I am swapping alternators between my '86 and '85 XJSs. (The one in '85 is not charging, so my plan is to put in the alternator from '86 which was working before the car was parked for good.)

I read the repair manual and other available references.

First step was to remove the air pump (because it is in the way.) This step was fairly painless (by Jaguar repair standards.)
- Removed 3 bolts from the front of the pulley, then removed the pulley
- Slackened the adjuster bolt
- Moved (pivoted) the air pump away from the engine as far as possible
- At this point the metal bracket to which the air pump is attached became visible.
- Slackened and then removed the pivot bolt and removed the air pump.
- Last step was to remove the metal bracket (because it is in the way) by removing the four bolts

Here is the air pump and the bracket taken off the engine:



Now I can clearly see the alternator:



As it was getting late, at this point I decided to stop for the day. Didn't want to rush things (because mistakes are made often when rushing.)

The next step, according to repair manual, is to slacken the nut securing alternator mounting bolt. Is this the nut the arrow is pointing to in the picture? It seems access to this nut will be challenging. How can I get access to this nut? Any tips?

Assuming I can somehow get to this mounting bolt, the remaining steps (adjuster link and trunnion block) are done by accessing from under the car, right?

 

When I did the myriad of alternators, before the Bosch upgrade, and the fact I have an idler, not that pump, I did it all from the top.

The bracket still needed to come off.
The RH radiator hose came off.
Then by reaching down, basically laying my belly (smaller then than now) across the guard, all the nuts, bolts are accessable as best Jag intended them to be.
I did wash the front section down prior to beginning that task, and then I CLEANED everything 100% prior to reassembly.

It is not easy, and taht is fact. The first one took me all day, but then I had them out and in withing 2 hours.

The mechanical fan is a mongrel for access, and that will test your patience. I went Efans after the first one, and that opens up so much room, a party could be held in there.

The alternator adjusting etc from under the car may be accessable, but I found by using the "feel" method from above just as easy.

 

FWIW, I have just changed one, thus the pain is fresh in my mind. The long bolt your arrow shows has to be loosened using a spanner at each end. Also the small bolt that the adjuster rod fixes to on the bottom front of the alternator. From under the car (I found that much easier) the adjuster has to be loosened and also the fitting piece bolted to the engine that the adjuster pushes against. The alternator then must come out from the top. the spanner sizes involved are 1/2 A/F and 9/16th A/F, use the ring spanner end of the spanner wherever possible.
It is well worth installing an extra earth wire from the fixing bracket to the lower chassis rail too. But the real fix is a 115 amp alternator!
Greg

 

thanks all. I finished the job today. Took the alternator from my '86, then took everything out from '85, and then finally put the working alternator '85. Just like you all said, it is doable, but sometimes you have to go by feel. Also, it is helpful to have a bunch of different 1/2 and 9/16 wrenches available: different lengths and shapes. Those will make the job easier.

Here are the alternators on the bench (the working one, from '86, is on the left):



Yeah, I think it would be doable in 2 hours (after the first try). I would have finished in 5 hours, but then when I was reinstalling the alternator, one of the alternator wire connectors broke. I cleaned up and shorten the wire, but when I put the alternator back in again, the connector broke again. At that point I had to improvise and created a "makeshift" connector because I was determined to finish the job today. It finally worked on the third try. Phew... But I spent about an hour and a half dealing with this damn piece of wire...

In the end, it all worked out. Started the car -- no more Lightning Bolt warning light on the dashboard!

After that I took my kitty for a drink:

 

Well done.

Crispy wiring, FIX IT PROPERLY, or that "new" alternator will follow the other one very soon.

Its a V12 thing, and crispy wires are the test of your LUV for the car.

What was your rewarding drink?????, MMMMM.

 

Nice!!

 

The wire that broke (twice!) was the ground wire. Interestingly, the design in my '85 was slightly different from '86. In '86, the ground wire was a thick black one, culminating in a very solid/massive metal connector. It looked and felt more solid.

In '85 there were two brown/orange-ish wires coming from somewhere. They were thinner. And crispy, as Grant put it. (Crispy is a good way to describe these wires.)

Since these appear to be just ground wires, can I just run another (new one) from an alternator to a nearest ground point nearby? Wouldn't hurt, right?

 

For the purposes of this conversation it's safe to say that 'ground is ground' and there's no problem with bypassing/abandoning poor existing ground circuits and replacing them new, good ground circuits. And adding redundant grounds while you're at it is never a bad idea on these cars, by the way.

