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Thread: Electronic Otterstat

  1. #21
    Voice For Hire Farrar's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    I do like the idea of removing the OEM otterstat and using a straight pipe so no chance of the otterstat leak or blow out.
    <off-topic>
    I'd have been happy with a threaded hole instead of the silly clamp thingy. I think that would reduce leak & blow-out. Screw-in switches have been used for years on other cars... But that would require a different pipe, I suppose. Surprised no vendor has offered this and a cross-referenced switch as an "upgrade."
    </off-topic>

    That said -- I'm a big fan (pun intended) of your work, Dave, and will follow this project with interest!
    DeLorean status: probation

    "Our doubts are traitors,
    And make us lose the good we oft might win
    By fearing to attempt."
    -Wm. Shakespeare, Measure for Measure

  2. #22
    Senior Member BABIS's Avatar
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    Quote Originally Posted by Farrar View Post
    <off-topic>
    I'd have been happy with a threaded hole instead of the silly clamp thingy. I think that would reduce leak & blow-out. Screw-in switches have been used for years on other cars... But that would require a different pipe, I suppose. Surprised no vendor has offered this and a cross-referenced switch as an "upgrade."
    </off-topic>

    That said -- I'm a big fan (pun intended) of your work, Dave, and will follow this project with interest!
    this may be the one you need: https://www.deloreango.com/it/new-st...otterstat.html
    VIN 4502

  3. #23
    Voice For Hire Farrar's Avatar
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    Quote Originally Posted by BABIS View Post
    Ooh, shiny! Thanks -- I didn't know that was even a thing.
    DeLorean status: probation

    "Our doubts are traitors,
    And make us lose the good we oft might win
    By fearing to attempt."
    -Wm. Shakespeare, Measure for Measure

  4. #24
    Senior Member mr_maxime's Avatar
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    Lol that's exactly what I was asking about and got Dave to start working on this.

    I can't tell on mobile but the one I found was in the UK and I wanted to make sure it used NPT threads so that it would work with universal cooling fan switches in the us.

  5. #25
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    My VIN:    03572

    I finally got caught up on low inventory building. So I did a little checking of the stock temperature gauge sensor circuit. Car gauges compensate for voltage variations so I'm working a way to do the same when I use that circuit for my electronic otterstat. Anyway, I tested the sensor (I assume mine is original).

    Engine off sitting at 74 deg. F the sensor reads 2.69 Kohms.
    Temp gauge at 1/8 scale (needle between the first and second marks) the sensor reads 283 ohms.
    Temp gauge a little below the 1/4 mark is where my thermostat opens, the sensor reads about 230 ohms.
    Waited a long time for the fans to kick on gauge about one needle width above the 1/4 mark, sensor reads 160 ohms.

    Also measured the current in that circuit when the fans kicked on at about 70 ma.

    Voltage on that circuit measured to ground is 14.1 volts cold, 11.7 volts at 1/8 mark, 10.6 volts at 1/4 mark.

    Voltage on that circuit measured to cars "12 volts" was 3.02 volts engine off but heated to the 1/4 mark. With engine on it was 3.77 volts. So using car voltage referenced to the gauge circuit is not perfect. I will probably be measuring the car voltage along with the sensor voltage and have software tables do the correction.
    Last edited by Bitsyncmaster; 06-06-2017 at 08:16 PM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  6. #26
    Senior Member Bitsyncmaster's Avatar
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    I wired my red relay socket for the electronic otterstat. I'm going to make up a new circuit board and order one protype board for testing and debugging. Using the dash gauge temp circuit I only need four pins in the socket.

    Pin 85 ground.
    Pin 86 voltage from fuse #5 which is the same power used for the dash gauges and the otterstat.
    Pin 30 is tapped onto the temp gauge sensor. (Green/blue wire in relay harness).
    pin 87 will be the output. Plan to just tap onto the existing otterstat wire. Not sure if I need a diode yet but don't think so.

    There are many green wires in the relay bank harness. I had to lift my fuse block to find the correct green wire going to fuse #5. I also found a cut green wire but not sure if I did that or it's just for the auto transmission circuits.

    I don't think any radios have a mute signal input. If they did, I could use the extra pin for that to mute the radio if I signal an over temp condition. By the way, that gauge sender seems to respond very quickly to engine warming up.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  7. #27
    Senior Member Bitsyncmaster's Avatar
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    Was just thinking about my software for checking for a sudden voltage drop to warn the driver since that often means the alternator belt has failed (stops your water pump). So to prevent the warning when the engine shuts off, I'm changing the power source for my "electronic otterstat" to the RPM relay output (second output that drives lambda).

    I was thinking it's best to use the same power source as the temp gauge but that is powered even with the engine stopped.

    So my electronic otterstat can be used for:

    1) Just an audible warning device. Engine overtemp and or alternator failure.
    2) A backup for the standard otterstat failure. Redundant otterstats powering the fan relay.
    3) Eliminating the standard otterstat.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  8. #28
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    My VIN:    03572

    I got my "bare bones" circuit board. I assembled it and started writing software. I ordered a decade adjustable resistor so I can simulate the function of the temperature gauge circuit on the bench. I did a quick check of the sensor before and I posted those results but I really need precise readings.

    The gauge drives the sensor through a coil of wire in the gauge. That coil has a cold resistance of 54.13 ohms.

    When I get my decade resistor box I will replace the sensor with that box so I can get precise resistance values which the gauge shows 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8, and full scale. Not that I need to know all those values but it will be good info.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  9. #29
    Senior Member
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    How can I help? I'm sorry, I don't understand what info you are looking for.

    Need to remove temp sensor and test output resistance against temperature? I'm not going to do that to my car, but if I have misunderstood and can test something else then please let met know.

    Mark

  10. #30
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by Horsebox View Post
    How can I help? I'm sorry, I don't understand what info you are looking for.

    Need to remove temp sensor and test output resistance against temperature? I'm not going to do that to my car, but if I have misunderstood and can test something else then please let met know.

    Mark
    Thanks. I have not thought of anything I can not test myself yet. I just pull the pin on the bulkhead connector to open the circuit for the temperature gauge. What I'm going to do is get resistance values for temperature gauge readings that are above what my car gets. My car never shows much above the 1/4 mark on the temperature gauge. I'm hoping this data can help some owners check why their gauge shows higher normal temps then other owners. So is the difference the gauge, sensor or something else.

    My otterstat unit will have user adjustable trip points anyway. I have eight switches (a DIP switch) so if all 8 are used to set the "trip" value that gives 256 adjustments. I will probably use some switches for other adjustments. I know I need to have a test mode so the owner can hear the alarm (buzzer) just to know what is sounds like and how loud it is.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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