I do not know where the resistor is behind the headlamp.
>

OK. So you now see you were jumping a DISCONNECTED sw before ..
So,now we know the integrity of the a/c low fan is OK ,
[ including the resistor]
EXCEPT, you do not see it come on with a/c on ..
Well. it won't til the high side gets up to pressure
That takes a HOT/HIGH ambient temp condition.[and you are is Seattle]
If you have a good , Hot day and it still does not come on, you may just be short [just a little ] of freon..this allows for a/c cooling, but not 100% ..IOW- not enough to trip the sw..[ or , bad sw] Gauges are require here for diagnosis...

I will post the other question in another post to save confusion