Trying to separate out the charging system warning light from the evap and fuel leak problems that showed up all at the same time. Checked the water level in the battery and 3 cells were low so I added distilled water, Then I did some reading here:
https://www.jaguarforums.com/forum/x...g-57277/page2/

Where I read the following from Thermo:
Pin 1 (generator control signal), Red/green wire
Pin 2 (power from fuse box to power the regulator/field), Green/red wire. Should be at the same voltage as you see across the battery. If you have more than a 0.2 VDC difference, you have an issue with the wire or the fuse itself.
Pin 3 (Field control), orange/green wire. This will fluctuate to maintain the output of the alternator at the desired voltage. As long as this voltage is not 0 VDC or battery voltage (12 ish volts), then it is good.

In another post it was suggested to measure voltage at the main lug on the alternator. I did this and I get:


During the 5 minutes I ran the car the charging system malfunction light went out. It looks to me like power from the fuse box to the field might be a problem, it is nearly a volt lower than battery voltage but should be the same, correct?

 

Ringing out the cables, from Fuse 6 in the engine bay fuse box to junction JB1 I get 1 Ohm resistance. The fuse itself measures 0.2 Ohms, the same thing I get when I just touch the meter leads together. From JB1 to the alternator pin 2 I measure 16 Ohms. Pushing and pulling on wiring harnesses changes nothing so it seems the resistance is probably in the connector itself. Now if I could figure out how to disconnect that 4 pin connector on the alternator without removing the engine from the car...

 

dh53, with what you are showing, that all seems fairly normal. The 2 things that do make me question things is how you measured voltage at the "large lug". The red lead should have been on the big lug, the black lead should have been to the body of the car. This should have given you something slightly higher than what you see at the battery. I am not sure how you got the voltages that you got. The second thing that has me concerned is the voltage drop across the green/red wire. Under a heavy draw on the alternator (Engine on for less than 30 seconds) is telling me that the wire is pretty much at its rated capacity (standard wiring does not allow for more than a 1.0 VDC drop end to end of a wire at its rated current value). As for this being lower, I would expect some drop as this is seen on every wire that flows any amount of current. But, like I said, there are limits. As long as the field control (orange/green wire) is not at/close to battery voltage, then you have some room for the alternator to output more power. So, while not ideal, I would call all of this good. The only value I would like to know is the output of the alternator as compared to the voltage on the battery. Again, that cable (even though it is in multiple pieces), should only drop 1.0 VDC from the alternator to the positive terminal of the battery. But, based on the voltages at the battery, I think you will find that these are going to be close to the battery voltage.

 

I measured all voltages directly to the negative battery terminal. For instance the large lug voltage I have one meter probe on that lug at the alternator and the other is on the negative battery terminal. For the voltages at the 4 pin connector I have sewing needles slid in at the connector. I tried pushing and pulling on the needles wondering if my 16 Ohms is just due to my measurement pin not having great contact but moving that pin did not change the resistance reading on my meter at all.

I didn't look up the AWG but these look like 20 to 25 AWG wires. At about 1 meter in length the resistance should be far less than 0.5 Ohm. If the AWG is larger (meaning thinner wires) and/or the distance is a couple of meters, I still expect to measure less than 1 Ohm so 16 Ohms seems like a lot.

On the other hand, after 5 minutes running the engine and then shutting it off the battery voltage was higher than when I started. Isn't this by definition the charging system working?

 

Hi dh53,
I think what Thermo is puzzled with is the voltages you are seeing at the big lug on the alternator, as that wire more or less ties back to the battery positive terminal via the starter motor B+ supply cable.
Therefore it should always be at least reading the same as your battery voltage. It shouldn't give you readings of 2.4V, 1.6v and 0.8v as written in your testing table.
Something is amiss there with either the cable or a testing anomaly.

The 16 ohms you are reading from JB1 (pin 13 I assume) to pin 2 of Alternator plug EN49 sounds very odd.
It should be a direct wire (no splices), so should have a low end to end resistance.

You sound like you are using a digital multi-meter, which are great and pretty darn accurate.....unless you are reading ohms on a live circuit.
If the cable you are trying to measure still has power on it, if there is any existing voltage drop across that cable and you try to measure the resistance with metre of that cable, you will get false readings.
The multi-meter is apply its own voltage across the "measured target", which it then interprets that voltage as a resistance to be displayed. If you have any other stray voltages present across the target, then the multi-meter (which is a high impedance measuring tool) will have its measurement result corrupted.
Disconnect the car battery briefly to remeasure that JB1 to alternator pin 2 wire and see if you are still getting 16 ohms, if so, then that wire appears to have a problem.

 

Agree, I was shocked that the lug on the alternator was not exactly the same as the battery voltage as it seems to me there is an AWG 0 or 2, a big piece of copper from battery + to that lug. Will try again tomorrow. It isn't straightforward to clip on to that terminal without some miniature hands getting in there but I will try.

