I have a 02 5.4 4x4 with a strange (problem) - feature? When the heater fan -blower is on, lets say position 2 and i am driving at 80 KM/hr (50 mph) then speed up , the fan sounds and acts like i have turned it to the next higher position and continuea as speed is increased further, take foot off accelerator and fan speed immediately drops. No alterantor or voltage problems and not low voltage as may be experienced when ideling with all accessories on.It seems to me that it works like the radio volume should ( speed sensitive volume) , which does not seem to work . I am wondering if this unit may have been miswired at factory. Anyone heard of a similar situation?

 

The only thing i can think of is that at high speed the air flowing in to the vents takes the load of the blower (kind of like ram air) and the blower spins faster. I don't know if thats true or not but it's a good theory Will it do it even if the heater is set to recirculate, instead of fresh air?

-Jon

 

sounds like you have a vac leak. poss it is just changeing vents and makeing it sound louder. just a thought. feel the air see if it goes from dash to defrost on accel. good luck