Mercedes-Benz W126 cooling system and fan
Why does the W126 overheat in traffic?
A common cause is the fan's viscous clutch, which no longer drives the fan properly. Overheating can also show up as coolant being pushed out. Do not remove the thermostat, because then the water circulates past the radiator.
When does the W126 electric fan start?
A car with air conditioning has an electric auxiliary fan in front of the condenser. It starts when the engine temperature exceeds about 105 degrees or when the air-conditioning pressure rises too high. If the fan does not turn, also check the fuse and the control relay.
What is the fan's series resistor?
The series resistor is under the brake booster. The fan receives voltage through it at lower power, and when the coolant is over 110 degrees the resistor is bypassed so the fan runs at full speed. All 280 models have only one speed and no series resistor.