On the intake side of the cylinder head, which temp sensors are which and what is their function? I know that he 3 contact one between cyl. 3 & 4 controls the high speed on the aux. fan (confirmed bad), but what about the others? Which controls the cold start? TIA for any guidance. I have the CD's, brit Haynes and Bentley manuals and none offer clear explanations or locations.

Rearmost with the fancy 4-pin connector is for the ECU, single pin is for the tmp gauge, 2-pin is for the aux fan/s.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Don't know what car you are referring to...

Rearmost is a 2 pin, then a 1 pin. Aux fan is a 3 pin then a 2 hose in front.

Not drastically different. Rearmost 2-pin is for the ECU, 1-pin is for the temp gauge, 3-pin is for the aux fan (older style 105C/115C swtich), 2 post is a vacuum switchover valve one end of which goes to the EZL/ignition unit.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Thanks for the reply sixto!

Other than the 3 pin for the aux fan (which I know is bad) what about the functions of the others?

The car (my daughter's) has a cold start problem (stubborn) and that is one of the *next* troubles to diagnose. If the rear 2 pin is involved I will check this, along with the OVP relay.

I think you should back away from the car long enough to read through the archives in this forum. M103 cold start problems are covered thoroughly... too thoroughly. It could be a bad cold start valve, bad fuel accumulator, leaky injector, leaky fuel distributor or a number of other things. I don't recall reading that a bad temp sensor was ever an ultimate cause of hard starting. So that's my advice - start by checking fuel pressure at various points. The electronics don't do much until the engine has started. Note that I'm not an expert, just someone who spends too much time on this forum.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD