Ok, I think this is the correct section to post this in, so heres my problem. I have a 98 C1500 with a 4.3L in it. its a single cab. I just replaced the thermostat and the temperature sending unit i think, but both parts were on the upper rad hose thingy on the engine. I also put LEDS in my HVAC controls. The reason I'm telling you all this is because after I did both of these things my heater stopped working. I dont know if both of these things directly relate to that problem, But I thought it would be helpful to mention. Now, I live in Florida so I usually dony have to use my heater that often, but now as it is cold as ice outside, I start trying to use it in the mornings. Itll blow warm for a few minutes, and then blow ice cold again. My A/C works fine, but my heater does not work at all, Any ideas? Help please. Im freezing on my way to school in the mornings.