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Thread: Electric fan confusion

  1. #1
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    Electric fan confusion

    Ok, so I have a 1.9, M44. It has this original electric puller fan instead of a viscous:

    http://www.realoem.com/bmw/showparts...62&hg=64&fg=55

    As per the aux fan that sits in front of the rad, it is controlled by the double temp switch in the side of the rad as well as by the aircon.

    When the aircon is turned on, the fan correctly runs at low speed. When I bridge the contacts in the plug for the double temp switch I can get it to run at low or high speed, depending on how it's bridged.

    However, when I let the engine run up to temperature the fan doesn't kick in at low speed and just comes in at the point where the high speed side of the switch comes in.
    I've replaced the double temperature switch as well as the wiring plug that attaches to it, as there was some corrosion that could have been an issue, but no difference.

    I've also swapped the low speed fan relay with another.

    An ideas why the low speed doesn't kick in?

  2. #2
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    The high-speed relay de-energizes the low-speed fan circuit when it gets energized. I suspect that your high-speed relay is constantly open (or there is bad wiring) in its low-speed circuit.

    The diagram in the Bentley manual is pretty clear on what wires and circuits you should trouble-shoot. Unfortunately, the high-speed relay is the purple one and there is not another one to easily swap it with.

  3. #3
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    But if the high speed relay was the cause, surely the low speed wouldn't come on when I jump the contacts in the plug to the double temperature switch?

    It's kind of like everything works as it should when manually triggered, but that the double temperature switch doesn't trigger the low speed circuit, despite it, and the plug connected to it being brand new (and the symptoms being identical to the old one).

  4. #4
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    Looking over the schematics in the Bentley manual, there is nothing else special about the circuit. The temperature sensor simply supplies ground to each of the two relays that in turn supply power to the two fan circuits.

    You've fault-isolated to the temp sensor, but replacing that did not solve the problem. The only thing left that I can think of is a "pushed pin" in the temp sensor connector. Somehow, the connector is not making contact to the low-temp pin when plugged in. The high-temp and ground contacts seem to be working. Inspect both halves of that connector or maybe pull the low-temp relay and see if Pin 4 (the ground side of the coil) gets driven to ground when there should be a call for low-speed fan.

    Looking over the Bentley schematic again, just noticed that the temp sensor plug wires are Brn for ground, Blk/Grn for low temp, and Blk/Grn for high temp, an unfortunate combination of colors. Do you think you could have reversed the two Blk/Grn wires? If they were reversed, a low-temp call would result in a high-speed fan and then a high-temp call would be ignored, since the fan would already be on high.

  5. #5
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    http://wedophones.com/Manuals/BMW/19...g%20Manual.pdf
    This will give you the whole wiring diagram.

  6. #6
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    Quote Originally Posted by Blacklane View Post
    Looking over the schematics in the Bentley manual, there is nothing else special about the circuit. The temperature sensor simply supplies ground to each of the two relays that in turn supply power to the two fan circuits.

    You've fault-isolated to the temp sensor, but replacing that did not solve the problem. The only thing left that I can think of is a "pushed pin" in the temp sensor connector. Somehow, the connector is not making contact to the low-temp pin when plugged in. The high-temp and ground contacts seem to be working. Inspect both halves of that connector or maybe pull the low-temp relay and see if Pin 4 (the ground side of the coil) gets driven to ground when there should be a call for low-speed fan.

    Looking over the Bentley schematic again, just noticed that the temp sensor plug wires are Brn for ground, Blk/Grn for low temp, and Blk/Grn for high temp, an unfortunate combination of colors. Do you think you could have reversed the two Blk/Grn wires? If they were reversed, a low-temp call would result in a high-speed fan and then a high-temp call would be ignored, since the fan would already be on high.
    It's definitely not a problem with the connector, as I replaced that as well as the sensor, and it tests ok.

    The wiring is actually black/green and black/grey, but easily confused in the manual!

