505 1.8 fan won't stop
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  1. #1
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    Default 505 1.8 fan won't stop

    Hi
    I got an electric cooling fan which operates on the original sender in the radiator.
    yesterday it started to work almost constantly after the first time it cuts in and out, even in fast driving, and it won't stop.
    is it a defective sender?
    Before it started i let the engine run couple of seconds without the belt so the water pump wasn't working. Can it be related?
    Thx

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    Fellow Frogger! Jinandfonic's Avatar
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    Risky running an engine without the water pump running? The sender is cheap to replace
    Citroen C5 II manual '05; C4 Exculsive '07; Citroen CX2200 Pallas '76; CX2400 C-matic Pallas '78

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    what sender goes there? there are so many with different ratings.
    i tried today 82-68, i didn't drive just let it idle. the fan cuts in too early, and still won't stop, just that now it runs too cool (the needle in the gauge goes back almost to the dot before the middle).
    on the old sender nothing is written.

  4. #4
    1000+ Posts Beano's Avatar
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    Too cool ?? You have a thermostat ?
    Last edited by Beano; 10th July 2014 at 07:59 PM.

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    Of course!

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    1000+ Posts Beano's Avatar
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    Ok...
    I don't know why it won't stop, but I wouldn't be too worried about it being on the dot underneath the middle.

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    Hi

    There are really not many reasons why the fan would not stop, first I would check to see if you have power to the fan when you shouldn't, if you have, then trace the circuit back to see where the power is being supplied from, e.g. switch or relay stuck on, if no power to fan, then you have a mechanical problem

    Regards
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    1000+ Posts Peter C's Avatar
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    Quote Originally Posted by TassieExec View Post
    Hi

    There are really not many reasons why the fan would not stop, first I would check to see if you have power to the fan when you shouldn't, if you have, then trace the circuit back to see where the power is being supplied from, e.g. switch or relay stuck on, if no power to fan, then you have a mechanical problem

    Regards
    Neil
    Yes, I would follow the wire back from the fan. When the engine warms up and fan engages I'd disconnect the wire from the thermostat at the bottom front of the radiator. If the fan is still engaged, it's a mechanical problem. I'm assuming the wiring setup is standard.

  9. #9
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    it's an electric fan which gets triggered by the standard thermoswitch in the radiator (don't know what rating it is), but it has also a 40A relay.
    until now it used to work in hot days when idling in cycles of 3-3.5 minutes, and the guage was steady at the middle, is that normal? (there's an a/c condenser in front of the radiator).

    i will buy another thermoswitch of 88-79 or 85-75 and see what happens.

    can it be that me letting the engine run for 5-10 seconds (from cold!) without the fan belt caused it too burn the head gasket?

  10. #10
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    Quote Originally Posted by 2pac View Post
    it's an electric fan which gets triggered by the standard thermoswitch in the radiator (don't know what rating it is), but it has also a 40A relay.
    until now it used to work in hot days when idling in cycles of 3-3.5 minutes, and the guage was steady at the middle, is that normal? (there's an a/c condenser in front of the radiator).

    i will buy another thermoswitch of 88-79 or 85-75 and see what happens.

    can it be that me letting the engine run for 5-10 seconds (from cold!) without the fan belt caused it too burn the head gasket?
    1) The relay has turned into a short circuit or the load circuit wires are touching.

    2) The thermo switch has gone short circuit or the wires are touching.

    3) The vehicle is running hot for a reason unrelated to the electric fan (unless it's running backwards) and the vehicle never reaches the cut-out temperature of the thermal switch. This doesn't fit the posted symptoms.

    4) Wiring fault causing failure of thermal switch. I'd double check your wiring and make sure the thermal switch is only switching the relay coil. It's only designed to pass 1/2 an amp or so.
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    well, i bought a 85-75 thermoswitch and still no good. once the fan cuts in it won't stop even on the highway.
    can the temp in the radiator go down to 75 at all?
    shall i try a 88-79 thermoswitch? or 92-82?

  12. #12
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    Quote Originally Posted by 2pac View Post
    well, i bought a 85-75 thermoswitch and still no good. once the fan cuts in it won't stop even on the highway.
    can the temp in the radiator go down to 75 at all?
    shall i try a 88-79 thermoswitch? or 92-82?
    2pac,

    Check your wiring especially the relay coil. Either the relay is "latching" ie once powered it remains held.

    Or could the fan motor be incorrectly wired into the relay coil circuit?

    If so, the ram air from driving forward will make the fan become a "generator" and thus the relay won't drop out until the fan stops turning.

    I assume the temperature reduces to "normal" when the fan is running as shown on the temperature gauge?
    If it stays "hot" on the temperature gauge you may have a non related over heating problem with the engine.

