On start up my 95 V12 shows almost 14 volts but when warmed up it goes down to a little over 13. When lights or AC turned it goes down even further. I have been told on other forums that this is normal but on my 96 XJ6 the gauge stays at around 14 volts at all times even when AC and lights are on. What does the gauge reading look like on any ones gauge that has a 95 V12. I am checking the volts at the battery with a meter so I know they are correct. The gauge will go up occasionaly to a liottle over 13 with the AC runnijg but not often. On start uo every time it is arould 14 like the battery has been drawn down the previous trip. I may not have a problem but it sure looks strange to me. I replaced the alternator this spring even though the alternator shop said the alternator was fine but no change. Please help me so I can get this resolved if it is a problem. Car has never let me down but ocasionaly it drags on start up after driving a while. I replace the battery this spring also.

 

Sooooo, I am assuming that the DVM across the battery is reading the same as the dash gauge?????.

If that is so, then the gauge is OK, the system is NOT.

Not real familiar with the 6ltr set up, BUT, on the earlier cars the earth strap fiasco around the LH engine mount was a real PITA, as was the earth strap bundle alongside the battery in the boot.

On the other hand, if the DVM is reading higher (about normal as expected) than the instrument gauge, then the issue is within the dash pack, and/or the signal to it, and that is where I am flying blind on that year car. Yours may be the same??.

My X300 XJ6 is as the other car you already mentioned.

Our XJ-S is always at 14.1v no matter what is running, but I reckon the 115amp alternator upgrade has a lot to do with that. The early XJ-S dash gauges (barrel gauges) were vague at best, but mine reads "almost" the same as my DVM now, so all OK.

 

I do not think your system sounds as though there is anything too wrong. On my car (all electrics cleaned, all earths 100% OK) my plug-in digital thing reads 14.1/14.2 on start upi with aircon running and small fan therefore running. If the big fan (pulls 17 amps) comes on and the interior aircon high-speed fan too, then the digital gauge drops to about 13.4/13.3.

I have Grant's 115 amp mod. before, the thing would marginally discharge under these conditions.

Greg

 

I'll get a bit technical here.A lead acid battery is 2.1volts per cell and a 12volt battery is 6 cells so fully charged your battery should read about 12.6volts with nothing connected to the terminals. And remember your DVM depending on the model could read as much as ±1.0volt from nominal.What is happening in your case is that your alternator is outputting a larger voltage because your battery is not fully charged. As the battery comes up to full charge the voltage the alternator puts out will drop, otherwise the battery would ovecharge and explode.The other variable is - as you switch on more stuff, fans lights etc they draw more current and this will also cause the voltage to drop. Unless you are having an issue with the battery going flat when not driving I do not think you have a problem.

 

ive got an alternator for sale.