    I think I may buy another connector for the double temp switch and make up a dummy with just three tails, so i can test that the outputs switch correctly.

    Z3HACKER1979 - thanks for the link, but I'm already working from the ETM.

  7. #7
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    I got cha, sorry didn't know. I hope you find out the problem. Your welcome

  8. #8
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    same problem as mine, as I explained here
    http://forums.bimmerforums.com/forum....php?t=1839083

    I think BladeRunner found better words than me to explin the problem, but is quite IDENTICAL. I changed temp switch, checked the connector and seems ok, I also changed the two relays, but lo-speed won't start unless AC switched on.

  9. #9
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    Quote Originally Posted by Blacklane View Post
    Looking over the schematics in the Bentley manual, there is nothing else special about the circuit. The temperature sensor simply supplies ground to each of the two relays that in turn supply power to the two fan circuits...
    This.
    Hello. I like you.

  10. #10
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    did you tried my "little test"? I rode you're skeptical, but is a to-do test to be SURE.

    http://forums.bimmerforums.com/forum...8&postcount=20

    you won't be sure your wiring is pre or post modification until you make that test. ETK dates are not so accurate (as was for my car) and testing the bulb itself (and his pin) without invert the wiring or testing in the fuse box.

    And don't be afraid, you can't burn/broke anithing. Probably NOW you're short-circuiting the vent wiring

  11. #11
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    Subscribed. I noticed this about my car as well. Please update when you've found something. If I have the time to look into it and find something I will do the same.

    * 19x10 & 8.5 Work VS-XX -Rogue 18mm spacers * Hankook Ventus RS3 * H&R coil-overs * Dinan strut brace * Magnaflow 14815 custom stepped tips. * TT stg2 Turbo -416rwhp * AEM truboost * Mocal / Ireland Engineering oil cooler * Roadstersound 8 with custom set-up * flipped hats *RF Rear Subframe Kit *STG3 F1 Racing Clucth & Flywheel

  12. #12
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    thermostat is ok? is the first thing to check (and check if is right as stated..and I solved! ). to be sure is not a fan problem, have you tried jumpering thermostat connector pins? what year is your car?

    in my thread I've made a (confuse :P ) explanation of the tests I made to verify various components, take a look
    Last edited by resunoiz; 06-14-2012 at 06:04 AM.

  13. #13
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    Mines a 98 m roadster. New thermostat, fan switch, when bridged works great, ect ect ect, same senario as the op.

    * 19x10 & 8.5 Work VS-XX -Rogue 18mm spacers * Hankook Ventus RS3 * H&R coil-overs * Dinan strut brace * Magnaflow 14815 custom stepped tips. * TT stg2 Turbo -416rwhp * AEM truboost * Mocal / Ireland Engineering oil cooler * Roadstersound 8 with custom set-up * flipped hats *RF Rear Subframe Kit *STG3 F1 Racing Clucth & Flywheel

  14. #14
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    Quote Originally Posted by billyr3d View Post
    Mines a 98 m roadster. New thermostat, fan switch, when bridged works great, ect ect ect, same senario as the op.
    98..ehehehe.

    first question: with AC on, the vent starts?

    if yes, try this test.
    leave thermostat connected, engine cold. Start the engine, and measure tension on lo-speed relay (yellow, with numer 2 on the image). Fuse box may vary, but the relay is in that position in any case.


    remove that relay with engine on measure tension on pin 68b (point a tester terminal on a mass point on engine chassis and another on this pin). wait for engine to warm.

    and control constantly: when the car is cold, till the hi speed vent starts. at 80 the first thermostat contact will open, closing at 85c.(even if the low speed vent won't start). tell me what voltages you see on all stages.
    And don't be afraid, even if removing this relay for measurements, the hi-speed vent will start in any case (is ruled by the violet relay). is not afflicted by this yellow one.
    (hope my bad english is easy to understand).

