thanks.
i know i am in a rabbit warren and chasing my own tail here.
but i just want to try and check out every possibility and rule out everything before i get the alt rebuilt.

i currently have the battery on charge as it probably has not been 100% fully charged in a little while.

i did use the continuity test the check the diode only flows one way and that is correct.
(b+ to chassis) only one way got any reading.

when i have the car running tommorrow i will do an AC voltage test (b+ to chassis) and see if the is excess AC current.
i will also disconnect the noise suppressor when i get a chance and test if that makes a difference.

i will get under and try and find this centre bulkhead terminal as if there is a voltage loss it will be there (i suspect)
if i can i will get a long cable and run a temp test lead from alt b+ to battery and check if that makes any difference.

i did the AM radio test and there is no noise whatsoever.

it is all pointing toward bad voltage regulator.
but i don't wanna believe it.

 

Fortunately , the VR is 35 dollars US but work to get one removed and shipped timely in your area

The alternator test at the auto parts store should be free , even " on car " if it shows as a fault at that time , the alternator / VR inside will be warm for a valid test as well as you can know you have a high electrical load on it ( cabin blowers , headlights and such minus the stereo that you can bring on line as a variable )

My X300 was wrecked by the previous owner and the front right wheel quarter panel was replaced by him ( cabin to right wheel quarter panel starter / alternator battery cable pass through ) so that is my target on huge starter sag when I get " things " together

But the material in the people ( close location family ) I have to work with is " lacking " for a polite term , super lacking

It has an huge effect on my material but must persevere forward

 

The IN435 VRs that I sourced from E - bay vendors was a waste of time in sending me the wrong part # or the correct part# that performed worse that the original broke VR

Suggest get one from a brick and mortar business that has more skin the game than some kid in his mom's basement

The business is more invested in it's reputation so it has to put out a good product or they have more to lose than some kid that takes your money and says ..................next ...........move along

This was my source but then in the states :

Can't find the brick and mortar vendor ( maybe put out of bussiness by E - bay ) but here is one

Alternator Voltage Regulator and Brushes Kit for 1993-1997 XJ6 4.0L Vanden Plas - 13524RKa - Alternator Rebuild Kits

 

Can't find the vendor I used , and I most likely have the shipping receipt in the garage

 

not sure if auto parts stores here do those tests or not. i don't think so.

its a big shame when we can't rely on those around us to help.
I really hope you can eventually get your issues sorted on your CAT.
atleast mine is driving well and i am slowly fixing the issues.
she is running A LOT nicer now.
fuel economy has dropped right down and I have had no issues with her running lately.

 

will def keep that it mind....
might be worth buying the VR, the bearing and the rectifier.
obviously hoping not to buy anything. but looks unlikely.

 

It did but I have a battery cut off switch I use because this car is not a daily driver it took the help of Parker 7 to locate the problem. The amp meter was also showing discharge and like a fool I replaced the alternator thiking that was the problem

 

When if fried my alternator by placing the main battery in backwards ( mad at family at both times I did this ) it fused one of the VR electrical tabs that ties into the brush tab so had to replace brush ( cheap )




You didn't do this but as a heads up in ordering parts

In Sydney there should be an alternator rebuild shop that can source the parts for you ( maybe be on hand also ) so you can rebuild yourself . You can build a relationship with them and they can also give some technical advise that an auto parts store can't

My alternator was at 110, 000 miles and the brushes were at 1/2 wear

I did have these same folks at a later date replace just the main front bearing as it went out ( 28 ish years old or loaded up belt too tight )

If you want to clean up the power that goes to the VR to make power..............

Comes from fuse # 10 in the right engine bay fuse box ( " counterfeit " fuses made of wrong metal can limit current to the VR without blowing ) something from somebody else way back

This same fuse # 10 is unfortunately shared by other items unfortunately ( bonehead engineering )

There is a ribbon connector attached to the underside of the fuse box , you have to flip the fuse box

If I recall the wire passes through the Papa Indy 61 connector pin 2 subject to a TSB ( for the whole connector ) for corrosion

See the splice that can limit the current without blowing the fuse

If those other items are shorting out it would eventually blow the fuse and then no alternator generation / 0 ( this has happed to others and missed fuse )

The question becomes what if the draw from the other items is up to the point of just before the fuse blow , does this have an effect on the available current / voltage to feed the VR

We'll get your electrical generation game tight

 

When I attempted to split the alternator casting halves I cracked the casting doing it without heat to expand the mating halves seam

But here is an overhaul kit with bearings

Alternator Rebuild Kit for 1993-1997 Jaguar XJ6 4.0L, Vanden Plas - 13524RK - Alternator Voltage Regulator and Brushes Kit for 1993-1997 XJ6 4.0L Vanden Plas - 13524RKa

and

Innovating Bearing Manufacturing | WD Bearings Group

 

There is the history on the alarm sounder ( 3rd back up alarm horn incase main car battery disconnected / Fort Knox system ) in front of the window washer fluid fill cap shorting out

This is a rechargeable battery , it's battery charger and horn inside that gets moisture inside ( sealant / potting age ) from the gaps letting rain in the headlights trim