    Is the aircon compressor cluth connected into the circuit - this can cause issues too.
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    as far as wiring concerns everything is ok, i didn't touch the wires and it used to operate correctly.
    it all started after i let the engine run without the belt for couple of seconds (from cold).
    i thought the old thermoswitch has gone so i replaced it.
    however no overheating, the gauge is on the middle dot and even goes down from it toward the cool zone.
    the fan starts when the needle of the gauge is on the middle dot.
    the a/c is not connected at the moment.

    mmm, does it matter how the 2 wires are connected to the thermoswitch?

  14. #14
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by 2pac View Post
    as far as wiring concerns everything is ok, i didn't touch the wires and it used to operate correctly.
    it all started after i let the engine run without the belt for couple of seconds (from cold).
    i thought the old thermoswitch has gone so i replaced it.
    however no overheating, the gauge is on the middle dot and even goes down from it toward the cool zone.
    the fan starts when the needle of the gauge is on the middle dot.
    the a/c is not connected at the moment.

    mmm, does it matter how the 2 wires are connected to the thermoswitch?
    No , the thermo switch is just an isolated switch. At least the OZ versions are.

    Are the relay points "sticking" or are there loose strands of wire and possible short? Try another relay.
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    Quote Originally Posted by 2pac View Post
    the a/c is not connected at the moment.
    The electrical switching of the AC compressor clutch and the thermo fans is quite independent to the AC being physically connected....In other words it wont matter if the AC is connected or not, when you switch it on at the dash, the thermo fans should come on and stay on.

    Jo

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    There is an auxiliary a/c fan, which is not related to the radiator fan or to the thermoswitch.

    The thermoswitch triggers 2 seperate fans- one of the radiator and one of the transmission cooler, with 2 seperate relays, and they both won't stop now, so the relay is not the problem.
    I suspect the thermoswitch being 85/75 is too low. Should it be 88/79 or higher?

    Or the head gasket got blown

  17. #17
    1000+ Posts robmac's Avatar
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    Probably not a head gasket because the temp gauge says it's OK.

    I've attached the fan switch data as jpg because it was most expedient.

    505 1.8 fan won't stop-wp.jpg
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  18. #18
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    Thx robmac
    What I understand from this table is that normal operating temp at the water pump (and on the gauge) is less than 80?
    And that there is a very small difference in temp between upper and lower hose?

  19. #19
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    Quote Originally Posted by 2pac View Post
    Thx robmac
    What I understand from this table is that normal operating temp at the water pump (and on the gauge) is less than 80?
    And that there is a very small difference in temp between upper and lower hose?
    Average the figures to get a "ideal" temperature:
    Fan on at 82.25
    Fan off at 68.25

    There is 14 degrees "dead zone" (hysteresis) to stop fan turning on/off too rapidly.

    The engine will run in the temp range 68 to 82 , depending on ambient temperature, airflow though radiator and engine load.

    Something in my memory says 176F or 80c is centre of "normal". But there is alway a small range which is considered normal.
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  20. #20
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    I managed to read the small print on the old thermoswitch and it's 88/79 as per Haynes. Is it ok then to use 92/82?

  21. #21
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by 2pac View Post
    I managed to read the small print on the old thermoswitch and it's 88/79 as per Haynes. Is it ok then to use 92/82?
    That means the car will run hotter than intended. The turn on temperature is 4 degrees,and turn off temp is 3 degrees higher than the recommended. This sender could be designed for higher pressure radiator cap, ie where the coolant run hotter ?


    The hotter the engine gets the longer the fan will need to run/ greater the cooling air flow is needed to reduce the temperature to the turn off point.

    The ideal temp switch is the 88/79 which is designed for a 4lb cap. You are using a 4 psi/ 27kpa/.27 bar cap on the radiator?
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    The ideal temp switch is the 88/79 which is designed for a 4lb cap. You are using a 4 psi/ 27kpa/.27 bar cap on the radiator?
    i have no idea, nothing is written on it.
    however it's a heavy duty radiator, without an expansion tank.
    Last edited by 2pac; 3rd August 2014 at 04:26 PM.

  23. #23
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    Quote Originally Posted by 2pac View Post
    i have no idea, nothing is written on it.
    however it's a heavy duty radiator, without an expansion tank.
    With 504s and higher pressure caps the radiator and engine seems to survive up to around 7 psi, but the heater cores can fail. Although, you may not have a heater connected at all...
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  24. #24
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    Quote Originally Posted by robmac View Post
    Although, you may not have a heater connected at all...
    why are you so negative?

    when i bought the car it didn't work indeed, because the hoses were full of gunk.
    now it's 100%.

    as for the radiator cap, should i ever need a new one is it going to be 4 bar then?

  25. #25
    1000+ Posts robmac's Avatar
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    Not negative at all, with weather that seldom gets under 15 degrees and most often over 28 degress a heater is probably not required.

    I hope your new radiator cap will be 4lb (psi) ie .27 bar approx.

    4 bar = 58 psi which, even with a clean heater core is a bit high.
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