    in this (italian..) guide I made, you can see several images of the pin(s) you have to measure on.
    http://www.mediafire.com/view/?hqeg2xe9ku5hzfj
    Last edited by resunoiz; 06-14-2012 at 08:43 AM.
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  15. #15
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    Fixed it bladerunner! So get this, the wiring was incorrect from the day it was made back in 1998. At the thermoswitch there are 3 pins - ground, speed one and speed two. The ground should be in position 2 (the middle pin) mine was actually on pin 3. Looks like low speed has never worked on my car. The high speed would activate at high temps controlled by the block temp sensor and the ac being operated. When placed in the right pins everything works great now. Check your pin locations, if brown isn't the Centre pin then you've got it. Good luck

    * 19x10 & 8.5 Work VS-XX -Rogue 18mm spacers * Hankook Ventus RS3 * H&R coil-overs * Dinan strut brace * Magnaflow 14815 custom stepped tips. * TT stg2 Turbo -416rwhp * AEM truboost * Mocal / Ireland Engineering oil cooler * Roadstersound 8 with custom set-up * flipped hats *RF Rear Subframe Kit *STG3 F1 Racing Clucth & Flywheel

  16. #16
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    Quote Originally Posted by billyr3d View Post
    Fixed it bladerunner! So get this, the wiring was incorrect from the day it was made back in 1998. At the thermoswitch there are 3 pins - ground, speed one and speed two. The ground should be in position 2 (the middle pin) mine was actually on pin 3. Looks like low speed has never worked on my car. The high speed would activate at high temps controlled by the block temp sensor and the ac being operated. When placed in the right pins everything works great now. Check your pin locations, if brown isn't the Centre pin then you've got it. Good luck
    another difference than mine.


    PS: IMPORTANT. BE SURE pin n. 2 is ground, and NOT as I explained you. I'm afraid that changing pin 2 and 3 in your thermostat (and not 1 and 3 as i did and tested) will plug first speed BUT short-circuiting the second one.
    if you mistake those pin positions, HIGHER SPEED WILL NOT START!
    try disconnect lo-speed pin, and see if higher speed works with your jumpering position. (did you made test I told you on relays? make the same test on hi-speed now). If your is right..mine is different too, mystery of bmw
    Last edited by resunoiz; 06-15-2012 at 03:16 AM.
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  17. #17
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    Quote Originally Posted by resunoiz View Post
    PS: IMPORTANT. BE SURE pin n. 2 is ground, and NOT as I explained you. I'm afraid that changing pin 2 and 3 in your thermostat (and not 1 and 3 as i did and tested) will plug first speed BUT short-circuiting the second one.
    if you mistake those pin positions, HIGHER SPEED WILL NOT START!

    That's not really correct - when the double temperature switch reaches the 'high' trigger point, all three contacts are joined internally, so at that point it doesn't matter which wire goes where. I have dismantled one of the switches and the way it works is that there are two contacts that are moved by a single plastic shaft, connected to a pair of metal discs that move the shaft as the temperature increases. First one contact is earthed, then the second is also earthed, at which point all three are connected. As the high speed relay kicks in, it cuts power to the low speed relay rather than having the double temp switch do it, presumably to avoid the danger of a 'dead' area between low and high which could occur if the switch was switching off the low at the point it was switching on the high.

    So, high speed will always start regardless of how the switch is wired, as long as all three wires are connected.
    Last edited by BladeRunner919; 06-15-2012 at 03:12 AM.

  18. #18
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    Quote Originally Posted by BladeRunner919 View Post
    That's not really correct - when the double temperature switch reaches the 'high' trigger point, all three contacts are joined internally, so at that point it doesn't matter which wire goes where. I have dismantled one of the switches and the way it works is that there are two contacts that are moved by a single plastic shaft, connected to a pair of metal discs that move the shaft as the temperature increases. First one contact is earthed, then the second is also earthed, at which point all three are connected. As the high speed relay kicks in, it cuts power to the low speed relay rather than having the double temp switch do it, presumably to avoid the danger of a 'dead' area between low and high which could occur if the switch was switching off the low at the point it was switching on the high.

