You're new here, so will be forgiven this serious breach of forum protocol.

1) There's no need to point out how wonderful I am. It's just a given around here. Think of the bandwidth that would be tied up.

2) Complimenting me causes my head to swell up. In severe cases, I'm trapped in the house because I can't fit through a standard doorway. I have to get my wife to bring me back down to size. Luckily, she keeps extensive mental notes and is always ready to assist.

 

Ah but if your trapped inside that can only help us right as you've more time to offer us poor souls advice...

 

your climate control is definitely dragging your system into the dirt. Every time you have the climate control On, youre way below charging voltage. The 12.8 V you got with the radio and headlights on is probably low only because you drag the battery down in the prior step with the climate control on I bet you if you did that again and let it sit there with climate control off it would come back up to 13.4 eventually

 

I agree with you, Im charging the new battery on trickle charge and once its fully charged I will do the tests again but I do suspect the CC is the culpret. Thanks greatly gor your input, its been so weird how its behaved.

I understand that tests need to be done on a full battery my my thought was if the alternator was shot it wouldnt have gone higher whem engine turned on, in fact the oppostie?

 

I was wondering the same thing, but something doesn’t add up. The HVAC system has a 10 amp fuse. If something downstream of that fuse was drawing too much current, the fuse should blow. Even if the circuit was drawing 9.9 amps, the charging system should be able to handle that.

For giggles, pull the fuse and see if the situation improves. For a post-facelift car (2003+), it’s fuse F32 at the Front Power Distribution Box:

 

Thanks will try that, new battery is fully charged and is reading 13.51 of the car

 

New Battery on car 13.23
Engine on 14.37-14.40
Radio on 13.82
CC on 12.91
All off 13.88 but it was rising for sure which indicates its charging?

Im not convinced new battery is all that great, will do tests again in a hour with that fuse out

Fuse out new battery

On car 13.10
engine on 14.28
radio on 14.34
radio off 13.86
CC on 13.20
All off 13.84
CC and radio on 13.06 dropped to 12.99 over a couple of mins
All off 13.82
Engine off 13.22

Not sure if im reading this right it seems the new battery is disapating when engine not on, seems alternator is ok but he ac is causing drama?

 

The alternator definitely looks OK. You’re getting great voltages as it’s charging. 13.2 with the climate control on seems low but I haven’t necessarily check my voltages with that exact situation. once I have my car back I can make the same measurements and you can compare but my wife has it right now.

To check if you have a current draw with everything turned off measure the battery voltage after turning off your car and wait an hour or two or more And keep re-checking the voltage without ever changing anything. leave your trunk open so the trunk light turns off and don’t open any doors just let it sit and just measure the voltage periodically and check it over time.

batteries have a crazy behavior where if you put the high current demand on it by starting the car it will kind of drag your battery down and if you turn your car off immediately after starting it the voltage will seem low but over the next half hour hour or so it will go up a bit. I always called it a space charge because it seems like it comes from outer space. But for all I know is a term somebody told me when I was young and it stuck but who knows.

So check the voltage with everything off overtime and see if the battery continues to go down into the dirt. if it does then you start pulling fuses and relays to see which fuse its related too.

Charge the battery up pull the fuse for the climate control check the voltage with the car off. measure it over time see if it discharges at the same rate. Eventually you’ll pull the fuse or relay that tells you the culprit.

One important thing to do first is make sure your battery connections are clean and tight. No corrosion at all. Shiny battery post and battery terminals. Cables snugged up to the terminals on the battery. make sure your ground connections are not corroded or rusted. Make sure the connections to your alternator are on tight and not loose make sure your alternator belts not loose.

Corrosion on a terminal causes resistance and resistance will cause low charging situation and it will also heat up the terminal causing it to loosen over time as it expands and contracts with the heat. Good luck I love fixing electrical stuff when it’s finally solved I feel so accomplished and successful.

 

diesel has an internally regulated alternator like the v8 it should be in the high 13s low 14s no matter what.

it looks for average charge over set period of time being above 13.9v and on the denso ecm cars it eventually logs a p1632. put an amp clamp on it and find the max output

 

daft question im sure, where would I put amp clamp on it?

 

Im happy the alternator is ok to be honest, I did pull the fuse you suggested which was on the ac right? as the passenger side stopped blowing cold the drivers never does but I think the valve might be a issue there.

 

main cable to the alternator put all the loads on

 

my bad the diesel has a field monitor and a control circuit but it doesn’t work the same as the gas v6.

good luck

 

I need to apologize in advance for the following mental image, to be forever stuck in everybody's brain:

Got to thinking during my morning shower. While toweling myself dry, I had an epiphany. Was the engine RPM constant for these voltage checks?

I'm wondering if the HVAC variation is a red herring. Perhaps with the AC on, the engine RPM drops slightly. Alternator output is already marginal at idle, so you might see a more pronounced drop with the AC running. Throw in an increased electrical load from the AC clutch, and that might explain at least part of the situation.

My latest thoughts, subject to wind direction and my medication levels, is to repeat the test but hold the RPM steady at 1500 or so to rule out any variables.

 

It seemed to be but can do again for sure... hey ive a great sense of humor so your all good. Are you saying it possibly could be the Ac thats causing all of this?

 

The term is recovery effect. It's most pronounced in a lead-acid battery.

It has to do with the thickness of the plates and the interaction with the electrolyte. A short fast discharge (such as an engine start attempt) takes the readily accessible "power" on the surface of the plates. Let things rest so the chemical reaction can equalize for a few minutes, and the "power" from inside the plates enters the room, so to speak.

You're not gaining any overall power. It's merely existing power being redistributed where it can be used.

 

I'm mostly thinking out loud, wondering if our test procedures are leading us astray. Not sure about Jaguar's official method, but usually you hold RPM around 1500 for a definitive test of alternator output. Most alternators do not put out full current at idle speed.

 

So do the test at 1500 RPM?

 

Yes.

 

with that fuse that was suggested removed in or out?