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Thread: New Fan Fail relay

  1. #51
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,845

    My VIN:    03572

    The new fused fan fail unit is now ready for sale. I did a bench test with two OEM fans and a static car test in my car with Toby fans. My car is still down waiting for a new clutch so no driving testing yet. Fans get directly powered via a 20 amp fuse on each fan so the only thing I was really testing is that the fan fail light worked without any glitch.

    I have four units with the paint dry now but I had promised 3 of those to customers. I will paint another four today and have started another build of 10.

    I've priced the unit at $84 including USA shipping. By the way USPS just increased prices again.

    I've updated my web site. I have not removed the electronic fused NLA info yet in case some users still need the instructions.

    History:
    Revision A fused fan fails running 40 amps. (20 amps each fan) dissipate 9.68 watts.
    Revision K fused fan fails running 40 amps. (20 amps each fan) dissipate 5.45 watts.
    Revision I electronic fused fan fails running 39 amps. (19.5 amps each fan) dissipate 2.58 watts. Had to drop the test current since these fuse at 20 amps.

    So you can see why I tried to use electronic fused fan fails but each owner's fans are so different it just caused to many problems. Now no one should keep running fans that draw 40 amps of power because the stock wiring is just not designed for that current.
    Last edited by Bitsyncmaster; 02-17-2018 at 10:19 AM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  2. #52
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,845

    My VIN:    03572

    I ran a temperature test on my latest fan fail unit (REV M). My "hot plate" maxed out at 200 deg. F but the air temp maxed out at 171 deg. F. So I was running 10 amps through each fan output and after 15 minuets it flashed the overheat (three flash sequence). I shut of the hot plate and 7 minutes later the overheat warning shut off, air temp was 147 deg. F.

    My temp sensor is rated at one deg. C accuracy and software turns the overtemp warning on at 85 deg. C and above.

    One thing some customers are getting is a double flash which indicates both fans have 10 volts or less on the outputs to the fans. Some are confusing this as the overtemp warning but it's a warning of a connection problem that the fan fail is getting 10 volts or less on the input power. It could also indicate both fuses have blown but everyone says both fan are running.

    Now due to the fuse generating heat if your fans draw more than 10 amps each the overheat warning will come on at a lower fuse box temperature. I can run that test later with 15 amps each which is what the OEM fans can run at.

    I plan to order some heat sinks for my test bed so it brings the air temp up closer to the hot plate temperature.

    I can load test now any relay up to 60 amps. I run a fan on my resistor loads when doing extended high current testing.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  3. #53
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,845

    My VIN:    03572

    I tested another REV M fan fail.

    I got a massive heat sink to sit on my hot plate. It still only brought the air temp up to 180 deg. F (82 deg. C). That is still a little shy of my 85 deg.C trigger and the overtemp did not kick on till I ran 10 amps on each fan load for 11 min. Now it did cool down a lot slower and the overtemp turned off at 156 deg. F.

    I was just thinking what could be different in that temp testing as seen in the relay compartment. I thought of one thing in that the wires going to fan fail socket are only a few inches long in the heat box so maybe some heat is dissipated though the wires exiting the box. Also the fan fail unit is upside down but I would think that would be worse testing since the fuses are what generate the most heat and heat rises.

    I'm thinking the turn off temp is the point that you may get a fan fail overtemp warning after a very long drive with the AC on.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #54
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,845

    My VIN:    03572

    I mounted a vertical plate on my heat sink so I could bolt the relay test socket pointing up an leave 12 inches of the wiring to that socket in my heat box. Big change in that the overheating fan fail would not shut off the warning until the air temp dropped to 131 deg. F. I'm assuming with my first tests the fact the wiring was exiting the box very near the socket made a heat sink removing heat from the fan fail unit. Now my test closely resembles what the unit sees in the DeLorean fuse box.

    My hot plate maxed out at 207 deg. F
    The air temp at that max was 190 deg. F Still did not turn on my overheat warning.
    Turned on the dual 10 amp loads and the overheat warning came on in 60 seconds at 192 deg. F air temp.
    Overheat stayed flashing until the air temp dropped to 131 deg. F

    Note it took my hot plate 2 hours and 15 minuets to reach the max temp so the fan fail must have been very close to the 190 deg. F air temp.

    I think I can improve my hot plate by placing some insulator under the top plate so the box with the electronics does not heatup the same as the hot plate. I'm thinking that will speed up the heating and also increase the max temp.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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