    So, high speed will always start regardless of how the switch is wired, as long as all three wires are connected.
    interesting!
    different from what you "see" on the schematics (2 contacts)


    so he jumpered right the 1st speed in any case (closing the 1st contact) and all works for the reason you explained. cool!
    the only one has to make those "movements" now is you, bladerunner
    billye3d, what pin you interchanged? ground in pin 2, and the others?
    Last edited by resunoiz; 06-15-2012 at 03:34 AM.
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  19. #19
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    That's the plan for this weekend! Weather's looking terrible here, so I can hide in the garage messing about with the car.

  20. #20
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    Quote Originally Posted by BladeRunner919 View Post
    That's the plan for this weekend! Weather's looking terrible here, so I can hide in the garage messing about with the car.
    I'm sure you will solve!
    do you have the schematics for our cars?
    here different configurations found....



    this one is the billyr3d one, maybe yours:


    can you make a photo of the dismantled switch?
    I made a reportage fot this issue (in italian) and I'd like to add your information about switch internal contacts
    Last edited by resunoiz; 06-15-2012 at 04:00 AM.
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  21. #21
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    Well, you were right. Same part number, different pin-outs.

    I took the slightly riskier approach of disconnecting the plug to the double temp switch and monitoring the three pins as the temperature increased. I was monitoring the coolant temperature in Carsoft, so I was fairly confident about not blowing the engine up!

    As you found, pins 2 & 3 connect at the lower temperature point, and all three connect at the higher point.

    Like you, I now have a fully functional fan.

    On top of that, I also fixed my ASC today using DIS, so I'm a pretty happy chap!

  22. #22
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    Quote Originally Posted by BladeRunner919 View Post
    Well, you were right. Same part number, different pin-outs.

    I took the slightly riskier approach of disconnecting the plug to the double temp switch and monitoring the three pins as the temperature increased. I was monitoring the coolant temperature in Carsoft, so I was fairly confident about not blowing the engine up!

    As you found, pins 2 & 3 connect at the lower temperature point, and all three connect at the higher point.

    Like you, I now have a fully functional fan.

    On top of that, I also fixed my ASC today using DIS, so I'm a pretty happy chap!


    so happy to be useful for you

    what's your final pin disposition so?
    2 (higher pin) ground, 3 lo spees, and 1 hi speed?
    is possible to you make a photo of the dismantled switch?
    miss ZUKU!

  23. #23
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    Quote Originally Posted by billyr3d View Post
    Fixed it bladerunner! So get this, the wiring was incorrect from the day it was made back in 1998. At the thermoswitch there are 3 pins - ground, speed one and speed two. The ground should be in position 2 (the middle pin) mine was actually on pin 3. Looks like low speed has never worked on my car. The high speed would activate at high temps controlled by the block temp sensor and the ac being operated. When placed in the right pins everything works great now. Check your pin locations, if brown isn't the Centre pin then you've got it. Good luck
    Let me see if I've go this right. The connector in question is attached to the sensor screwed in to the passenger side of the radiator on the S52?
    Last edited by spacecowboy; 07-08-2012 at 06:41 PM.

  24. #24
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    Quote Originally Posted by spacecowboy View Post
    Let me see if I've go this right. The connector in question is attached to the sensor screwed in to the passenger side of the radiator on the S52?
    yes, it is.

    sensor is n.5 in the schematics:
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  25. #25
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    Quote Originally Posted by spacecowboy View Post
    Let me see if I've go this right. The connector in question is attached to the sensor screwed in to the passenger side of the radiator on the S52?
    Quote Originally Posted by resunoiz View Post
    yes, it is.

    sensor is n.5 in the schematics:
    Just double checking, but this one? Please bear with me, I'm going somewhere with this one from information I read above. My sensor & connector is in the picture below. Look at the wiring closely.


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