dual climate heater control issue

[hank murawski]

I have a 2006 silverado 3500 LT  dually 6.6 duramax motor, my heater motor comes on when it wants to, mostly not

i checked the wiring at the resistor and at the motor everything seems to be ok. Good ground, has 12 volt power, 

the only wire that i do not know is the small purple wire, that i believe is the signal wire. Is there a relay between the controller and the resisterthat is bad. 

 at first i thought it was the resister, got one from rock auto, nothing worked, then i thought it was the contoller, that also did not work. sent everything back.

It is winter time here in New York and i am cold, hopefully someone can send me in the right direction so i can get some heat.

[davester]

Are the connectors good, particularly at the resistor pack?  The actual connectors are known to fail over time, as they seem to be made to just barely be good enough to work (as in, if any more current went through them, they would burst into flames).