IIRC there is a 3-pin temp switch on the upper hose fitting for the aux fan and AC compressor cutoff. There is a single(?) post sensor beside it for EDS. There is a sender between the head and IP for the temp gauge. There might also be a temp sender for the glow relay just aft of the gauge sender. If the car has a BFS, there’ll be a 50*C temp switch at the water pump.

The ELR actuator that controls idle is on the back end of the IP. The control rod sensor connector is on top of the IP. The control rod sensor connector is about the only oil leak point that requires the IP to come apart to reseal.

Only the 603.96 (3.0) has the idle trim box.

I think you’re correct about the AC sensor with pigtails. No need for a fuse, just jump the wires on the car side of the harness. Most likely the AC circuit should be active for the fan to engage. This is the low speed fan switch. The high speed fan switch is part of the 3-post switch at the upper radiator hose fitting. If you have high speed but not low speed, check the ballast resistor behind the driver headlight. The coil can burn itself to an open circuit.

Sixto
98 E320s sedan and wagon
02 C320 wagon