How do I find a temp sending unit for a 150-300 degree gauge?

I need to find a temp sending unit for a 150-300 degree sweep gauge. Any ideas on how I go about this?

 

What brand of gague

 

You need to match the gauge to the sending unit, i.e. Autometer to Autometer
and the for the calibration of the temperature sender to the gauge.

 

The gauge is an oddball NOS item, no real chance of buying the proper sending unit to match....

 

It is my understanding that most non mechanical gauges that use sending units are converting the information they read to a varying range of ohms of resistance.
As an example your gauge could require a resistance of 50 ohms from the sending unit to read 150 degrees and 300 ohms to read 300 degrees. The point being is you need to match the ohm range of the sender to the range of the gauge. If the sender and gauge are not matched you may get inaccurate readings backwards reading or none at all. I believe you should focus on the ohm range of the gauge more than the temp readings that it reads.I believe your key is to find the ohm range of your gauge.

 

I would recommend testing whatever gauge you have with a variable resistance tool and looking in the Echlin catalog specifications chart to figure out what sender might work. Keep in mind that factory calibration is +/- 10% and the senders are the same. Thus, even with a good gauge and sender you can be 20% off out of the box.