My '06 2.2 TD x-type just started to show the battery light on the dash. Measured battery voltage at 12.22 volts, engine off. Started up and measured again. 12.15 and falling. New battery was fitted in April, new alternator in June. Checked and cleaned battery connections, cleaned and remade ground cable connection. No change.
When changing the alternator, I tested and inspected the positive cable to the battery, all seemed ok, and it was charging ok at 14.4volts. Appears to be a fault with the request line from ECU. How do I test it?

 

Check F36 (7.5A in Diesel model) in power distribution fuse box for failure.
Supplies 12V to alternator internal control.

 

Thanks. I'll check it in the morning. What could cause that fuse to fail?

 

Terrazen, age is the most likely cause. Yes, as silly as this may sound, fuses do "wear out". As you pull current through a fuse, it will slowly burn itself out when you are pulling near the limit of the fuse. So, after a long time of being near a limit, it will fail because what is left o the fuse is now a lower limit and you hit that limit. If you install a new fuse and that one blows, then I would start worrying.

 

Well I checked the fuse, F36 in the power box (under the bonnet, near the battery) and it's ok. Battery positive voltage both ends. Fuse looks ok and tests good on multimeter. I guess the next step is to check the alternator's multiplug. But I'll wait for the rain to stop. (No garage)

 

You mentioned that you checked the battery ground connection. But did you check the alternator ground connection?
Also: Checking any connection in just "one moment in time" could be deceiving, if you are dealing with a loose/unreliable/corroded connection.
You may have contact in one moment, but not the next...

 

When I said I checked it, I meant I took it off, cleaned and abraded the lug and the body around the fixing point, wire brushed the bolt and put it back. Did the same with the battery connectors. That definitely isn't the fault I'm looking for.

 

Terrazen, unlike other versions of the X-Type, the diesel alternator does not have a feed from the ECU. It regulates by measuring the internal voltage. Atleast that is how it appears to do things via the drawings. So, as long as you have 12 VDC+ going into the alternator on Pin 2 (green wire with a red stripe), then your alternator is getting the power it needs to power the field. I would then move the lead over to the large cable coming off the alternator to see what the voltage is there. If you have say 15+ VDC there with the engine running, but only 12 VDC at the battery, then you have a cable issue. IF the large terminal on the alternator matches what is at the battery, then you have confirmed a bad alternator.

 

Well, that's it. I have a faulty alternator.
I set to this morning to get it sorted.
Yesterday, I had downloaded the factory wiring manual. 194 pages of it. Printed off all the relevant pages, pin assignations, wire colours, everything.
I checked the continuity of the main cable, having disconnected both ends, alternator to battery. It is less than 0.5 ohms. So that's ok. Removed the 3-pin plug from the alternator and checked for continuity of each wire, brown, white and orange/yellow. ( the manual says it's green/red but mine isn't.) They all check out ok. Checked the ground connection, alternator to battery negative, it's ok, less than 1 ohm. Started the engine, with the 3-pin alternator plug disconnected and checked to find battery voltage on the orange/yellow wire. Made up a link wire to connect just that wire through to the alternator, and started it up. Still not charging. Is there anything more I can do? Or am I right in the conclusion that my 6-month old alternator has failed? It has a 12 month guarantee, so I can get it replaced, but it's a major pain to remove and refit and I wish I didn't have to do that all over again!

 

Terrazen, the check that I would do is to leave the plug connected to the alternator for the power. But, this is time, take a pin and attach a wire to it (if needed) and what you want to do is start the car and then measure from that pin to chassis ground (using the wire as an extension because I do not recall how much room there is with the plug installed. See if you are getting 12 VDC or if you are getting say only 5 VDC. The issue with power wiring is that most of it normally has some significant amps running through it and even a small resistance like 1 or 2 ohms can reek havoc. For example, you have 12 VDC coming off of the battery feeding the power to the alternator. Even having a 1 ohm resistance in that wiring (pretty hard for your multimeter to detect), that would drop the voltage the alternator is seeing from 12 VDC to 2 VDC with a 10 amp draw. 2VDC would make the alternator output nothing. hence why I say to check it while connected. It is a bit more telling than just normal checks. That is why I would also recommend checking the alternator output with the car running. With the alternator capable of outputting up to 130 amps, even a fraction of an ohm can cause major voltage losses.

 

Which wire is it you want me to check? Output or reference voltage?

 

Terrazen, you are looking to check the voltage at the plug with it attached to the alternator on Pin 2 (green wire with a red stripe). You are going to most likely need to slide a pin down along side the wire to get past the seal on the end. Then keep pushing it in until you feel it hit something solid. That should be the metal inside where the wire attaches to the pin.

 

Thanks, Thermo. I did that. (The wire is yellow/orange on mine, for some reason) and found it to be at battery voltage, as it should be. I've ordered a repair loom from eBay, about 18 inches long, it's meant for a transit connect, but it's the same charge system. Just to be on the safe side. I've also ordered a new OEM standard alternator. When I get the old one off, I'll get it repaired under warranty so I have a spare. I don't need the car standing on the driveway with a wheel off for several days while I wait for the repaired one to come back. I'm positive that the alternator is faulty, though what the fault is, I can't tell. May be the clutch pulley but I won't know until it comes off the car. In the meantime, I can still use the car, I just have to charge the battery every couple days. What a PITA!

