First my heater only worked on high, so i changed the resistor. And it was working on all the speeds. Then I noticed that when i try to put it on defrost only or to change the settings it doesn't change, the heat just blows out of everywhere. About a month after we changed the resistor, I noticed the fan would work on all the settings except high. Now just a couple weeks ago it started to make a loud noise and it stopped working all together. You can hear it going but barely anything at all comes out of the vents. I let the truck run for about 45 mins and my windshield was barely defrosted.