Heater Blower troubles

My 93 cherokee is not ready for winter.

My heater fan/blower only runs when the switch is on the HIGH possition. It is all or nothing.

I am wondering if this is a motor problem or a controler problem.

Which should I replace first. Any ideas would help

Classic problem with good write up on the fix
http://www.geocities.com/chmwatson/FAQs/Jeep/HVAC-fuselink_fix.html

great link. used it last year when mine puked. my resistor was fine....I just had some corosion that I cleaned up and it worked like new again.

its more than likely a blower resistor problem. the resistor is bypased when in the high position allowing full charging system voltage to the fan for high speed. the resistor reduces the voltage for each of the lower speeds, and when it is burned out you will only have high. a blower motor with high resistance can cause the resistor to fail also.