Yes, using a Fluke digital multimeter. The 16 Ohms I measure between fuse and alternator was with the battery negative disconnected. I will disconnect battery + and measure again.

 

If you already had the earth to battery disconnected during your prior measurements, then there should be no relative voltage on the cable to upset the Fluke meter. No need to repeat that measurement.
Hard to go past a Fluke for accuracy and dependability......Good choice there BTW!

Logically if you are measuring between the fuse F6 contacts through to the alternator plug EN46 pin 2, then you are also incorporating the connectors JB202-1 (Fuse box connector) and also JB1-13 into the consolidate wire result.
If you are using a pin to pierce the cable insulation to get some readings, intercept the Green/Red wire leaving JB1-1 so you can do your ohms reading upstream to F6 again and then from the pin downstream to EN49-2.
If the high resistance is in the upstream reading then you likely have a connector with problematic resistance inside JB202-1 or JB1-13.
If however the resistance is downstream, you likely have a fractured wire from JB1-1 to EN46-2 or a corroded/tarnished connection inside the plug EN49 on pin 2.

 

I tried piercing the insulation to see if I could divide and conquer the high resistance but I got nowhere. Eventually threw in the towel on finding the problem and ran a new wire from JB1 pin 13, which I know is solid to the fuse box, to the alternator pin 2 of the 4 pin connector. That way the lucky person diagnosing problems on this car in the future won't have wires bypassing connectors they are supposed to be in. Soldered the new wire in, heat shrinked the splices, then I measured about 0.8 Ohms from fuse box to alternator pin 2.

Before starting new voltage measurements I looked very carefully at where I thought I was connecting to the main alternator lug and found I had wrapped my test lead around the insulator next to the big copper lug, I'm not sure why I measured any voltage at all at that lug yesterday, We'll call it pilot error and move on.

Today when I measure voltage with the engine running I get alternator connector EN49 pin 2 = alternator main lug = battery voltage. Charging system malfunction light is out. Awesome, now I can concentrate on the fuel rail leak, the evap leak codes, and the high fuel rail pressure code.

Edit to add: all of my voltage measurements are voltage relative to the negative battery terminal. My multimeter ground/common lead was clamped to the negative battery terminal.

 

Hi dh53,
If you have kept all the connectors intact and just spliced in a new wire onto 'Pigtails' you have created of the old Green/Red wire ends, then you must have had a section of that original wire that had become internally fractured through all of its individual strands.
Likely that vibration has worked away at a nearby securing point flexing the cable until it mostly failed.
Well done sticking with it though....hats off to you!
Yep ...over pressure and evap next.
I saw the comment posted on your other thread about possible heat related fuel expansion in the line since you put in that non-return valve.......certainly plausible, especially if the new non return valve is efficient and you only see the effect if you get some decent heat into the engine before switching off and then restart again prior to everything cooling right down again under the hood.
In that scenario you could see high rail pressure error when you are about to restart the car, but as soon as injectors start to operate that pressure will return to the normal systems regulated state.

 

Mark, It could be as you say, vibration & rubbing caused a failure in the wires. Could be mice. They have caused me a couple of electrical problems in the last 3 years. Part of my "parts shotgun" this time is peppermint oil which is supposed to keep them away. Previous experience with the mice is they chew through the wire so the wire works or it doesn't, no high resistance problems before.

Regarding high fuel pressure, pressure at the rail and with the inline check valve in place decays from about 54 psi at engine off down to 35 psi in about 1 minute. I am wondering if my high fuel pressure is as you mention restarting the car "too soon", as in the pressure is still up near 50 psi and I restart the car so the pump comes on to prime the system regardless of existing pressure. The solution is to not restart the car for at least 1 or 2 minutes since it was last shut down. That explains why for weeks of normal operation I didn't get the high fuel rail problem because I would never restart the car that quickly. The high fuel pressure and charging system problems appeared at the same time because I am restarting the car so quickly while diagnosing the charging, not because of some underlying problem caused them both. One hypothesis, probably better placed in the other thread.

 

Roger that....was just trying to nail two birds with one stone....

We don't seem to get too much in the way of problems with mice and rats chewing through car wiring here. Backs of stoves and ovens is however a totally different thing!
We do get mice entering wall and ceiling cavities particularly in rural houses as we head into winter (seeking the warmth) and they certainly can create some significant carnage to house wiring, data cabling and insulation.

When we had the large 2010 earthquake here and the city centre was totally cordoned off for over 6 months, rats took over the centre city and a massive population explosion ensued as they got into all the food stocks of the restaurants and cafes' before the damaged buildings were rendered safe and gradual cleanup or demolition could begin. Talking to police and army personnel that were patrolling the inner city at that time, they would say the ground appeared to shift with the massive hoards of rats that were moving around at the time.

Now if you want to see what can really screw up your car.....take at look at the native Mountain Parrot we have here....the Kea.
Incredibly intelligent, strong and inquisitive, a lovely but destructive unique native bird.
They can create thousands of dollars of damage to a car in minutes.