Greeting!
My first post -- thanks for your help!
Had my 87 XJ6 4.2-6 sedan for a few months. Has a few problems and this is the more pressing. Voltmeter on dash wanders up and down. Mostly off-scale low then now and then up to almost 13V. Encouraging urgency, yesterday I drove the car and after driving 30 minutes and stopping the car for 15 minutes it would barely turn over and did start (phew!). Also, when I was driving once a month ago at night it seemed that the headlights were very dim and at that time the voltmeter was pegged low. Battery is a couple years old.
I have experienced the benefit of cleaning and retightening contacts and connectors in the electrical system with other old (English) cars and some pointers on where I could look and what to look for would be helpful. Is there a diagram or legend of where electrical components are located somewhere? That would help me greatly! I have a Haynes book and a tech pub Series III Service Manual and don't see the information there.
Your help is very much appreciated

 

What you need is the S57 wiring guide. When Jose sees this he'll give you the link to a download. Or let me have your email address via private message and I will send it to you.

In this case I'd check the connections at the alternator itself and at the two "+" voltage junction posts on the firewall. Also check the main ground strap under he car, RH side, right about where the engine and transmission join together.

There have been some cases of the main alternator output wire....the one that goes to the LH junction post.....developing excessive resistance due to internal corrosion.

Is the alternator belt tight?

Cheers
DD

 

I bought one of these voltmeters because I liked a digital reading and it's instant response. Works great!

 

I thought I was smart and made something like that. A patch cord for my VOM. Connected at the cigar outlet. volts in real time and under various loads and RPM's.

Plus an added ground. From thje battery - at the right wing wall to the engine. in my car at the alternator.

Aye on the S57. learned so much and got a lot of aid there.

Put the Haynes in retirement I was thrilled early on, then disappointed and confused.

 

Thank you Doug!

I will look at all of these items. Say, I attempted to download S57 from the page download post on this page and the link may be broken. As you suggest, I will PM you and greatly appreciate your personal attention!

 

Hi Doug, Seems I don't have the ability to pm you -- I am still researching.

 

Thanks Doug.

download free Factory Service Manual and S57 Wiring Guide here:

https://jagupgrades.webstarts.com

 

I would have the Alternator tested, it sounds like a bad voltage regulator.

 

Hi Jose -- Many and many more thanks!!!

What a wealth of information you are sharing to me. I appreciate it!

 

Thanks. I just got very busy in other directions and fortunately the jag is my toy for free time. Anyway, I plan to try the in car tests first. Off the top of your head do you know if the diode pack is replaceable?

Many thanks!!

 

Phil, you are very welcome.

Doug knows more about the Diode Pack. I believe it is.

 

I'm sure the diode pack in the alternator is replaceable. It's probably called a rectifier.

We don't typically see the usual vendors selling repair parts of the Lucas alternators but am I sure the parts are out there somewhere. After all, the alternator repairs hops have to buy the parts from....somewhere. Might take a little digging


Cheers
DD

 

Thanks! I'll buy one.

 

Say -- I think that I need to go on a connector and ground point clean and tightening mission. Pending your recommendations, my plan would be to be methodical using the S57 diagram with a bias towards accessibility and problem areas. What cleaner is available now and do you recommend wire brushing or some type of emery cloth?

Many thanks!!

 

For earths (grounds) I recommend cleaning the body and connector to bright metal, with a file or a metal toothbrush or emery paper, then clean with contact cleaner, then attach the earth and then cover with white grease from a spray can or special contact grease if you have that.
For connectors the same except for the grease.

 

Faulty rectifier will allow battery to discharge over time. Both rectifier & regulator are easily replaced. Use long nose pliers to act as thermal shunt on rectifier diodes when re-soldering. Take photo of old regulator wiring before removing, some manuals not really that clear.

Try these people for parts: https://www.ebay.com.au/itm/NOS-LUCA...4AAOSwW55bY2Su

Cheers @ beers!

Peter.

 

Thanks for your helpful comments!! Here is my update.

I found that the battery was very dead. Removed, recharged and tested at AutoZone satisfactorily. I don't know the age of the battery but it is a newer style AGM battery. I have visually and electrically verified some of the terminal locations and all seem fine. With the battery installed and an ammeter from the battery negative to car earth I get about 0.12 A for about 10 seconds and then it drops to 0.0 A. Started car and at idle battery voltage increased to almost 14V on dash meter. I have determined that my old Volt/Ohm Ammeter or its leads are not reliable and I'll get a new meter over the next couple of days. I am a little skeptical of operating the car and pulling the positive battery lead to verify adequacy of the alternator output (??).

It looks like a challenge to remove the air pump and A/C compressor to get access to the alternator. Is there an easier way?

Many thanks to all!!!

 

best to remove alternator from below which will.also be a pain.

Raise front of car and place jacks under front suspension. Use hydraulic jack on one side jacking point and tire jack on the other for double safety.

 

From the bottom, as Jose mentioned. But, still. it's no pleasure cruise

It's been a few years since I last removed one but I remember a few tidbits:

Disconnect the anti-roll bar end links and LH side -u-bracket. This allow the bar to swing out of the way.
Disconnect the alternator main output wire at the "+" post on the firewall and remove the small clamps holding the wire to the body. This allows slack in the wire which makes it easier to disconnect it from the alternator.
The oil cooler hose might interfere with dripping the alternator out. If so, remove the clip that hold the hose to the subframe so that the cooler hose can be repositioned slightly
Using a 1/4" drive docket set allows easier access to the alternator bolts

Cheers
DD

 

it is general knowledge that when the alternator goes bad, it kills the battery, and when the battery goes bad, it might kill the alternator.

your symptoms are typical of a bad alternator killing the battery.

replace both. Yes it is expensive. But do you prefer to go through r & r the alternator and keep a possibly deffective battery ? You might end up doing the job twice.

Start fresh with a good alternator and battery.

after you raise the front of the car, remove the Splash Guard, then you can see what a beautiful mess you have to deal with.
I did it once, it is doable. I spent more time cleaning and detailing the Splash Guard than replacing the alternator. Use a head-strapped flashlight too.