As many have reported, I too had no heat coming from the heater so I decided to go to extremes to fix the problem. One of my friends is a Mopar mechanic (Jeep in particular) told me that if not properly maintained, Jeep engines will develop a corrosion problem which will clog the heater core. Since my '99 Sahara has 136,000 miles on it and I have already flushed the system this past Spring with no success he advised me to do an extensive repair. So I bought a new heater core, A/C evaporator, new heater and radiator hoses and a new water pump. We found the heater core completely plugged; even trying to back flush it with high pressure water would not unplug it. The evaporator was leaking oil and the water pump empeller was very rusty and pitted. The engine block was flushed 5 times with "Iron Out" until the water passages looked new. The radiator was flushed until it ran clear. With all new parts and a proper 50/50 premix of antifreeze the system is now ready to give years of trouble free service as long as I properly maintain it. I could have done a cheaper repair but that just isn't my style and my friend said that was the worst case of heater core plugging he had ever seen. I have owned Jeeps all my life and never encountered a heating issue before but I had always bought new Jeeps and maintained them properly. This Sahara was purchased used and obviously was not properly maintained. A full weekend of hard work but worth every minute and every dollar spent. I now have a heater that will keep the cabin warm in the worst conditions winter can throw my way!