So i am looking to try and make sure my electrical system is in top shape as i have had some voltage issues and current draws (hopefully all in the past)
i just swapped my alternator with the one that was in my parts car.
now when it was in my parts car the guage was showing close to 15v,
now it is in my car it is 13.5 to 13.9v
so not bad, but definately lower than it was in the other car.

so i am looking at 2 things.

firstly swapping the alternator noise suppressor.
where exactly is this located?

and secondly looking at the big 3 wiring upgrade.

now number 1 is easy upgrade. extra short wire in the boot.

number 2. where is the engine ground strap located?
is there even one? or is the engine grounded via the the engine mounts?
also when swapping the alternator it does not seem that there is a ground wire that matches that of the big b+ cable.
no big ground cable i assume it is grounded by the alternator housing and the mounting bracket.


number 3. PITA to try and run an extra cable the entire way.....

 

The noise suppressor is under the car to the outside car direction from the alternator , it's a tall round cylinder , not all X300s have this from reading others

It is the small wires you attached to the alternator and there is a proper place to put them on your alternator shell , I ask a professional alternator rebuild shop and would have the refresh my memory

Someone in England had a great pic as installed from above with no engine or alternator

" 13.5 to 13.9v " is on the low end of good so will have to think about it , round 2 wire connector as you placed it on alternator cleaned and maybe with abrasive action ?

The engine ground strap goes from the starter lower mount bolt to the car frame rail

B1MCP has a good pic of it , 13 mm shallow socket on a 3 inch extension and 10 mm socket on the car frame before you dive under there . you may have to pluck the oil dip stick tube out of the way and of course something is attached to the tube , ensure you have dip stick tube properly reinstalled as can error getting into seal

 

wonder if it is possible to unplug and clean connector without again removing alternator....
not sure if there is enough room and my hands an make it happen.
its definitely something on the car side of things that is giving the lower voltage as i know the alt was higher in the other car.
was thinking there could be dirt and oil build up around ground connections.
i do my best to keep my engine bay clean but cleaning may have pushed dirt somewhere it doesn't belong. esp when i previously had lots of oil build up around when i got the car.

the wires on the alternator i put back exactly where they belon. one branches off and goes to the main b+
and the other goes onto the small 8mm nut below.
that wire is way too small to be ground tho.
it does not even come close to matching the b+.
the alternator must ground to the engine via its mount..... else it would have a ground so small it would cause shorts.

interesting you say near the starter. it seemed the wiring book shows it closer to the front.

will check both cars for the noise suppressors.

so many things to do atm i want time off work to do it. atm only having sundays is not enough time to get much done.
looking to clean the injectors and put them in on sunday aslong as my supplies come.

 

The small hole wire ( Black ) eventually as it comes from the suppressor goes to car frame ground per the wiring guide ( not always represented correctly ) , either by the shell ( A ) of the alternator ( as the mount bolts are grounds ) or an exposed isolated small post ( B ) as it emerges from the alternator core ? as that was a question to ask a professional in the area

The B + post is defiantly electrically isolated from ground and the ground path small wire from the suppressor at the alternator has the same representation as isolated but then a small dot below as a representation of case electrical tie as in wires commonly used ( over thinking )

[x300] ...suppression module? Eh? - X300 - Jag-lovers Forums

Inside is a giant light blue 44,000 pfd ( units correct ? ) capacitor with ornaments , it's a beautiful thing for an electrical guy as we used to blow them up in collage plugging into wall socket

But I was not an Electrical Engineer in collage

Additional thinking : note you do have the diodes ( bridge rectifier ) inside the alternator to convert AC alternator winding output to mostly DC but not perfect as some AC gets through ( ripple term ? )





Does the ornaments atop the capacitor inside the black plastic shell act as a rectifier of the unwanted AC current ( pure DC wanted as it is also in the wire ( Brown color ) at the same time but the wire acts as an AC bleed off to the capacitor in the noise suppressor to ground as an extra measure to remove AC " pollution " )

otherwise , you would hear it in your car stereo on an AM station , final good noise suppressor as itself test

You can do this AM radio test before doing anything with your current suppressor , now what this tells you of your low alternator voltage reading ?




AC Voltage Capacitor - Capacitive Reactance, Capacitor Working, Derivation and FAQs (byjus.com)

" its definitely something on the car side of things that is giving the lower voltage as i know the alt was higher in the other car. "

Was the running car reading good voltage ( 13.5 to 14.5 ) before it failed if you can recall ?

