Need your help team! I just bought a junked XJ. Runs and drives well but it kills the NEW main battery after only a few hours. Upon opening the boot, there is a low level, but audible, "wine" in the boot. I think it is the controller to the auto start-stop battery. Is it possible, that I have to replace BOTH batteries when one goes bad? Any ideas?

 

jaguarguy, I would be following that whine that you are hearing. I am betting you have a stuck relay or failed pressure sensor for the rear air bag compressor and that is draining the battery. The compressor is there in the trunk too. If you are not sure where the noise is coming from, get a wooden dowel and place one end of the dowel right behind your ear on the hard bone there and the other end on various things inside the trunk. If the noise is louder in 1 spot than another, follow the louder noise. But ,I think when you put the stick on the compressor, you are going to hear it running. Then it is a matter of figuring out why it is running. But, you can atleast pull a plug or something to kill the compressor until you can get a more long term fix.

 

Download the wiring schematics and track down which fuse powers the pump for auto leveling or as you say the start stop controller. Pull the out the fuse and see if it helps

 

Sure, I bet that is it. Where is the pressure sensor located? On the pump? That should be easy to find but of course I'll cut the pump off first to see if it stops the whine. Thanks... Separately, on the battery question, can the smaller battery for the auto "stop/start" kill the main battery?

 

Jaguarguy100, Atleast for a 2012, the compressor fuse is F22 in the rear junction box. The compressor should be relay R10. Pulling either should cause the whine to stop if it is the compressor that is failed. If you want to do a little bit of troubleshooting, let me know. It looks like the pressure sensor is built into the control valve. This would be a simple voltage measurement. It would be between the green wire (Pin 9 - positive) and the white-violet wire (Pin 7 - ground). It should be up around 4 VDC or so (4.0 to 4.8 VDC). If you are getting something less than that, that would be triggering the system to run the compressor. If you are getting that voltage, then I would be looking at the relay and I would say to get a spare and swap that in. If the problem goes away, then the relay was bad. If you don't want to buy a relay just because, you should see 4 wires on the compressor and if you measure for 12 VDC between Pin 2 (green-orange wire - positive) and Pin 1 (black wire - ground), you should get 0 VDC when the car is off. If you are getting 12 VDC (or whatever the battery voltage is), then that would indicate a stuck relay.

Hope this helps.

 

Wow Thermo, now that's a reply! Thanks,....I'll be checking out the system later today. THANKS SO MUCH!

 

Thermo, do you know where I can connect a C-Tek hard wire trickle charger (Called a comfort connector) to the car? In my F-Type, there is a buss panel on the floor of the boot. Keith--

 

Thermo, do you know where I can connect a C-Tek hard wire trickle charger (Called a comfort connector) to the car? In my F-Type, there is a buss panel on the floor of the boot. Keith--

 

jaguarguy100, the ground simply gets bolted to any metal point in the trunk area. You can then take the positive wire and wire a ring lug to any maxi fuse (the battery side post). You need to do it this way to ensure the battery minder in the car knows now much power went in and out. If you don't do it this way, you can throw off the computer and it may not keep the battery at 100% when driving it all the time.

 

So, here is the junction box in the trunk. Should I connect the red (POS) side to ANY buss bar point? Or should I connect the red (POS) to the large battery post that goes to the Big battery or is it enough to connect it to the Start/Stop battery side? In my F-Type, there is a a bus bar and the C-Teck hard wire unit is connected there. Keith--

 

Thanks\. Also, I have placed a new battery in the car and now Jag tells me I need have the car "programmed" for the new battery or ti will overt time "fry" the battery. I ask because I hate to give Jag another $125 to re-program, or is there a way to do it myself?

 

The new battery programming can be done with diag tool, Jaguar SDD, maybe with another diag tools as well? As far i know on pre start/stop models (2010-2012) its not mandatory, the vehicle will re-learn new battery charachters on time. The programming is needed because the charging system is intelligent. It dosent charge battery until its down to XX% level. (XX% is not fixed, it depends different conditions, temp etc..) If battery charging system have been found out that the old battery was so bad condition that it cannont be charged at all (or with very low Amps), it will not charge new battery either before it have been told that there is a new battery mounted, and the system will begin an measurement routine for new battery. There are many cases when batterys and alternators are changed for nothing because of lacking of BMS (BatteryManagmentSystem) programming.

 

Thermo,I have tried to and successfully re-connected the wiring harness to the pump. But now the pump does not go on at all and all the fuses are intact. Can you tell me: 1) Where is the relay for the compressor air lift pump and is there a number in the fuse box for that relay? After the pump ran and ran and ran killing the battery, is it possible that there is another relay closer to the pump? (Maybe on the pump) Without the right height sensor for the car, (Passenger, rear) could that be stopping the pump for actuating? I ask because the old sensor was broken in the accident but the pump was running AFTER the accident also. Weird, right? But maybe it was broken in the "up" pressure position until I removed it from the car. Keith--

 

jaguarguy100, the ability of the compressor to run and a height sensor being broken are 2 completely separate things. I have included a diagram of the air compressor because I think it will help you out with what you are trying to do.

As for your questions, everything that you are after is in the rear fuse box. With that being said, there are 3 fuses you need to check to make sure they are good (F5, F13, and F22). The relay that you are after is relay R10, also in the rear fuse box. Now, while unlikely, it is possible that the ignition relay could be affecting things. So, I would say to check to make sure that with the car on, the Yellow wire with an orange stripe on plug 14A (Pin 20) has 12 VDC applied to it (should be up around 13.7 VDC) and the blue wire with a grey stripe is not grounded when the car is off and grounded when the car is on.

If you know the air system is low on pressure, then you should see the following voltages:
- Green wire with orange stripe running from the fuse box to the compressor (Pin 2 on the compressor): 12 VDC
- Black wire leaving the compressor (pin 1 on the compressor): 0 ohms resistance (anything less than 5 ohms consider good).
- The blue wire with a brown stripe (Pin 6 on connector 14D): 12 VDC
- White wire with a purple (violet) stripe (Pin 7 on connector 14D): 0 VDC (if you measure to ground on resistance, should have a very low resistance, in this case, under 20 ohms is good).
- gray wire with a red stripe (Pin 1 on connector 14D): 12 VDC
- gray wire with a brown stripe (Pin 1 on connector 14B): 12 VDC

If you have all these voltages, then the compressor should be working and would lead me to believe that somehow the compressor to be bad. If you don't get what I say, then let me know which wire(s) did not come out as I said and we can troubleshoot from there.

Diagram for 2012 XJ suspension air compressor, but should be same for 2015

 

Yes don't worry about resetting the battery. It won't cause any problems and in the manual it states the system will auto calibrate over time anyway.
.
.
.