This will start corrosion inside

First try is to just unplug it

And then you can pull the 3 relays

And last the windshield washer jet nozzles heaters which was the case with CDMAs alternator issue ( blowing fuse # 10 )

 

The source link I gave before is the same company in Dallas , Texas that just changed their name

But the IN435 number has been replaced , this should be the same VR in the overhaul kit with brushes and bearings

Regulator Replaces Denso 126000-1200

Product Description

Voltage Regulator Specs

Premium Aftermarket Transpo or Regitar Regulator, 63.5mm Mtg. Length, Active lamp function - with output., For Denso IR/IF Alternators, 12 Volt, A-Circuit, D-IG-L Terminals, 14.5 Voltage Set Point, w/ LRC

Replaces

Denso 126000-1200, Isuzu 8970320910, Jaguar JLM-11144, Other: 230-52072, VRH2005-16A, and ................................IN435

Jaguar part # SPD5067 which crosses over to Jaguar JLM-11144 on the Classic Jaguar Parts website

There is a IN435 stamp on the back on the original part and back then I did receive a IN435 stamped part


JLM11144 - Jaguar Regulator | Jaguar Land Rover Classic Parts see technical drawing on the websites 2nd drawing

They didn't make it easy

 

Thanks for all the help so far.
the biggest thing that confuses me is why the alt generates full power after a cold start.
then lowers once warm.

makes me think that it is not something like the brushes.
and more something like the diodes.
Generating too much ac current or something along those lines.

So yeah checking the voltage this morning when car first started altenator was 14.5
then a/c turned on and it dropped to around 14.
then when car is warmed with ac off it went to 14 also.

so the alt “can” reach full power.
lots of fluctuations whilst driving.
in d v in park.
moving v stopped.
ac on v off.
practically everything.
so i am seeing it as literally only one of 3 things.

diodes causing too much ac current.
vr slow/unable to compensate for loads.
bad wiring between alt and battery. (Which will be a hell of a pain to fix)


one of the most annoying thing tho is my dash cluster reads a little lower that accurate.
it will appear to be at about 13 when batter voltage is actually at 13.5

 

The VR IN225 is the brother to IN435 as IN435 is a faster response time to stay voltage stable on the low bass notes that take a lot of current so battery draw

The diode package can be tested " on car " at the auto parts store with their mini hand held meter but you did a AM radio test

The noise suppressor removes more AC ripple that is left over from the not perfect by design and physics limitations diode package but then you did the AM stereo test

The alternator windings produce 100 % AC to start with before the diode package converts the AC alternating sine waves

Voltage is a force or like water pressure , and power is .......................voltage times current ( or the amount in a water bucket in comparison )

The terms are easily mixed around in conversations

I was accused by a professor in " true " engineering collage of cheating on my 2nd semester physics on my final examination and denied my score , so I did get the fundamentals of what was taught as I " put in my work / study time / brain ability " as I told him , My engineering collage required a lot of work for everybody and high drop out rate

In England and other countries , a licensed aircraft mechanic is referred to as an engineer but not fully true , not even close in depth of studies or task of design

" one of the most annoying thing tho is my dash cluster reads a little lower that accurate.
it will appear to be at about 13 when batter voltage is actually at 13.5 "

This has to do with where the gauge reads as a test point along the way , at rest ( no engine running or device like headlight drawing current ) there is no Voltage / current effect and the battery cable voltage readings will be the same as the battery terminal ( no alternator turning ) or the higher alternator ( if turning ) so this throws people off in confidence right at the beginning of troubleshooting

There is also the accuracy of your testing devices as even my meters where required to be sent away and calibrated yearly and always a calibration sticker per regulation in aviation , there is always your testing devices connections to your subject item as well

 

Multiple testing devices giving the same readings.

 

so. i may have located a point of voltage drop.
so ALT B+ --> STARTER ---> RH Firewall stud.
now when i probe alt b+ i get true alt voltage. ~14v (14.4 at time of testing)
when i probe RH firewall i get lower voltage. (13.8v at time of testing)
when i probe connection at starter i was reading 14.15v

so it looks to me like starter motor connection is a point of resistance causing voltage drop.
not the problem comes how the f*** to actually undo and clean this connection without removing the intake manifold.
not much room to work there.

yep definitely a voltage drop at that connection.
i just put my multimeter to prob the voltage drop between starter and firewall and was only reading a .05v drop. which does not add up to the .5v difference when probing each connection individually.
but then i realized. my multimeter probe at the starter was sitting between the cable from the alt and the cable to the firewall and my system voltage was going up from 13.5v to 14.2v.
so just the small extra contact from the multimeter probe was creating a better connection without the same level of resistance.

 

The starter tie point is from underneath with a 13 MM socket on a 3 inch extention

Your fingers will be your eyes

Remove battery positive post first as hot

Pic in above post # 5 and below

Bed time in the states

 

ok. so update.
finally got a chance to get uner the car and have a look.
undid the connection at the starter.
cleaned the connections with CLR and a wire brush.
did it back up.

started the car.
Alternator read 14.5v
Battery also read 14.5v

now to keep an eye on it as i drive around but looks good.
even if there is another issue this was certainly the issue causing the voltage drop between battery and alt.

 

Someone got that pic easily seen from above as a check on the starter solenoid tie point that is worth a 1000 words