FIESTA 2007 heater motor and switch problem
 

right got a 2007 fiesta tdci and had a problem with the heaters not working, first it was 1\2\3 the 4th worked for a while then that packed up. replaced the resistor pack still nothing, ive taken out the fan motor and benched tested it and it works........ i did a power probe test on the plug that goes into the fan. one wire is constant postive and the other was faint postive but if i wiggle the heater knob on the dash it flucuates between faint pos and slight neg the number 4 should be propper full neg but wwiggle it it goes on and offish...... could it still be a faulty resistor pack even tho its new or the switch knob that controls 1/2/3/4.......??? or could it still be the fan.......

Anyone...??