Blower doesn't work on High....(opposite of usual)

So I am lost...

I completely rewired the whole HVAC system with heavy gauge power cable and 40amp relays.

I know it is common to have the resistor pack go out and the blower will only work on high (bypassing the resistor pack)

But mine developed the opposite problem today, it works on all settings except high. Sometimes high will come on, but it will cut out. All other speeds work fine.

Could it be the actual control box? (Like, the blower speed switch itself?)

mine hasn't worked all winter, only on lower speeds, looked for high speed relay in fsm, didn't see one, I'm assuming it's my switch and was waiting for warmer weather to pull one from junkyard. Sure sounds like you got same probs.