Automotive Air Conditioning Information Forum

Okay. So usually on aftermarket underdash ac the red wire to fan goes to the ignition, green wire goes to binary or trinary switch , then to compressor.

This old Mark IV has no thermostat. I recently bought a service manual for Mark IV ac. I found the wiring diagram. (See pictures) When I look at the temp control it looks like a huge device into the evaporator core without power connected.

I have 2 of these & both have the fan wire connected. (See picture) The only wire loose is the brown wire that’s supposed to go into the clutch fan? How do I wire this thing up? I want to go with a sandon style.

This is the common method for wiring most all aftermarket evaporators.

I hooked the brown wire up as the fan. Still not sure what runs to to the compressor side.

I spoke with someone and my hypotheses was right. There is no bulb for temp sensor but it is actually built into the switch itself. I will take apart my parts mark IV soon to look it over.

separately you described low air flow from Mark IV Monitor:
1) Slow motor: if bearings are misaligned, tap several times on each motor shaft with motor running and perpendicular to shaft.
2) If bearings are dry, drill tiny hole in end cap near bearing and squirt in oil.
blower wheels must have forward curved blades.
3) I fixed a dove hunter's Monitor low air flow after he threw doves on his pickup's floor board by removing feathers from inside the blowers and on the back of the evap coil.
4) Check voltage at blower terminals.
hotrodac