On a 93 XJ6 with a Denso alternator, I am experiencing sparking emitting from the alternator only when I rev the motor past 4000RPM or so. The sparks shoot out of the alternator body and a corresponding noise accompanies it. I just installed a new brush holder and a regulator on this alternator. I bought these parts off of ebay as replacement parts which were listed as working for many different cars including the 93 XJ6. So, after finally getting the alternator/battery light on the dash to turn off, I'm am more concerned with the sparking issue. What is going on? Thanks

 

Is it possible that the brush holder is coming into contact with the armature or commutator?

 

Perhaps the new brush holder set is not quite seated correctly. I noticed that the worn brushes, while they still looked okay, had a semi-circular wear pattern as expected. And, the new brushes were flat. Is there a "break-in period" in which the new brushes seat themselves and wear accordingly accompanied by the possibility for sparks at high rpm?

 

I removed the alternator again while I was installing some new coolant hoses. I took it to get tested and it failed - only 10V or so. I had an alternator specialist go through it, new bearings, new rectifier and the shaft was resurfaced. They even cleaned it up and painted it. Upon installation, the voltmeter now reads over 14V as it should and no more sparks. The climate control along with the blowers work as they should along with the radio!!!!!! The gear shift interlock is still an issue however.