Hello all,

My XJ has been a wonderful car for me so far into my ownership. I have put about 20,000 miles on it in 2 years for a total of 108,000 miles. I have done the regular maintenance (including transmission filter) and replaced the leaky transmission lines, battery, tires, rear air shocks and that's about it.

The other day I was driving and my battery light came on. I checked the voltage with a multi meter at the battery and only saw 11.5 volts at idle. I have sense parked the car until I can figure it out. I assume the alternator went bad. The previous owner replaced the alternator with a non-OE part at 57k miles.

Is there anything else I should check before replacing the alternator? The battery is only a few months old.

Any input it appreciated

 

Most probably the alternator is causing the problem. But to rule out other possible issues it is recommended to measure the charging current directly at the output of the alternator. On the V8s this is a green/orange cable on pin 2 of the black four-pin connector on the alternator, measured against ground at idle, should be at least 14 V.

Fritz

 

Yeah, I can think of one. If it were me, I would check those battery terminal connections; make sure that they're clean and snug.

 

Was the car running when you checked the voltage?

 

The OP wrote that the battery measured 11.5 VDC at idle (meaning the car was running).

 

Sorry i sure missed it

 

Thank you for the advice all good points.

Another thing I have noticed when I start the car cold, the battery light comes on after about 30 seconds after start up and the cooling fan runs at what sounds like it’s highest speed. Kind of strange that it does this. I don’t remember hearing the cooling fan when the engine is cold before.

anyways going to try and put a new alternator in it soon.

 

There is something that I would also like to bring up here. I mean, one just can't take for granted that the alternator is indeed at fault as some of the control signals to the alternator may not be present. In fact, to be on the safe side, it may be advisable to bring that alternator to an alternator repair shop to have that alternator checked out first.

 

I replaced the alternator and now all is well. The car is charging great. It was not an easy job, had to support the engine, remove the passenger side motor mount to make space to R&R it. The bottom stud on the motor mount broke in the process, had to replace the mount as well along with a new serpentine belt. Once I got everything back together the coolant reservoir tank sprung a leak....changed that tonight and all seems very happy, back on the road!