I just purchased a 2003 Trail Blazer LS 5.3L V8. I have got a problem with the fan motor for the heat and air. I can start the machine up have the heat on, and press the button to turn the fan speed up and down and it works great. You can let it run all day with no problem, shut the engine off start it back and the fan motor want work. This happens quite often, when this does happen sometimes you can turn the heat off then back on and the fan motor works fine, and sometimes it want. Seems like it only happens when you power on or off the fan motor, I do not believe that it is the motor, it looks as if it has been replaced by a new one. I have also replaced the relays under the hood without any difference. Sometimes I can go for days and it will work fine, it will never shut off unless powered off, sometimes it will come on and times it will not. The longer it goes the worse it is getting, so it seems. Is there any suggestions?