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Thread: No radiator hose temp sensor on a Z3 M54 vs E46?

  1. #1
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    No radiator hose temp sensor on a Z3 M54 vs E46?

    Hi all,

    I am a bit puzzled that the engine wiring loom for a M54 in a Z3 does not have a temperature sensor on the lower radiator hose - The M54 from an E46 does have itů

    Is it a question on wether the engine is fitted with a PWM controlled fan, which the ECU controls (that needs the sensor) or a more inexpensive viscous fan directly on the water pump pulley? (which could do without)

    Anyone that can come up with an explanation ?

    BR

    Janus


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  2. #2
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    Yes, no PWM fan so no lower radiator hose sensor. The M54 was retrofit into the Z3's and the Z3 maintained the E36 era fan control system with the aux fan switched on from the sensor in the radiator.

    I did think that sensor was on the body harness and not engine harness though but not completely positive.

  3. #3
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    To fit a PWM fan would require a redesign of the HVAC system as well, to request fan control from the DME. In the current system the HVAC knows nothing of the fan; it being controlled by autonomous temp and pressure switches.


    /.randy

  4. #4
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    The fan is entirely DME controlled, so I believe if you can supply the DME the required inputs - radiator hose temp and ambient temp - that you can just flash the DME with a PWM fan enabled tune and wire in the fan and it would work. The difficult part is really the ambient temp signal, as that signal is sent over one of the bus networks.

    I think it is possible the module that controls the S54 Z3M center console gauges (which includes an ambient temp gauge) would work, as that module passes signals over the bus - but not positive. I bought the S54 Z3M gauge module to test it, but haven't had time to mess with it yet.

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  5. #5
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    Yes, on the E46 the DME has total control over the fan. So how do you propose to notify it of A/C fan requirements from our primitive HVAC? Normally those requests are sent over CAN.


    /.randy

  6. #6
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    On the M52TU, M54 and S54 Z3's the A/C signal is sent to the instrument cluster which has an integrated IKE module. The IKE sends it over CAN to the DME.

    This is why to make A/C work on S54 swapped E36's you need to use a M54 or S54 canbus instrument cluster.

  7. #7
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    Thanks, that explains it ! I am swapping an e46 m54 into a M43 Z3, so the ECU probably expects the temp signal. I do have an Z3 M52 cluster.


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  8. #8
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    The DME should be reflashed to Z3 spec so it doesn't look for that signal.

    An M52 cluster would not work. An M52TU cluster will, but may need a wire added depending on what year the cluster is.

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