One problem related to defogger heater has been reported for the 1998 GMC Jimmy. The most recently reported issues are listed below.
Took car in for repairs on 01/30/01 windows fogging up. Got call from dealer 02/01/01 car ready for pickup they couldn't find anything wrong. Receipt said: pressure test coolant system-no leaks detected defroster system operating to factory specs. Picked car up 02/01/01 windows fogging up and bad odor in car. Returned car 02/02/01 windows fogging up bad odor. Got call 02/05/01 car needs heater coil and coolant flush. My car is not very old but this is the second major part to go bad. (transmission was first).