Hi all I purchased my second Jaguar this one is a xjsc it a Jaguar Cabriolet it a project the 12v motor was bad so I transplanted a sbc 350 motor and trans and operation was a success my problem is I don't think the alternator is charging the battery I get 12v out of the alternator to the battery from the battery line going back to the battery but my gage just goes up a little just above the red line.. gas gage don't work either but that a story for another day so any help is welcome ..is there a site that I can go to for the electrical diagram for a 1987 Jaguar xjsc... Thanks for your time

 

Jaguar XJS' often had a problem with the engine ground. Try running a ground strap from the engine to the body/frame.

 

12volts from the Alt is not good it should be at least 13.8volts, I would say the alt has a failed rectifier diode.

 

Thanks..I'll check that..can you tell me the plugin on the on the 350 alternator ..where does that go or it doesn't matter.. thanks for your time

 

Thanks.. on the 350 the alternator has a plugin ..does that matter or where would it go..Thanks for your time

 

HI Warrjon,, a question, i just put a new alternator on V12 XJS,, seems to be charging at 14.3 volts measured at the alternator output terminal, but after a few seconds volt meter drops to 8 or 6 volts for about 1 second then back to 14.3 volts, like its cycling up and down!
any ideas that would help, battery measure engine off 12.5,, when running battery stays around 14.1/14.2 volts!

its a Mitsubishi alt ,but fitted OK, 3 wire internal regulater type.

ron

 

Alternators usually have 3 terminals as long as you have these connected you should be good. But I do not know what alt you have.

Ground
Battery connection
D+ for the warning light / gauge.

Newer alternators can have more terminals for pulse outputs and a lot of other things. These newer alternators will still work on older cars and the extra terminals not used.

 

Hi Ron,

6-8 volts seems unusual, it may be noise interfering with your meter. Check the voltage at the RH terminal post. The alt wiring goes to the starter motor then to the terminal post.

You say that at the battery the voltage is steady @ 14.1 which indicates the alt is charging and the battery is not fully charged.

I would not be too concerned unless the voltage at the battery dropped.