The neither the 5-blade cooling fan, nor the secondary electric fan are engaging when the engine temp rises. How do I trouble shoot this? The secondary electric fan engages when the A/C is operating. I have an '85 Euro model with three sensors in the theromostat housing. Going from right to left the first switch has three wires, and I assume is the temp switch for the solenoid fan coupling and the 2-stage aux fan. I assume this witch is bad. How do I check it? The second switch (two-wire) is for retarding the CIS ignition system as the temp rises. How do I check it? It is supposed to retard he ignition by as much as 5 degrees as the temp changes. I have no idea if it is functioning or not. (On my 190SL I make this adjustment manually when driving on a hot track or hot (summer)city streets.) I have no idea what the third (single pole) switch is for. All fuses look good.
190 E 2.3-16
Virginia Section MBCA