Hi everyone. I'm new to owning a jaguar. Never worked in one till I had to do an engine swap on this one (2002 x type 3.0 manul). I have been searching your forums for a?while to get answers I need. (Been my biggest help!) My current issue is I just installed a new alternator let it run in the drive way for about an hour while fixing other small issues. I drove it about a block and the light popped in. After checking fuse 82 and finding it was popped I tried to replace it with the key on and it would immediately. I took my multimeter and checked both leads to the fuse and It showed a voltage So I new there was a short. So I unplugged the alternator (brand new) and replaced the fuse (this was a few day later got busy) and the fuse didn't blow. Is it safe to assume the new alternator is faulty or did I miss something?

 

Blindman, first off, if you measured the field with a normal multimeter, it will read a very low resistance. So, that is actually fairly normal. As for why the fuse blew when you put in the new fuse is that you had the ECU trying to raise the voltage and it had the field voltage at maximum. With the extremely low field resistance and the "high" voltage coming from the ECU, that would generate enough current to cause the fuse to fail. Where the problem comes is when the field winding is spinning, it is also acting like an alternator and it is putting some resistance into the wire, therefore reducing the current that can flow. Hence why all is good now. I don't want to get into much more detail than this as you start getting into electrical theory and it can make your brain hurt if you are not familiar with things.

 

That I understand and I know it should read somethimg. But with the key on (engine not Running) should it really blow a 20 amp fuse? And make the wire start to smoke with a 25amp.

 

Blindman, if the motor was not running, then I would not expect it to blow the fuse since the ECU should shut down any voltage going to the alternator. So, I would suspect that you either had an issue with the field wiring (ie, wiring issue in the plug on the alternator) or there was an internal issue with the alternator (ie, wire inside is touching the case of the alternator).

Please keep in mind that Fuse 82 is only a 10 amp fuse and by stepping up the fuse rating, you risked a fire in your car (as you saw from smoke coming off of the wiring). With modern day cars, they are using the smallest gauge wire that they can and in a lot of cases, the wiring is undersized for the fuse, so, it will run warm. You put in a bigger fuse and you can easily turn the wiring into a heating element.

 

Thanks thermos. I'll have to take the alternator back out and check the wiring to the plug. I'll have to buy more fuses (blew the last of them trying to get it home) will have to wait till tomorrow. Or the weekend. I will keep you guys up to date

 

I got the alternator out and it passed the test at autozone. Any ideas where to check for a short?

 

Blindman, unfortunately, this is where you get into the dirty work and you need to start hand over handing the wiring to see if you can spot where there might be some damage. I would also start with the plug to see if the pins are still silver in color (not a brown/rust color).

 

Did it work for awhile after the motor swap, or this is an initial issue at start up?

There is a jag publication, name escapes me, but it has a very thorough procedure for checking for the issue, just alot of unplug this, read meter, swap leads, is volts this, is ohms this, if not fix it and continue.

 

Well ladies and gentle. I have found the problem. The wire harness for the steering servo had broken free and landed on the exhaust and burning completely threw. I have fixed the wires wrapped in in fiberglass matting and electrical tape and zip ties the crap out of it. Figured since I was this far in to it I. Would replace the intake and valve cover gaskets put new violent temp sensor in clean the **** out of. The intake rewrap the entire harness and flush the coolant system, and give it an oil change. Hopefully I won't have any issues this winter.

I appreciate all the help and look forward to reading more post and trying to help when possible

 

Dandy!!