Re: Temp sending Unit

Posted by HH56 On 2011/1/23 21:09:47

The resistance in the sender you are reading is the heater wire. You are correct in that it is an on/off cycle. Works exactly the same way the instrument voltage regulator does on the later units.

When on, both heaters are in series and start to heat. The bimetal in gauge begins to move and the bimetal in the sender does also. At a point the sender bends enough to open the contact and both units cool down. Gauge moves slowly in reverse a tiny bit when sender opens but as it moves slowly, the movement is almost not seen. Sender cools down too, cycles and re establishes contact and starts heating again. This on/off repeats at a rate until gauge reads the actual temp and stabilizes. At that point its a rapid on/off to keep the needle almost immobile. As the engine heats, it also acts on the bimetal and changes the cycle time which is reflected in the gauge reading. Gas gauge is also similar in operation except the float works a mechanical cam which applies force against that bimetal and changes cycle rate.


That off cycle is the part I don't know about. Maybe you could heat some water to about 160 degrees. Hook up the 53 sender and watch the needle. If it goes to mid point or appropriate area and stays, maybe it would work. If it keeps trying to move past that point, disconnect it before any damage occurs.