I've tried this but my problem is so intermittent that it is difficult to identify the problem. I swopped channels on my amp and still the same door speaker was affected, so I know it is the wiring to the crossover (unlikely), the crossover itself (replaced all capacitors recently), the wiring to the tweeter (possible - I've taped up the little amount of exposed metal on the spade connectors) or the tweeter itself.

EDIT: and I also tried swopping tweeters and the problem remained with the same door panel - so wiring/crossover the only remaining potentially faulty elements.

 

Is it possible to swap the crossover, or swap the channel it uses on the crossover - Right to Left.

Then you will know for sure whether its the run or the cross over.

NB dont check a circuit with a crossover connected, it should be open circuit across terminals on a typical crossover.

 

I had this, pop the door card off and have a look at the speaker. (Mine's a JDM BTW).

The speaker terminal had rusted causing the fault so I upgraded the speakers.