However.....

"Since these appear to be just ground wires" is not very reassuring. Better find out what they are, definitively.

Cheers
DD

 

I learned long ago that a good assortment of terminals, a soldering gun, shrink tubing, and a variety of spare wiring is essential when working on old cars....and triple-essential on old Jags. I go into any task with the assumption that I'll have to repair or replace some faulty connectors or bits of wiring.

My assumption is almost always proven correct


Cheers
DD

 

BE CAREFUL. On my car and most HE pre facelift OEM V12 setups, these two wire are the ones that connect the alternator via the starter to the battery positive. That is, they are the main charging wires. For some reason Jaguar fitted a dual wire setup in place of one large cable. They go through a protective tube to the starter positive terminal. If they are coked, replace them with a larger diameter cable.
Greg

 

10 mins is all I needed to install mine...

 

I had my doubts about the orange wire being a ground. Orange is not a typical color one would use for a ground wire. But there were only two wires coming to the back of the alternator: this orange "double" and the other one, which is black. (I wish I took more pictures.)

I could not trace the orange pair very far as it "disappeared" along the block. The black one I was able to trace to a panel box attached to a fender, near the firewall. I saw bunch of relays inside that panel box. So, I assumed that the black one was hot wire. Applying principle of elimination, I figured, the orange pair should be the ground.

I guess I was wrong. Thanks for correcting me.

 

Gregs warning is REAL.

Those paired wires are battery HOT as long as the battery is connected. They travel via a steel tube, under the RH exhaust manifold, to the battery connection of the starter solenoid, and the heat in that steel tube will degrade those wires after 30 years. NEW wires here is very smart.

The smaller wire you have is commonly known as the "excitor wire" and is 12v live when the Ign is ON, engine OFF.

Since the recipient is a 1986 car I would suggest it may be the start of the installation of a load dump module, some markets got them in late '86, we saw them in late '88. Many, many write ups about that fiasco in here, and the subsequent removal of that thing to stop silly lights flashing on the dash cluster.

There are NO factory earth wires on the alternator, it earths via the casing and the engine, then the 2 earth straps around the LH engine mount.

ALL my Jag have EXTRA earth wires all over the place, and that sorted the Aliens to the point they departed. Even my 2 S Types have extra earth wires.

 

Got it! This makes sense! Why don't repair manual explain this clearly???

I thought that out of two wires, one must be ground wire. Especially for such an important piece as the alternator. It did not come to me grounding can achieved through the casing of the alternator! Hmmm... theoretically it should be possible. It just didn't occur to me. Live and learn.

 

Electrical assumptions are as bad worse than any other kind. A... u me !!!


Black is almost always ground. Multi colored wires denote a load of some type.


Unless a PO or other has "monkeyed" with the circuit. Then Jokers are wild.


When I "converted" my car, I chose to buy a custom new harness. Not cheap. But, driven a lot by the poor condition of the original Jaguar wires in the engine bay.


Errors, misleading labels, poor documentation caused me a lot of pain. One was two wires with ringed ends, black!! Gotta be ground. No power in he system... TC with maker. No, those are power and have fusible links!!! "Sorry, I should have put colored tape on them!!!




Yes, I've been hooking up wires for decades. Gotten much better at it as time has past. From the days of twisted splices, sans solder, covered in cloth electrical tape!!!


Shrink tubing was a great find for me.


I've a couple of tool boxes among others, electrics related. One marked "SOLDER TOOLS, the other "ELECTRIC TOOLS".


And, many spools of wires in various colors and gauges.


Carl

 

UPDATE: Driven the car locally a few times after installing the alternator from '86. Lightning bolt warning light has not come back. Guess it is a good sign.

When I measured voltage with DVM at the battery with engine idling, I got 12.7V to 13.0V (occasionally), but mostly slightly below 13V. I thought it was a bit low, no? (When engine is not running, I am getting 11.7V - 11.8V from the battery alone -- guess the battery seen better days.)

But still, should I be getting 14V or so at the battery when alternator is charging? What others get at the battery on their XJSs? Just curious

 

That sounds dead right. It will go to 14 or so once the revs rise. I have one of these stuck into the cigar socket, well worth having so you can see what is happening while you drive.



Greg

 

I thought Black was ALWAYS ground.... cars, stereos, computers...
then I bought a HOUSE...
opps... BLACK is SUPPLY hot and white is return and green is ground... and green yellow