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Temp gage

Discussion in '308/328' started by LE06, May 17, 2025 at 4:15 PM.

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  1. LE06

    LE06 Karting
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    #1 LE06, May 17, 2025 at 4:15 PM
    I refilled my cooling system today after flushing it and replaced the thermostat and temp sensor on the radiator. I made sure all the air was out of the system about 3 times. The temp got to 220 and stayed, I checked for air but it was good. Another test drive and same results. I decided to check the temp with my temp gun. Every where I pointed it would read from 170 top 175, between the V it read 185. The inlet of the radiator was 175 the exert was much cooler. I decided to crank it and let it idle. The car gage stayed at 220 and around 225 the fans kicked on. Several times and places I checked the temp it always read around 180. I took it for a drive and the temp stayed around 220. When I cut the car off the gage goes down to 150 ish. Should the gage die like the others? Could I have a bad temp sensor?

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  2. LE06

    LE06 Karting
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    #2 LE06, May 17, 2025 at 4:25 PM
    After posting I read on Birdman’s sight you should drill a small hole in the thermostat. My old one did not have a hole so I don’t think that is the problem. Maybe Monday I will pull it out and drill and reinstall,
     
  3. mk e

    mk e F1 World Champ

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    #3 mk e, May 17, 2025 at 6:08 PM
    The fan switch it 195 I think? So you gage does seem to be reading high.

    A small hole in the tstat means a little circulation all the time so slower warmup but can make it easier to get all the air out I guess.

    Did I read you have efi? If so, what is that saying?
     
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  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #4 Steve Magnusson, May 17, 2025 at 9:20 PM
    The temp sensor (104628) for the water temp gauge in the dash is located in the coolant crossover pipe (not the radiator) -- item 35 here:

    https://www.ferrariparts.co.uk/diagram/ferrari/308-gtb-gts-usa/021-water-pump-and-pipings

    If you do a search on that part number "104628", you should get some prior threads that have the resistance vs temperature data for that sensor so you can do some sanity checks on that sensor. I'd suspect the 104628 sensor being wonky before the gauge in the dash (still could be the gauge in the dash, but easier to first measure, or replace, the 104628 sensor than mess with the gauge in the dash IMO).
     
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  5. LE06

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    #5 LE06, May 18, 2025 at 8:15 AM
    All I have is a cheep laser temp gun. But it has always been dead on. When the fans turned on the sensor was around 190 ish according to my hand held gun.
    I don't know if it’s worth drilling a little hole or not. I am pretty sure I have all the air out.
     
  6. LE06

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    #6 LE06, May 18, 2025 at 8:18 AM
    Thank you. Checking the resistance is a great idea. The only reason I suspected the gage is because with the key off it does not completely die
     
  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #7 Steve Magnusson, May 18, 2025 at 8:28 AM
    Yes, that is a bad sign for the gauge itself (I didn't read carefully enough).
     
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  8. ferrariowner

    ferrariowner Formula 3

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    #8 ferrariowner, May 18, 2025 at 10:35 AM
    Turn on your headlights and see if the gauge reading changes (goes up). Then clean up your ground connections.
     
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  9. detroiter

    detroiter Karting

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    #9 detroiter, May 18, 2025 at 1:45 PM
    If I am not mistaken, there is a multipin electrical connector on the driver's side of the engine that you can open to measure the resistance of the sensor fairly easily.
     
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  10. LE06

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    #10 LE06, May 18, 2025 at 5:46 PM
    I tried your tip. When I turned the key on the gage went to 0. Head lights on makes no change. I turned the key off and the gage went back up to where it is in the picture. AC lies, DC dies……..This seems odd behavior
     
  11. ferrariowner

    ferrariowner Formula 3

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    #11 ferrariowner, May 18, 2025 at 5:48 PM
    If you can reach the wire at the sending unit, unplug it. The gauge should go to 0. If so, bad sending unit.
     
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  12. LE06

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    #12 LE06, May 18, 2025 at 6:35 PM
    Ok will do. I can get to it the carbs are about to come off for a rebuild.
     
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  13. ferrariowner

    ferrariowner Formula 3

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    #13 ferrariowner, May 18, 2025 at 7:13 PM
    Ground it should peg the meter.
     
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