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Thread: Oil temp sensor vs. kitchen thermometer in heated oil

  1. #1

    Oil temp sensor vs. kitchen thermometer in heated oil

    My RV7A engine is showing low engine oil temperature in a new Lycoming IO_360-M1B with AFS3500EE. 130F at cruse. The spec sheet for engine oil temperature says the engine left the factory heating to 179F. Spoke to Lycoming, they suspect the probe. They suggested removing the probe and placing it in a beaker with heated engine oil with a standard kitchen thermometer and comparing temperatures. I used a simple electric griddle for the heat source. I recorded temperatures rising to 200 on the kitchen thermometer and temperatures falling back down after turning off the heat. I used, used automotive 10w30 engine oil. Any difference I think would be small. Below is the data I collected.

    I spoke to someone at AFS the other day on this issue, they said to check the grounding. The probe is grounded with safety wire to an engine bolt.

    Assuming the probe is not faulty and needs calibration, I see an adjustment for oil temperature under the administrative section. The next question is how much? I think setting it for accurate temperatures at 180 would be best. Rising temperatures at 180 were off by 60F on the EFIS, falling temps at 180 were off by 44F. Just guessing...start with an adjustment of 44?



    AFS Oil temperature sensor on EFIS 3500 vs. Kitchen thermometer in heated engine oil in degrees F.
    Rising temperatures

    EFIS/ Thermometer
    85 122
    88 130
    94 140
    103 150
    110 160
    115 170
    120 180
    124 190
    131 200
    137 205
    141 208

    Falling temperatures

    143 200
    140 190
    136 180
    132 170
    127 160
    122 150
    117 140
    110 130
    103 120
    Last edited by timotb; 04-14-2014 at 07:50 PM.

  2. #2
    Advanced Flight Systems Shawn McGinnis's Avatar
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    Quote Originally Posted by timotb View Post
    ...low engine oil temperature...
    The rate of change is a major factor in verifying any calibrated system. Ensure your achieving stable temperatures before you take a data point.

    Some diagnostics that may help oil temperature readings:

    1. Disconnect Engine Sensor Main Cable Pin 7 (Wht/Brn)
      • Screen should read AD_VALUE ~4095 and ~ -5.5 degF

    2. Connect Engine Sensor Main Cable Pin 7 (Wht/Brn) to Ground
      • Screen should read AD_VALUE ~0 and ~340.0 degF

    3. Connect Engine Sensor Main Cable Pin 7 (Wht/Brn) to 1KΩ Resistor through to Ground
      • Screen should read AD_VALUE ~2225 and ~65.0 degF


    Looking at your measured table your average deviation would be a +34.5 degF adjust.
    Shawn McGinnis

    Advanced Flight Systems
    support@advanced-flight-systems.com

  3. #3
    The temperatures were not stable during the rising and falling temperature test. The EFIS probe was lagging. Should I take another test reading trying to maintain a constant temperature, say 180 over 5 or 10 minutes?
    Regarding step 3. Pin 7 is the main wire on top of sensor. You want the resistor inserted there? "through to ground" is confusing. Then do the calibration adjustment +34.5 to correct for error?

  4. #4
    Advanced Flight Systems Shawn McGinnis's Avatar
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    Quote Originally Posted by timotb View Post
    Should I take another test reading trying to maintain a constant temperature, say 180 over 5 or 10 minutes?
    Yes for calibration you would want a stable oil temperature for say 1 minute, measure, then +20degF, then stable 1min, measure.


    Quote Originally Posted by timotb View Post
    Regarding step 3... "through to ground" is confusing.
    Name:  Oil-Temp.jpg
Views: 794
Size:  19.5 KB

    Hope this helps.
    Shawn McGinnis

    Advanced Flight Systems
    support@advanced-flight-systems.com

  5. #5
    Yes it helps, but the probe/ sensor is not depicted.

  6. #6
    Have you looked at this:

    http://www.advanced-flight-systems.c...ouble-Shooting

    1. The safety wire is not a good ground, your need to tightly wrap a bare wire around the probe threads and connect it to a good ground to test it.
    2. Are you positive that you don't have a shift adjust value, item 10. Shift Adjust should be 0
    3. Enable Admin mode, code is 1010 and email a picture of your Oil Temp calibration table to info@advanced-flight-systems.com
    4. Are you positive that you have a 18ga ground wire tied to the EFIS case?
    5. Where are you grounding the probe doing the test?
    6. Is this our standard probe?
    Rob Hickman
    Advanced Flight Systems Inc.

  7. #7
    Quote Originally Posted by Rob Hickman View Post
    Have you looked at this:

    http://www.advanced-flight-systems.c...ouble-Shooting

    1. The safety wire is not a good ground, your need to tightly wrap a bare wire around the probe threads and connect it to a good ground to test it.
    2. Are you positive that you don't have a shift adjust value, item 10. Shift Adjust should be 0
    3. Enable Admin mode, code is 1010 and email a picture of your Oil Temp calibration table to info@advanced-flight-systems.com
    4. Are you positive that you have a 18ga ground wire tied to the EFIS case?
    5. Where are you grounding the probe doing the test?
    6. Is this our standard probe?
    I'm working through this list and the trouble shooting URL. Answers to questions to follow. Item #3 above referenced Admin mode and gives code 1010. I've been to administrative settings many times, never asked to input a code. Can I get more clarification?

  8. #8
    You are in ADMIN settings, NOT ADMIN mode.

    1. ADMIN Settings

    23. ADMIN Mode

    Use the knob to enter the code 1010 and then press select. This will enable you to see all the calibration values, DO NOT change any of the new visible values.
    Rob Hickman
    Advanced Flight Systems Inc.

  9. #9
    Quote Originally Posted by Rob Hickman View Post
    Have you looked at this:

    http://www.advanced-flight-systems.c...ouble-Shooting

    1. The safety wire is not a good ground, your need to tightly wrap a bare wire around the probe threads and connect it to a good ground to test it.
    2. Are you positive that you don't have a shift adjust value, item 10. Shift Adjust should be 0
    3. Enable Admin mode, code is 1010 and email a picture of your Oil Temp calibration table to info@advanced-flight-systems.com
    4. Are you positive that you have a 18ga ground wire tied to the EFIS case?
    5. Where are you grounding the probe doing the test?
    6. Is this our standard probe?


    I'm studying your troubleshooting URL now. I have 3 ground wires connected to back of AFS case. They are 18 gauge. Oil temperature probe is installed as per the manual which was a short tutorial. Shift adjust set to zero. Check email for jpg of oil temp sensor table. For test, I attached a safety wire to probe tightly, through holes and attached to my fire wall ground bracket bolt which also has a heavy cable attached from this bolt to engine bolt plate. See second email picture sent. Next step to check for resistance as per item 7 of troubleshooting URL.

    This probe was supplied from AFS.
    Last edited by timotb; 04-18-2014 at 05:36 PM.

  10. #10
    Went on a fourth flight today. Probe seems to be working showing temperatures above 140 and cruise temperature of about 173. I suspect I shook up the grounding when I removed the probe to test it. I assume I had a bad ground also during test. Hopefully the problem doesn't return. I'm happy now.

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