I have an 03 Caravan. Where do you find the resistor that controls fan speed?

In the duct work behind the glove box.

Hi ,
Just another quick answer.
Although it may be behind the glove box, mine was under the hood, ALSO in the air duct, but H*ll to get to, as it was directly below the channel for the Windshield wipers.
When I first got it out, having to pry it out with a screw driver, I thought I had a bad problem, as one of the terminals was completely corroded off. I was able to replace the terminal, reassemble the module to the harness & HAMMER it back into place. NOT FUN!!! but it works.
Good luck!
Horacemac