2 speed wiper motor - only 1 speed

Hi everyone hoping to bounce a few ideas off anyone reading this.

I have been helping my brother get his 71 Duster sorted out so he can get it saftied amd get it on the road.

We have been trying to figure out the deal with the wipers.

It is a 2 speed motor, and he has the proper 2 speed switch. But he is only getting 1 speed (high). Not low, and the high speed it quite slow. I am wondering if the motor is the issue? Or potentially the ballast that the black wires go to?

On high, we are getting power at the red wire and blue (accessory).

Anyone experienced a similar issue?

Thanks