I do have a removed alternator rear cover and disassembled core of the alternator to track ground path I can take a pic of

Notice the small post almost touching under the large B + post and the 2 post bridge on B as the post hole contacts the rear cover

 

So much nerd talk above.
love the engineering stuff.

I can’t recall exact voltage in car before i began to notice the fluctuations.
Can’t recall if gauge was reading just above 14v or just below 14v

what i do know for sure is that i am sometimes getting the 14.2v reading from my alt.

my suppressor is connected to the post you have circled as A. Which is where it was connected to in both cars.
not sure if there is a difference between a and b.

I am not sure if the suppressor can have an effect on the voltage or not.
i am leaning toward ground wire atm.

when i get a chance i will def upgrade that cable.

From factory there is a large ground cable from back of head unit to car chassis.
that large ground wire is no longer connected as after market unit had nowhere to connect it.
i assume all that does tho is help ensure the stereo gets good ground to reduce radio interference.

 

So the current alternator on the running car after swap sometimes reaches 14.2 volts ?

Not sure about B circle as don't recall short bridge piece , will have to look at my spare as I took the alternator apart

A short way from the suppressor there is an the 2 suppressor wires connector you can unplug and see how the alternator performs before removing suppressor ( you may see the effect on a AM radio station on throttle up )

connector is still under car but may not have to jack it

 

Yep. On startup this morning it was at 14.2 initially.
then after a little dropped down to 13.9.
then was fluctuating from 13.8 to 14.1 depending on engine revs.
once or twice dropped to 13.6 when stopped at traffic lights. I could try and record the volt meter whilst driving but that is going to be a long video.

 

As i have noticed my cluster reads slightly different to my volt gauges i have installed and my obd reader i am also going to swap my cluster to see if the gauges are off.
the rpm and speed both read slightly different to the obd readout also.
rpm and speed read slightly higher, and volt reads slightly lower. Not sure if just general inaccuracy of the analog gauges or not

 

The OBD reader is probably reading voltage as the power pin in the OBD 2 port

The RPM and speed are extracted as a digital address ( section ) from whole digital string the ECU serial data bus is as it runs through the OBD port ( data link connector ) as a dedicated pin so the accuracy error may be in the ECU which you changed

The lower volts may be the terminal connections on the way to the OBD 2 port like a battery cable terminal connection ( not on the battery or " first " mega fuse terminal post right at the battery as the alternator is higher volts powering things)

See page 183 as the Orange and other wire Pink color , Orange pin Papa Indy 105 -10 at the ECU

jagxj1995.pdf (jagrepair.com)


You can calibrate the speed against a HI way kilometer marker and a watch ( second hand ) , factory tire size and correct inflation ?

 

I have a gps heads up display and i know that shows a speed slighlty lower than my cluster. Matches more with what the obd reads. Cluster reads slightly higher. Only by like 3-4km
voltage maybe out by .5v and rpm out by maybe 50rpm

the slight inaccuracy does not bother me as it is small and of no consequence.
but if it can be remedied easy then great.


and yep the obd def is reading from the voltage pin. It is the voltage being supplied to the reader

 

ok. i think jags just love doing our heads in.

firtsly i noted just now my speedo matches gps speed and it appears the OBD is incorrectly 5km/h lower
secondly i noted that the voltage actually was matching the gauge and the OBD
so that leads me to think the OBD may be showing the incorrect rpm and the gauge maybe is correct.
obd 580 gauge ~620 at idle.

either way does not matter.

also when starting my drive today voltage was 14.1.
then most of the drive was around 13.8-13.9.
toward the end of the drive it was about 13.6.

will report back on that after i get a chance to check the ground cable and the suppressor.

 

Just noticed my voltage even dropping as low as 12.5v while driving toady.

so i checked something i forgot about checkin previously.
firewall connections.
one positive looks ok, but the main positive on the drivers side is all rusty.
could be a potential cause.

 

cleaned em up with some clr, replaced the nuts..... lets see. i think there will be do no difference but heres hoping.

