Hi there!!
I had a great troublesome time having a floor board bought from Ebay since it came with a failed or non-working wah pedal.
I checked everywhere for a solution but nothing fitted. The pedal activated the wah function excellently, but the sound didn't go up and down as a wah was expected but just remained stuck at the high modulation, as if the pedal were being stepped on and nothing else.
Later on, I had the pedals circuit board taken out and had their components measured with an electronic tester by a friend of mine. And what was found??
Since the only faulty thing on the floor board was the wah pedal function, not the volume one that was ok BTW, it was evident that one of those little components on the wah side was very dead !and so it was!:
Which one?
THIS TINY THING: 2N4401 transistor
Remove the broken one, solder it and... Long Live your WAH again!!!
Hope it work for you guys as it id for me!!! May God bless you all!!