2nd Gen Non-Engine/Transmission HVAC fan only operates after cab temp. increases

[T.Banttari]

I have power at the fan fuse at all times (key on); Fan only operates after cab temp reaches a ceratin temp- or that what it seems like. Replaced both blower and resistor network- Once I bring truck inside and it warms a bit, fan works normal at all speeds (old fan did as well). Power to the speed switch is not there when cold, but it is when it gets warmer (?) in the cab. Looking for a schematic to see where the 12VDC "comes from" to the fan switch. Any thoughts?

(1997 2500 stock-350K+ Miles)

 

[Sticks]

Fuse #2 in the fuse block, to the Blower Motor Relay [gets power/closed in key on] (probably your problem), to the blower motor, to the resistor block, then ground (bad ground on the other side maybe).



Another end is Fuse 18 through the Headlamp Switch, to Fuse 13, to the AC Heater Control, then to the same ground (bottom right of the Instrument Panel).



Follow the rabbit trail to see where your power leaves.

 

[av8r]

I had similar problems a little while ago. Link