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Thread: New Fan Fail relay

  1. #11
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by DMC5180 View Post
    I get it now, your FAN RELAY delays power to the FAN FAIL 1 second from when the A/C clutch engages. Your New FAN FAIL splits the delayed the power input between the fans with a 2 second stagger for both to be ON. Now you have a total of 3 seconds of transition time to full power load on the charging circuit.
    That's correct.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  2. #12
    Senior Member Bitsyncmaster's Avatar
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    Here are some photos of the new fan fail boards. I'm putting this first one into potting tonight so I can do the same testing for temperature and the same testing I did for fuse blow time with a shorted fan.

    Note one MOSFET sits higher than the other because I ran out of board space and had to put an IC under that MOSFET.
    Attached Images
    Dave M vin 03572
    http://dm-eng.weebly.com/

  3. #13
    Senior Member DMC5180's Avatar
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    What's the blob in the last photo?


    Dennis
    DENNIS

    VIN 5180, Frame 3652, STAGE I, DM-eng Solid State Solutions (RPM Rly, Dm.Lt.Mod., Fan Fail Mod. , FAN Rly, HS.Rly) , HID sealed beam style headlights, SPAX user since 2009, Eibach springs, Mid-State Club Adj. Rear LCA's, DPNW poly-sway bar kit, DMCEU LCA Stabilizer link kit, DMCMW Illuminated door sills, Aussie Illuminated SS Shifter plate, GENUINE MOMO EVO Steering wheel, DELOREANA Extended View Side Mirrors w/ Heaters, DELOREANA LED Door Lights.

  4. #14
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by DMC5180 View Post
    What's the blob in the last photo?


    Dennis
    There is a 1/4 amp PTC fuse that drives the fan fail lamp output under that blob of RTV. Since I pot the units, I coat it with RTV so it can expand and contract if it heats driving an incandescent bulb or someone short circuits the lamp wire.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  5. #15
    Senior Member Bitsyncmaster's Avatar
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    Did a temperature test of the REV C and REV B at 30 amps (15 amps each fan) and results were almost the same.

    The hot unit voltage drop on the REV C is 0.0987 volts on one fan and 0.0931 volts on the other. The REV B hot unit drop is 0.1383 volts on one fan and 0.1395 volts on the other. So the REV C is producing less heat via the loads. Now the REV C draws 6 ma. more on it's internal 5 volt power but that would not produce that much heat.

    Here is my thought. Since the REV B fuses are not potted into the unit, all that heat does not get into my measurement of temp of the unit.

    Still more testing to do.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  6. #16
    Senior Member davidc89's Avatar
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    I have no clue what you are talking about, but I am definitely interested on this topic. Keep up the good work!
    Everyone is tough through a keyboard

  7. #17
    Senior Member DMC5180's Avatar
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    New Fan Fail relay

    Quote Originally Posted by davidc89 View Post
    I have no clue what you are talking about, but I am definitely interested on this topic. Keep up the good work!
    Dave is working on a New cold fusion circuit for his fan fail relay.😜
    DENNIS

    VIN 5180, Frame 3652, STAGE I, DM-eng Solid State Solutions (RPM Rly, Dm.Lt.Mod., Fan Fail Mod. , FAN Rly, HS.Rly) , HID sealed beam style headlights, SPAX user since 2009, Eibach springs, Mid-State Club Adj. Rear LCA's, DPNW poly-sway bar kit, DMCEU LCA Stabilizer link kit, DMCMW Illuminated door sills, Aussie Illuminated SS Shifter plate, GENUINE MOMO EVO Steering wheel, DELOREANA Extended View Side Mirrors w/ Heaters, DELOREANA LED Door Lights.

  8. #18
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by davidc89 View Post
    I have no clue what you are talking about, but I am definitely interested on this topic. Keep up the good work!
    It was my goal to reduce how hot the fan fail unit gets running high current (OEM) fans. I did reduce the power (total heat generated) but I did not take into account some of heat on the old fan fail unit was in the fuses and not getting transferred to the fan fail unit.

    Old fan fail generates 4.17 watts of heat at 30 amps (15 amps each fan). Case temp peaks at 141.4 deg. F

    New fan fail generates 2.88 watts of heat at 30 amps (15 amps each fan). Case temp peaks at 140.9 deg. F

    Not that the unit running at those temps will make if fail since all my components are rated to work above 185 deg. F. But assuming that 64 deg rise above ambient, if the relay compartment is above 120 deg. F that would bring the unit close to that 185 rating with a worst case of 15 amps on each fan.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  9. #19
    Senior Member Bitsyncmaster's Avatar
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    I tested the new and old units at 20 amps (10 amps each fan) and the new REV C peaked at 111.3 deg. F and the old peaked at 110.6 deg. F. I also ran the new one at 16 amps (8 amps each fan) which is the typical low power fan current. It peaked at 102.2 deg. F.

    I tested the unit in my car and made up a shorting plug to install into the harness at the fan connector.

    Passenger side pumped 125 amps for 14.5 ms.
    Drivers side pumped 125 amps for 15.0 ms.

    So as expected my solid state fuses are much faster than a standard fuse. They are also precise for the tripping. They will trip in well under one second at 18.2 amps.

    The fan on sequence was just a "freebee" since I had to install MOSFETs for the solid state fuses.

    I will be driving to a tech session in a few weeks and that 6 hours of driving will show bugs if there are any bugs in the "fan fail" light. I did not put any filters in the software for fan fail light driving but the current sensors have a pretty large capacitor filter on them. I have Toby fans in my car.

    It's a shame I did not get them to run cooler. I could get a little cooler if I go with 4 oz. copper on the circuit boards but that may never get done.
    Last edited by Bitsyncmaster; 09-11-2015 at 05:36 PM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #20
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    I installed a parallel jumper on the longest circuit board trace to reduce power (heat). What generates heat is the resistance of my current sensor (1.2 mil/ohm), MOSFET (1.0 mil/ohm) and the circuit board traces.

    So now the old REV B board generates 4.185 watts of heat and the new REV C board generates 2.43 watts of heat if each fan is drawing 15 amps (probably worst case). The potted side of the REV B unit stabilizes at 62.1 deg F above ambient. The potted side of the REV C unit stabilizes at 63.6 deg F above ambient. This just proves the fuses are dissipating a lot of heat and not transferring a lot of that heat into the unit.

    I'm going to start offering the REV C units for sale at $20 above the price of REV B units to cover the cost of the additional components. I've run the first unit for 6 hours driving my car with Toby fans. Only thing in question is if the other fans may produce more noise and may cause a random fan fail light flash. I hardware filtered the current sensors pretty heavy and have not added any software filtering.

    So the REV C units:
    1) Produce less heat
    2) Are not user programmable
    3) Have fixed 18 amp electronic fuses
    4) Will sequence the fans turning on with a 2 second delay on the second fan.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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