#Coolant level indicator verification#
#Coolant level indicator series#

Please note that the sensors supply fixed value resistance (180 and 120 ohms if i remember correctly) when open, and a short circuit when closed - so they do not behave as a pure 'switch'.Įxperienced benz repair shop will perform the above procedures and find the faulty component quickly. Things to check is the coolant level sensor (inserted in the lower part of the expansion reservoir), the washer level sensor (in the left front wheel housing, towards the bumper, easily accessible after removing front left wheel and folding the black plastic liner) and the wiring if the sensors check out okay. Malfunction in one of these components can lead to displaying the low coolant warning, even though the coolant is OK and the sensor may be also okay.

#Coolant level indicator series#

The W203 (as many other Mercedes series) has funny circuit for monitoring the coolant level - it is connected in series (!) with washer fluid level sensor. The float in my tank is bad and it drops right to the bottom even though the coolant level is fine. When I read about how the coolant level sensor works (magnetically in conjunction with the float) I realized that I had to order a new expansion tank. I still don't know for certain, but apparently MB uses a float type sensor in some vehicles. I ASS-U-ME'd it was just a probe, but it very well may not be. Correct?Īlso, I looked at the wiring diagram and it shows nothing about the washer level sensor in the coolant level sensor circuit.Ī very good question. Since high resistance is an open circuit, it should read open when the level is full. Refer to the appropriate diagnostic information. The coolant low indicator, a diagnostic scan tool is Of the instrument cluster circuitry that controls Instrument cluster can be diagnosed using conventionalĭiagnostic tools and methods. The engine coolant level switchĪnd the low coolant fluid level sense circuit to the The engine coolant level switch integral to the coolantīottle provides a hard wired input to the instrumentĬluster circuitry through the low coolant fluid That the low coolant fluid level sense circuit is not

#Coolant level indicator verification#

The engineĬoolant level switch also features a diagnostic resistorĬonnected in parallel between the switch inputĪnd output to provide the cluster with verification The Off position, whichever occurs first. Level full), or until the ignition switch is turned to Level switch resistance high = engine coolant Level sense input to the cluster changes (engine coolant

Remains illuminated until the low coolant fluid While the ignition switch is in the On position, theĬoolant low indicator will be illuminated. Level switch resistance low = engine coolant level low) Low coolant fluid level sense circuit (engine coolant Time the cluster detects an appropriate input on the I just found in the repair manual, the following information: