Replaced coolant temp sending unit do you need to recalibrate the gauge? | FerrariChat
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Replaced coolant temp sending unit do you need to recalibrate the gauge?

Discussion in 'Technical Q&A' started by 308GTS, Apr 28, 2006.

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  1. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,223
    TN
    #1 308GTS, Apr 28, 2006
    I replaced the coolant temp sending unit in my 85 308. I read in the archives that you need to have the coolant temp gauge recalibrated if you replace this part. Is this true? I would think that the sending units that T. Rutlands sell should work with the stock gauge without sending the gauge off to be recalibrated. Any info would be appreicated. Thanks.
     
  2. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    #2 Steve King, Apr 29, 2006
    Never heard of doing that. Just put in the new sender and it should be good to go. Enjoy the ride
     
  3. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,223
    TN
    #3 308GTS, Apr 29, 2006
    Thanks. I appreciate it.
     
  4. Sloan83qv

    Sloan83qv F1 Rookie
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    #4 Sloan83qv, Apr 29, 2006
    Had to recalibrate when I did mine.....was off 30 degree's.
    Use a IR Temp Gun to verify

    Has nothing to do with supplier, I tried a new one and a used one and had differences with both.
     
  5. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    #5 Steve King, Apr 29, 2006
    Martin so how did you get the IR reading. Did you measure multiple points on the block and take the avg. number. Also how did you claibrate the IR gun. I would suggest that the temp range across the engine at different points will vary 30* or more due to different conditions and air flow . These gages are most likely only good for +/- 5* and I don't think you can get the IR gun pointed at the location of the tem sending unit to get a somewhat accurate measurement. I only use the IR for looking at potential hot spots and targeting a problem area. I get it calibrated once a year and over the last 3 years it usually stays in the +/- 2* range. Enjoy the ride
     
  6. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,223
    TN
    #6 308GTS, Apr 29, 2006
    I have had the same problems with IR temp guns. My gauge seems to be reading high especially compared to my temp gun. However, my temp gun tends to fluctuate on readings. Like Paul I installed a new temp sending unit and my gauge seems to read a little higher now. That is why I was wondering they need to be calibrated accordingly.

    What resistance have you guys taken at the sending unit when the coolant temp is 195?

    I can't get to the sending unit with my gun but I shoot the thermostat housing and the aluminum coolant pipe by the oil filter as well as rad. inlet and outlet. .
     
  7. Sloan83qv

    Sloan83qv F1 Rookie
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    #7 Sloan83qv, Apr 29, 2006
    Its not the IR Temp Gun.

    I have tested the accuracy of the gun using a candy thermometer and the gun is accurate, I have also used the gun to monitor the on and off function of the fans and it is right on the money with the fan switch rating.

    Call Palo Alto Speedometer and they will tell you that they calibrate them all the time.

    Best place to take measurement on 308 is at the sending unit mount location as well as at coolant tube beside oil filter as those two places should read what guage is reading....the thermostat housing should not be the place you take temp reading to compare to guage.
     
  8. bill308

    bill308 Formula 3
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    #8 bill308, Apr 29, 2006
    Don't forget the surface finish you are looking at can have a significant effect on the temperature the IR gun sees. Shiny aluminum has a low emissivity (low radiation) so will look cooler to the IR gun. If the target is polished, you will likely see the reflection of surrounding surfaces and measure their temperature. Most painted surfaces have a high emissivity (~ 0.9) so one will likely get a very accurate reading.

    Bill
     

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