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I have a 2019 S-LSA Czech Sport Cruiser that uses a 912 ULS and is starting to show a 20 degree difference between the coolant temperatures.  It makes me think that one of the sensors might be going bad but I wanted to hop on hear and see what others might have in mind.  Thanks for any and all advice!

  • Re: Different coolant temperatures

    by » 5 weeks ago


    Unless you know which one is correct you will have to substitute a 3rd sensor prove which one is good. You could use the oil temp sensor since they are all the same. You need to determine whether it is a gauge, wiring or sensor fault.

    You could just connect a resistor from ground to each of the sensor wires and see if the gauges read the same. I can't remember what value you need, from memory something like 150 ohms gives about 100 degC.


  • Re: Different coolant temperatures

    by » 5 weeks ago


    Thank you Kevin.  The new sensor seems to have fixed the issue.


    Thank you said by: RotaxOwner Admin

  • Re: Different coolant temperatures

    by » 4 weeks ago


    An apparent difference in cylinder head temperatures can be caused if a sensor is not making good conduct with the tip of its thermowell (i.e. the socket).  I would suggest that you can first test the sensors by removing both sensors from their sockets and dipping them into a thermos flask of boiling hot water.  You could check the readings on your CHT gauge against a thermometer.  They should be within 1 °C.  Pack the thermowells generously with heat-conducting paste.  Insert the sensors into their thermowells and make sure that the tip of each sensor makes good contact with the tip of the well. A small gap can cause the sensor to read a lower temperature.  Tighten the nuts to hold them securely.  Test run the engine.  Sometimes it can take two or three attempts to get the sensor seated properly. 


  • Re: Different coolant temperatures

    by » 3 weeks ago


    I'd like to mention that the temp sensors (VDO) have a tolerance of aprox. +/- 7%-8% in the range we need them. That to me seems a pretty wide range. If you compare 2 sensors, one +8% the other one -8%, based on lets say 120C, one may give you a low ~110C and the other one ~130C. Have tested three sensor in an oil bath and found the tolerances confirmed. The test has changed my view on temp readings quite a bit and I'd rather have a more accurate set up.

    Regards

    Peter


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