Wiper electrics

[cj847]

I am trying to figure out my wipers on my 66 c10.

I have tested the motor independent of wiring and it is good.
I tested the switch and it is good.
I tested the wiring between the two and it is good.

Not sure what is wrong, but the motor will occasionally run via the switch then quit.

Just to check my understanding of the wiring- The yellow wire brings power from the fusebox, the light blue wire provides ground via the switch. And the dark blue wire provides ground for the squirter.

What am I missing? I tried wiggling the switch to see if it was intermittent but it didn't affect anything.