scrathing my beard. Still no power being fed to ant electrical curcuits on the vehicle. Suspect a main fuse so the wiring diagram will help a lot.

 

Correct