Low speed on pump 2 not working

[HL5]

Wonder if anyone can help please?

I have replaced pump 2 in my beachcomber hot tub (Balboa control pack). It is a functioning two speed pump, yet it won’t switch on in low speed. 

I have swapped pump 1 and 2 over and both work at both speeds where pump 1 plugs in, but neither work at low speed where pump 2 plugs in. I can hear the relay click when pressing the control panel once but the pump does not come on, pressing it for a second time switches it on at high speed. I’ve also changed the circuit board in case it was anything there (had a working spare) but the issue remains.

Any ideas how to sort this? 

[Spa Board Doctor]

Post a picture of the wiring schematic that is printed on the inside of the enclosure cover for the board.

[HL5]

Thanks for taking a look

[Spa Board Doctor]

It seems like there must either be a bad fuse, bad relay, or burned up trace on the board.  This doesn't explain why your spare board didn't solve the issue.  Weird.