The link is a Sender+switch
The case is ground, 1 of the contacts is "W" which is a warning contact that closes to ground when the temperature exceeds 90C,
The other contact "G" is a resistive output, 282 ohms should read 40C, 22 Ohm should read 120C (For a temperature gauge)
on your gauge, shorting the sender wire to ground should make it swing to 120C, and open circuit should read 40C, There is more than 1 sender calibration, but this one should match most VDO gauges
Could you take a photo of the gauge / describe what the gauge is for, I repair these things, so may know whats going wrong,
E.g. for a boat, they sometimes have a seperate sender negative wire, and if left floating makes the gauge read wrong.