Thermal Sender/Coolant Sensor Question on SR20

[MrIllegalX]

I've done a little research, and want to know if any of you guys think this is right. On my Sr20, my autometer temp. gauge will say then engine is 125 deg. when the engine really is 180 (determined by a temp. gun) and on the stock gauge cluster temp. gauge never goes above the 2nd line. My idle is also slighly speratic at times, and always idles around 1,500 RPMs.

With some help I narrowed it down to the thermal sender. I went to the dealership and purchased this part (for a 89 240) not realizing that oh, I don't have an 89 240 engine, I have a Sr20.

So will it still work and do you also think that could be the problem? Thanks.