 

Well, make sure to charge the battery plenty, better every day. Plus, do not drive too far and not at night!
Many many decades ago I had to drive the car of a friend back on the Autobahn quite a distance in the night, as I was the only one sober - and that car had such an issue.
I had too choose, if I drive without engine or without light on the Autobahn, as there was not sufficient juice left in the battery for both (spark plugs need power).
Luckily it was that late that there was very little traffic, but when I saw a car approaching from the rear I had to switch on the lights shortly before they would have hit us and with the lights on the engine was sputtering...

 

Hi, Peter. My new alternator arrived this morning. It's an rtx, which was an OEM supplier, so it should be ok. Now I just need to wait for the rain to go away and I can fit it. Only thing with it is, it has a solid pulley and I think I'd like to put an overrunning pulley on it. I've been using the car around town, charging the battery each night and it's been fine. As it's a diesel, it draws little current when running, (no sparks to make) so the battery holds up well. So, wish me fair weather, and I'll update the thread when I'm done.

 

Well then: Wish you fair winds and following seas...

I just learned something in your post: "the overrunning pulley" - explained here:

I did not know about that. What's does the X-Type use as OE part?

 

Well, that's it done.
fitted the new alternator, did it by removing the turbo heat shield and the fuel filter and bracket, that way, the alternator is accessible from above, no need to remove the wheel, inner wheel arch cover or split any joints. I could do it that way, since I had fitted a new belt when the last alternator went in. Had to take the top engine mount off to get my tensioner tool in, ( that's a right game in itself! Whoever heard of 18mm nuts! )and a trolley jack with a piece of thick ply under the sump to control engine height. Got it done. Had a bit of fun bleeding the fuel feed, air lock due to the filter coming out, but that's ok now. Then, monitoring the battery voltage, it started out at 12.8 volts, but after a couple minutes, went up to 18.6 volts! Had no indicators, climate control or electric windows, but battery light was off and the airbag light was on. Then the ecu light came on.
Fault read as "System Voltage Fault". I'd fitted a replacement alternator control cable from eBay, it was a Transit Connect item but electrically identical. Tried the old one and got the same result. So I took it off again. The battery is now getting 13.6 volts at idle, going up to 14.4 at 3000 rpm. I can live with that for now, but I'll be in touch with the supplier tomorrow because my battery light comes on with that cable off. I'd be happy if I had a silver battery, but I didn't know about them until this fault appeared, so I'd fitted a lead-acid one and I don't want to cook it. What a pain!

 

Here we have batteries sold under the names "SuperCharge SilverPlus" and "SuperCharge GoldPlus"... - in case that is what you are referring to with silver battery. Those are the batteries, which I use.

Well, I heard of 18mm bolts and nuts. I just build a carport with dozens of those.

I don't quite understand, what you write about 18.6V and the resulting various faults. Is it all good now? 14.4V charge sounds OK...
So apart from the battery light being on, all is good now and the battery is being charged OK?

 

Peter,
Yes it's all good now. But before I go into it, you asked about silver batteries. I'll tell you what I've learned.
In 1997 Ford introduced a 'new' battery technology to be introduced throughout their range. They called it "Silver-Calcium". It's basically a development of the old lead-acid battery but with a small amount of silver and calcium in the matrix. This makes the plates stronger, less prone to overheating and to cold weather, and increases their current output by about 10%. It also means that to be fully charged, they need a slightly higher charge voltage of about 18V. All Ford-produced cars, including Jaguar models, were equipped with a "smart charge" system, which produces up to the maximum 18V shortly after start-up (depending on battery condition, outside temperature and engine temperature) to give the battery a "wakey-wakey" boost charge, to replace the charge expended in starting, before dropping to what is essentially a maintaining charge when the engine is warmed up.
All this malarkey is handled by the ECU, hence the three-wire alternator control loom. If this control loom is removed or otherwise compromised, the alternator automatically goes into default mode and behaves like a standard 'dumb' alternator. The worry I was having is that if you put a standard lead-acid battery on the car, it will overheat under the 18volt 'overcharge', damaging the plates. I had thought my battery was the old standard type. But I checked it this morning and it is indeed, a Silver-Calcium one, so I've put the control loom back on and everything is now tickety-boo. The charge voltage went to 17.6 for a few minutes after I started up, then dropped to 13.7. So we're all good!
As to the overrunning/freewheeling alternator pulley, I believe Jaguar used an SGR one but I can't be sure. I stuck with the solid pulley that the alternator came with as my mate who used to run a garage said they're more trouble than they're worth. Great when they work but you have to get the alternator off the car to change the pulley, and they do fail. Regularly, according to my mate.
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Ok, thanks, learned something again. I did not know about silver-calcium batteries and their secret.
I checked: The SilverPlus battery, which I mentioned above, is a battery with lead-calcium plated plates - no silver in there.
The GoldPlus Battery is a battery with a thicker layer of lead-calcium on the plates - no silver nor gold in there.
Should I need a new battery again (mine last very long, as I permanently recharge them with CTEK battery chargers), I'll check, what a silver-calcium battery costs here...