What is this part? Front right of engine bay between battery box and radiator. I have the dreaded not charging light on, changed alternator after checking and getting 11.2 out between output post and negative battery terminal and engine bay ground. Leads are checked out ok, same issue with new alternator, both batteries I have for this car are tested good, with high CCA. The 4 pin plug to the alternator is clean. Is this in the charging/regulator circuit?

 

The piece in the photo is the fan control module. I am sure someone with more experience will jump in but it sounds more like a bad grounding issue.

 

The box in the photo is the Fan Control Module. As for the charging problem that you're having one of the more common causes are the battery cables.

You may want to read this

https://www.jaguarforums.com/forum/x...-issue-244109/

My personal experience

https://www.jaguarforums.com/forum/x...-cable-245499/

 

Carl, based on your initial voltage, I would venture to guess you have a bad ground on the car. I would start with using a multimeter and measuring between the lead part of the negative battery terminal and any metal point on the engine when you have a large electrical load on the car (headlights, both seat heaters, rear defroster, dash fan on high). If you are getting over 0.6 VDC on this measurement. then you have a bad cable or two, or three.

If this is good, then I would measure across the battery terminals (to the lead part only). and see if you are getting something over 12.6 VDC. If yes. then your problem is inside the passenger compartment, not the car itself. If this is the case, then odds are, you are looking at a bad fuse box in the engine bay. If you are not getting 12.6 VDC across the battery, then I would be looking at the wiring between the alternator and the starter. We have been seeing more and more issues with the leads on the starter corroding, leading to a low voltage condition.

For your car to have 11.2 VDC, you either have a battery that is not fully charged that is keeping a car running with a decent electrical load or you have a very large electrical load on the car. As a general rule of thumb, 10 amps will drop the battery voltage 0.1 VDC. So, to have a 1.4 VDC drop (from 12.6 to 11.2), you would have a minimum of a 130-140 amp draw on the electrical system. Seems a bit excessive for this time of year.

 

ok chaps, ignore the fan control module, and having read nearly all @Thermo 's alternator and charging diagnostic posts I was battling with this issue.

Long story short, diagnosis was inconclusive at this point but appears to have resolved. The last thing I did was Gerry-rig a 1 gauge lead from alternator - starter motor - battery positive terminal. I have ordered both Jag positive and negative leads to swap out on spec tomorrow.

What I found and did to this point.

• Battery light on, car draining battery, not starting, not charging. Oddities in the car like stereo amplifier not working so sound coming out tinny, AC and climate control flickering, no codes relating to charging came up on ODB2 though.
• I have 2 batteries for this car (one spare and one in use), both fully charged for diagnostics - both tested with commercial load meter fine
• New serpentine belt fitted as old one was down a V rib!
• Prior to changing anything the alternator output checked at 11.2v between alternator output post, starter post and battery post and chassis/engine ground points
• Changed alternator to NAPA 100A refurbished unit (eco friendly AC charge vented to atmosphere)
  • same problem existed with new alternator and same 11.2v tested
• , Removed leads, resistance checked from ends at 0.4 Ohms, and cleaned all connections and mount points for both positive and negative
  • with no change in results
• Yesterday afternoon I swapped the positive lead from alternator - starter - battery post with a 1 gauge that I mustered up
  • Well, last night it had the same no charging problem! So I took the motorbike out for some wind therapy and to ponder "life, the jagiverse and everything".
• Woke up to find these posts (and very much appreciated everyone)
• My next step was to check the 4 pin ECM control/communication wire integrity however...
• The car started, no battery light on and test run 30 mins on highway/motorway

Note, we've had a heatwave and alternator appeared to be running extremely hot to the point of almost burning hand, its cooler this morning which may (or may not) be partisan to the problem. Will monitor and update but everything one needs to do to diagnose this issue is already covered by @Thermo and the plethora of other more knowledgeable and helpful members.

At least I can remove the alternator main power lead in about 10 mins from above now, air filter and air box out, battery and battery tray out, 18" long 3/8" drive extension with socket does it for me. lol

 

Carlstev, Once you get a 100% solution to this, I would put the factory alternator back on and see if you are having issues. I say this for 2 reasons: 1) (the bigger one in my mind) is that you are dropping from a 140 amp alternator to a 100 amp unit. So, especially during the winter, you may find that you are not going to have the power that you need to run the seat heaters, dash fan, lights, and rear defroster (these alone take you up over 100 amps), 2) experience on this site has shown that aftermarket alternators in general do not last long in these cars if they work at all. So, just keep that in mind. You may ponder taking the alternator to a DC refurbishment place and have them give the unit a once over. But, based on what you are seeing, all they may do is blow some dust out of the unit, replace the brushes and give it back to you.