Just some readings from a new Bosch Coolant Temp sensor (88 16v scirocco)
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degrees C kOhms -20 11.20 -10 10.00 9 3.36 20 2.42 30 1.72 40 1.16 60 0.72 69 0.63 74 0.59
At 25C is appr. (2420 + 1720 ) *0.5 = 2070 Ohm, likely 2063 Ohm NTC.
so depending on your AREF you'll need 2063_256 or 2063_287 see EasyTherm
You asked on irc what NTC the default firwmare has. I checked. NTC's nominal value is the resistance at 25C. So I looked for the 25C point in the matfactor table of vems.hex:
- internal value for 25C = 25 * 1.8 + 32 F = 25 * 1.8 + 32 + 40 = 117 = 0x75
- vems.hex mat table (0x200 .. 0x2F0) 0x75 can be found at :100280007A7979787777767675747473727271701B
- 0x88 position
at :100280007A7979787777767675747473727271701B
Since the NTC makes a voltage divider with a 2700 Ohm (onboard) resistor, at 25C the NTC resistance is (proportional to) 0x88 when the 2700 Ohm is (proportional to) 256-0x87=0x78
This reads: 2700/0x78 * 0x88 = 3060 Ohm nominal value
You likely want to hexpatch your firmware for an NTC of lower nominal value (closer to your 2063 Ohm NTC). It takes 2 mins to download/unzip and 2 mins to parameter hexpatch.exe and 2 mins to upload new firmware. See EasyTherm