You have to take the a/c control panel off. You may mess up more than $75 worth.
The heater resistor is quite simple to change. Unplug the wiring harness from the heater resistor. Remove the heater resistor retaining screws. Reverse the process to install your new heater resistor.
You can install a resistor in a 2009 Kia Sedona, first locate the heater box under your dash, remove the two screws, and replace with a new resistor.
the heater blower resistor is located on the passenger side footwell near the firewall. a complete how-to replace the resistor, along with photos is available on newcougar.org http://www.newcougar.org/forums/how-tos/3732-fixing-heater-blower-resistor-install-photos.html
where to find heater resistor 2004
Heater blower resistor is what controls the low medium high speeds...
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Location of 2007 heater blower Transistor resistor
In general the heater blower motor speed resistor is located in close proximity to the blower motor.
The heater resistor coil is located on the blower motor on the 2006 T300 Kenworth.
It uses a cable to change from heat to cold, it will start sticking and then eventually get stuck. Be careful not to break the switch, it costs around 400$ at the Mitsubishi dealership for them to do the repairs. You have to get in behind the dash and lubricate it, which can be very tricky.
Heater fan and cooling fan.