1998 Chevy Venture Turn signals/wipers

I doubt the two are related.

The resistor is probably the problem on the blower.
The blower getting full power will be on high speed.
When resistance is put on the motor it will slow it down depending on the particulat resistance. The 3 lower speeds are varied amount of resistance.

On the turn signals, I Would suspect the turn signal flasher. Do they clcik or anything?

It's on the underside left side of the dash near the steering column. Buy one beofre hand so you can see it easier and know what to look for.

Please accept my apologies for mis-reading.
Yes they are very likley related.

The GM vehicles of that period are notorious for the solder joints in the circuit boards to crack and cause the wiper motor to not work or work intermittently. Turn on the ign. Switch and the wiper switch and wiggle the connector at the wiper motor. If the wipers suddenly start working you have broken solder joints in the circuit board.

I knew a tech that did not usually do not replace the board, He used a lighted magnifying glass and a solder gun and resolder the broken joints.

You can verify this also my checking for power at motor/circuit board.

Napa carries the motor and circuit board as an assy. Other store may as well.