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  1. #1
    I'm New to PA
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    Radiator Fans Not Coming on

    Hi Guys,

    I finally bought and found my 1991 honda prelude (3rd gen), I have owned this car for 2 days and love it!!

    Problem is that the thermo fan switch doesnt come on, therfore the car will overheat while stationary.

    My guess is the fan switch...problem is that i cannot allocate where it is? Can anyone help and guide me to where the exact location is?

    Any response will be much appreciated.

    regards
    91Lude

  2. #2
    Junior Member
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    The fan switch is on the thermostat housing but if it wasn't working properly you'd have a check engine light coming on.
    Check maybe where they plug in at the bottom of the radiator and even try hot wiring them with a couple of wires from the battery to make sure they are working and not dead.
    The one closest to the battery should come on to cool the engine and the second one comes on when the air conditioning is turned on.

  3. #3
    Premium Member PJF_Lude's Avatar
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    Quote Originally Posted by itsmee View Post
    The fan switch is on the thermostat housing but if it wasn't working properly you'd have a check engine light coming on.
    Check maybe where they plug in at the bottom of the radiator and even try hot wiring them with a couple of wires from the battery to make sure they are working and not dead.
    The one closest to the battery should come on to cool the engine and the second one comes on when the air conditioning is turned on.
    no, the switch for the fans is on the bottom tank of the radiator, next to the outlet, the 2 on the thermostat housing are for the gauge and the ecu. our fans are not controlled by the ecu.
    ~Ian~

    Anything thing I say is my opinion, all care, but no responsibility taken.

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  4. #4
    Premium Member SnowWhiteLude's Avatar
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    Just quickly on this, can anyone clarify is there a switch for this on the JDM B20A? My mechanic said that it doesnt have one, as my fans have never turned on since I have bought this, however I cant understand as to why they would remove that from the JDM and not other models - dont engines get hot in Japan?


  5. #5
    Junior Member
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    Thanks PJF, I stand corrected ......I thought the fans were controlled by both

  6. #6
    PA Janitor Bob's Avatar
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    Quote Originally Posted by SnowWhiteLude View Post
    Just quickly on this, can anyone clarify is there a switch for this on the JDM B20A? My mechanic said that it doesnt have one, as my fans have never turned on since I have bought this, however I cant understand as to why they would remove that from the JDM and not other models - dont engines get hot in Japan?
    Think logically Snowy.
    Why install fans if they don't turn on?
    You will have a temp switch. Even on a JDM.

  7. #7
    I'm New to PA
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    Thanks for all the help guys,

    Yeah both fans didnt come on at all.

    I will be attempting this tonight by looking for it at the bottom tank of the radiator. No engine light came on (phew). What I did last night was that I started the car while stationary (From cold) until the temperature guage went from normal then after 15 minutes went to nearly red. Immediately switched it off.

    Kind regards
    91lude

  8. #8
    Premium Member SnowWhiteLude's Avatar
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    Quote Originally Posted by Bob View Post
    Think logically Snowy.
    Why install fans if they don't turn on?
    You will have a temp switch. Even on a JDM.
    Thought they might work, simply not to kick in and run after the car is turned off. BUt yes, it is a little illogical.

    Cheers Bob! Time to find someone else perhaps to have a look at this....


  9. #9
    PA Janitor Bob's Avatar
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    Ah. Does your car have that engine bay temp sensor. That's the one that makes the fans work when the car is turned off.
    Some pics for reference
    Early 3rd gens '88
    http://www.preludeaustralia.com/manu...f100/16-76.pdf
    Later 3rd gens '89-91
    http://www.preludeaustralia.com/manuals/3rdGen/

    The coolant temp switch is at the bottom of the radiator. This is what operates the fans when the car is on. Cuts in at 90deg.
    The TA sensor on the firewall is the one that switches the fans on when the car is turned off and still hot.

  10. #10
    I'm New to PA
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    Thanks for the PDF stuff Bob been searching everywhere online for a 87-91 free manual,

    no, i only have the coolong fan relay + cooling fan (20amp fuse). Furthermore, I realised my 20 amp cooling fan fuse was blown- i put another one in and that went too..*scratch Scratch*

    At least i know my fans worked when i place the new 20 amp in only with the A/C on.

    One or the other, i will be busy this weekend trying to fix this problem as i have the thermo fan switch that is allocated at the bottom of the Radiator.

    Kind regards
    91lude

  11. #11
    PA Janitor Bob's Avatar
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    The full online manual can be found here
    http://www.preludeaustralia.com/manuals/3rdGen/

    There is also a thread with links to download your own copy too.
    http://www.preludeaustralia.com/foru...Manuals-Online

  12. #12
    Premium Member SnowWhiteLude's Avatar
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    Quote Originally Posted by Bob View Post
    Ah. Does your car have that engine bay temp sensor. That's the one that makes the fans work when the car is turned off.
    Some pics for reference
    Early 3rd gens '88
    http://www.preludeaustralia.com/manu...f100/16-76.pdf
    Later 3rd gens '89-91
    http://www.preludeaustralia.com/manuals/3rdGen/

    The coolant temp switch is at the bottom of the radiator. This is what operates the fans when the car is on. Cuts in at 90deg.
    The TA sensor on the firewall is the one that switches the fans on when the car is turned off and still hot.
    Will check and let ya know but yeah - mechanic is saying that it doesnt posses one. I cant understand why they would omit in on their own model though.


  13. #13
    Gold Member phattzy's Avatar
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    id say you have a short somewhere if it keeps blowning fuse's , or your fans might be no good ? id replace both factory fans with some davis craig unit ! slimmer , newer , and much better . good luck with it .


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  14. #14
    I'm New to PA
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    Hi Guys,

    Just a thank you to you all and an update, but i have seem to solved the problem. All I done was flushed the coolant out and topped it with good coolant (Nulon long life- Green) and changed the thermostat (Probably was stuck)

    No heating wotsoever so far (for now)..fan does come on, but only the left one when thermostat opens- when does actually two come on?

  15. #15
    PA Janitor Bob's Avatar
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    The other fan is for the A/C I believe. Been wrong before though.

    Actually. Come to think of it. Pretty sure both mine come on regardless of the A/C.
    My A/C is removed.

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