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Thread: Cooling system problems (cooling fan)

  1. #1
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    Default Cooling system problems (cooling fan)

    Hello. New to the forums and need some help. I've been chasing an ongoing issue with the 90 since we got it 2 years ago. The cooling system in our 2.5T has been giving trouble to no end. Been chasing leaks. Replaced water pump, radiator, thermostat housing, and upper hose respectively. Every time I fixed a leak a new one would spring in that order. I've since realized the cooling fan does not operate at all no matter how hot the engine is and doesn't activate with A/C either. Checked for power at the cooling fan connector with test light and confirmed power to the fan. Tried to test pink signal wire but couldnt make it do anything. Gave battery power to old fan and it didn't move. Decided to replace cooling fan with a new TYC unit and still no luck. I'm out of ideas. Any help?

    It's a 2005 2.5T AWD with 200k miles on the clock.

  2. #2
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    Quote Originally Posted by piggymoo66 View Post
    I've since realized the cooling fan does not operate at all. Checked for power at the cooling fan connector with test light and confirmed power to the fan. Tried to test pink signal wire but couldnt make it do anything.
    If you are doing this work yourself, you need to purchase some diagnostic help. (it will pay for itself quickly) An illegal copy of 2014d VIDA with a chinese copy of a Dice unit is available for less than $90. Vida (on your win 7 Pro computer) will allow you to easily diagnose whats wrong.

    Is the control unit sending a signal to turn the fan on? (meaning the aftermarket fan unit you bought does not work) Plug into VIDA and find out. As a Former shop owner that specialized in Volvos since 1980 (till 2018) - I found whenever I bought the cheap aftermarket radiator fan, they did not work - so I only purchased and installed the factory part from a volvo dealer.

  3. #3
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    UPDATE: I was able to get a wiring diagram from a friend who works at a shop. Started probing the circuit (pink wire) with multimeter. Fan connector to underside of fuse panel has continuity, and there is continuity through the panel itself.

    Since the ECT is new and the A/C activates properly, the ECT and pressure switch circuit can be ruled out. The only thing left is the wire to the ECM or the ECM itself.

    Sidenote: When I flipped the panel over I noticed the fuse for the power circuit looked much newer than the others next to it. Seems like someone else in the past has attempted to fix the issue.

    I planned on getting VIDA eventually to diagnose the ABS/AWD faults (that's a whole other issue) but this problem seems simple enough to do without special software. Just needed to stop and think about electrical theory.
    Last edited by piggymoo66; 09-09-2018 at 07:51 PM.

  4. #4
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    Quote Originally Posted by piggymoo66 View Post
    this problem seems simple enough to do without special software. Just needed to stop and think about electrical theory.
    Yes, there is constant 12v power and ground on the two large wires, the small wire goes to the ECM and it tells the fan controller what speed to run the fan at. As far as i know there is no easy test for the signal on that small wire.

    It's possible the ECM is not sending the correct signal or the wiring is broken from the fan to the ECM. Unfortunately it usually requires a special tool to be able to remove the ecm to check continuity on the signal wire.

    I have replaced many fans (with the attached controller) and zero ECMs to solve a fan not working or staying on problem.

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