I was lookin' for info on this issue. I have a '98 Ram and the blower motor won't run at all. For a while, it would run and then stop, now not at all. I've replaced the ballast resistor and test run the blower motor from an external battery (it ran fine). I bought a junkyard switch and installed but the problem isn't solved. I used a test light and got nothing on the connector to the switch. So, I know my problem is somewhere from the plug for the switch back to the fuse box. I saw the post by 'HeyYou' with the wiring diagram. Thanks a bunch for that 'cause if I read that correctly there is a relay (it says 'in the PDC, which I assume means power distribution center). I haven't been able to find that relay identified on any schematic of the PDC but I greatly appreciate the info. If I find it, I'll let ya know.
(BTW...Hi everyone, this is my first post here.)

 

Welcome to DF.

Keep in mind, The switch provides a ground, for an already powered circuit. You should have 12 volts at the blower on one of the terminals. The relay in the PDC is controlled by the ignition switch, with the key in run, the relay is grounded, thus sending power to the blower motor. Dodge had some really odd ideas about electrical circuits.......

 

Just wanted to follow up with everyone about my blower motor not running. I got it working by changing the blower motor relay located in the power distribution center (under the hood). As soon as I pulled the old relay, it was obvious that it was fried. I got a new relay at the Mopar dealer for $11.23 including tax. The info that I got here hepled tremndously. I would especially like to thank 'HeyYou' for that schematic. My shop manual didn't show that. Without that schematic, I wouldn't have even thought about a relay for the blower motor.
Thanks again to all!