Hello,

Yup, that alternator spark could be the culprit as high energy spark could destroy a condenser.

To test the condenser you'd need a capacitance meter which is may be part of some upmarket/professional voltmeter. If you have a simpler voltmeter like mine (consumer version) they don't have this option (to test capacitance).

And you need to take it out to test it. This also depends on the alternator type. On some old version alternator you may see small metal cylinder or black box (about size of a quarter) located behind the alternator. Newer version like Bosch have its condenser integrated in the rectifier assembly so there's no way to take it out.

In short there's no way to test it. On an old alternator you may replace this condenser with a new part. On newer Bosch you have no option unless you want to replace the entire rectifier assembly.

A much more simpler alternative is just to buy a condenser made for alternator and add it on your alternator. The value is around 250v/0.5 uF. Connect one of its wire to the B+ terminal and the other to alternator's body for ground. Photos of such items as below.







Hope this helps,
Amarin.