 

The 2 smaller ground studs one on each side on the rear firewall as an ECU and sensor ground point ( s ) are probably in the same shape , this is more important the then larger power studs

On the larger power studs remove the battery cable and wiggle the post , this lets you know if the battery connection on the cabin side is loose , found before

That one centered in your pic looks like the combination single cable starter cable / alternator cable from alternator back to the battery , located on your right wheel well

 

yes that is correct.
and yes it does wiggle a bit.
i tried to tighten the nut on the post from under bonnet
but i could not. It just kept turning. Its not very lose but there is some wiggle on the stud.

need to find the other side of it in the cabin

the smaller ground studs look ok.
gotta get under the car on the weekend and check the wiring from alt to starter, starter to ground, starter to firewall.
if all that checks out and i still have issue. Fire wall to battery is going to be a pain to check.

 

" and yes it does wiggle a bit "

Skip the cabin side as it is way way up there from the cabin

The cabin side is protected from the elements so should be in good shape minus arcing on loose connection

Remove a nut from one of the other studs good position , back the to work position spin nut out toward the end of the stud , place the extra nut on the end and tighten against each other the original being worked stud nut , so you will now have 3 nuts on stud , clamp the 2 furthest nuts to each other and clamp the nut pair and tighten the nut closest to the firewall / wheel well sheet metal , this will tighten the connection behind the sheet metal

Both the firewall and 3rd right wheel well terminal post / stud have been found to come loose and the 3rd wheel well terminal post is more prone to the elements and the outer stud / terminal post insulators have been found to be compromised

This short to car frame ground effecting alternator reading and battery charging and the rest of the car voltage , it would drain battery as directly connected through to positive battery post

 

ok...
so going to keep an eye on this now once i start driving around.
so i upgraded the ground cables.
I added an extra 4ga ground strap from battery to body, and from engine to body.

The bolt on the starter that the ground strap attaches to was badly rusted. all up the thread. was an absolute ******* to get out.
so i cleaned it up.
could not really clean out the thread too much in the starter/trans.
but i sprayed some wd40 in there and then screws and unscrewed the bot a few times so hopefully that all helps.

but in short both ground straps are now upgraded.
I check the voltage on the back of the alternator B+ and was getting a beautiful 14.54v at idle. so the alternator itself is working perfectly.
when i check the voltage across the batter i am getting a reading of 13.9-14.1 some small fluctuations.
so a voltage drop of about .5v from alt to battery.

not sure what the actual normal expected voltage drop is on these given the length of run.
but if she is staying at 14v then atleast all is good and there will be no issues

 

Funny thing i've noticed that my car yesterday dropped the voltage to 13V. Found the firewall ground stud loose. No rust on it so just tightened it up and protected with dielectric grease and it's back to 14.3.

PS Day ended with an unusual failure. A/C was weak since i've got the car month ago so went to my friend for recharge and we've got only 0.9 lbs out so refilled the system with 2.42 lbs per manual and on my way home the trinary switch has opened from its back spraying the agent all over the underhood. Couldn't find a better reason to wash the engine bay and it is still glowing green under the blacklight :-) Ordered two switches (used oem next week and some new they said 10 days to process after the payment received)

 

" PS Day ended with an unusual failure. A/C was weak since i've got the car month ago so went to my friend for recharge and we've got only 0.9 lbs out so refilled the system with 2.42 lbs per manual and on my way home the trinary switch has opened from its back spraying the agent all over the underhood. "

If it is the 2 wire freon pressure switch leaking it has been deleted by a TSB and a jumper is placed in the 2 wire connector

With the TSB done the low fans mode ( helps A / C performance ) will be on with initial key rotation

There is an easy paper clip test ( low current ) of your radiator fans as the Fans Control Module brings together the A / C freon load and engine coolant temp commands

 

Ok so on my way to work today i still had the same thing.

car starts. Reading is around 14v.
begin driving and all good.
about half way to work i notice when i stop the volts drop to 13.6.
then getting the same fluctuations.
the needle looks like it goes to almost 13.
and my obd was dropping as low as 13.5v.

when i get home today if the volts are lower when i park i will recheck the alternator voltage.
When i checked alt voltage yesterday i used firewall ground stud.
this time i will try using the alt shell also and see if i get a good reading there.

i am not sure where this loss is.
lights on/off, ac on/off etc and no change.

Only thing that makes sense is battery however i have one battery that is only a year old so should be fine, and currently i have the battery that was in my parts car. And that car reached full voltage.

electrical gremlins are confusing

question.
if i get the car running, then disconnect the battery. And put the multimeter on the two exposed battery terminals. That should give me knowledge of battery or car yeah?
if the battery is at fault i will get the alternator reading of 14.5.
but if the wiring in the car is at fault i will get whatever the lower amount is
correct?