Chrysler Repair: The fan only works on the highest setting, blower motor resistor, 1999 plymouth voyager

Question
I have a 1999 Plymouth Voyager minivan with a V6 engine. Two summers ago the fan/blower only worked on the highest setting, including when it was on air conditioning and heat. I had someone look at it and he fixed it, but I don't know what he did. He indicated it had something to do with a nut or bolt that had either rusted or come loose, I'm not sure which to be honest. Then during the winter that same year, it happened again and I took it back and the guy fixed it again. It's been fine since, but then this summer it's doing it again and I can't get in touch with the guy. Is there something I can do or look for to fix this on my own?

Thank you.

Answer
Hi Justine,
I would not know of a fix that involves a nut or a bolt. The usual reason why it only operates on high speed is that the lower speed resistors in what is called the blower motor 'resistor block' have burned out. So you buy a new resistor block at an auto parts store or a dealer.
It is mounted in the firewall and accessed from the engine compartment, at least that is how it is shown in the '98 shop manual that I have. It is on the passenger side, with the resistors positioned in the fresh air intake plenum. There are rectancular opening in the plenum and you reach inside one of them to get to the block that is mounted adjacent to the opening.  It has a rectangular plug with 5 wires. You will see it very close to the right side strut tower (the large metal structure in the corner of the engine compartment (one on each side)), just below a 5 sided opening, under the wiper module. If you reach through the adjacent rectangular opening you can feel it. The plug is on the front side of it, so look for a multi-wire plug as another clue as to its location.
Once you remove the plug, notice there are some etched dotted lines on the driver's side of the flange. Insert the tip of a screwdriver about the width of those lines between the flange and the firewall and gently push in on a spring clip tang while simultaneously prying outward to release the block from the firewall.
When you put in the new one, make sure the resistors are not touching one another. If you get the part first you will know what to look for.
Roland