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.

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Robby Ackerman

190 SL
190 E 2.3-16
300 D
Past President
Virginia Section MBCA

Unless the engine goes above 105C none of the OVERHEATING switches operate. Fan clutch doesn't lock up until 100C. How hot does the engine run?

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MERCEDES BENZ MASTER GUILD TECHNICIAN (6 TIMES)
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 16V ITS SCCA racecar

it will creap up to 120 C without engaging.

The car is equipped with a manual (override)switch the aux electric fan. I've been turning it on at about 115 C and off at 90 C.

Change the switch...its most likely the fan switch. Inexpensive. Give your vin# and you should get the right one but I believe there is only one 3 prong one. The secondary fan will kick in when the AC is on. Does the override switch engage the big fan? I have never seen this...is it an aftermkt add on? If so is it fused?

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yal
88 230E (W124)
euroheadlights,
clearcorners,
smoke/red tailights
98 e420 sport replicas

Yal

The aux fan switch was in the car when I purchased it. It can be used to turn on the Aux electric fan at will. I expect it is fused. This switch is rocker switch between the passenger window switch and the right side mirror control. I'll order the part you mentioned. Thanks.