Ford 1510 temp sensor

[double hunter]

New to me Ford 1510, I have a question about the water temp indicator light, with the key in the on position is the temp. light supposed to be on, the batt and oil lights come on but not the temp light, I can take the lead off the sending unit and ground it and the light comes on, does this mean the sending unit is bad, any help appreciated.

 

[jinman]

Your temp light is working correctly. It is not supposed to be on unless the tractor overheats. It's a WARNING light. Not being on says the temperature is within range. The temperature probe is a thermal resistor (thermistor). It has high resistance when the coolant is at the proper temperature and decreases toward zero as the water heats up. You simulated that by grounding the wire and the light came on.

Your battery and oil lights come on because the battery is being discharged before the engine is running and the oil pressure is zero. They are also warning lights, but in their case, before you start the engine they sense problems. Once the engine starts, the alternator starts charging the battery and the oil pump puts out pressure, so both the lights go out.

 

[JC-jetro]

You can also verify the sending unit resistance cold VS operating temp. The sending unit can also be removed and partially immersed in boiling water to test. I'm not 100% sure on yours but they do have bi-metal heat sensor that they make or break at certain temp (calibrated ) that could run a bulb or a buzzer. "Off" being when the connection is broken and "on" when the connection is made.

if Your temp sending unit is purely resistive you can use numbers below for reference. I got data below testing my Ford 1700.

JC,

I do like the combination of analog gauge and "idiot light" but never light alone. Just imagine what happens if you have a burned out bulb.


Cold: sender=690 ohms, T housing = 98 , Radiator= 98 , Head=98 , Exh Man=98

Operating temp: sender=140 ohms, T housing = 172 , Radiator=170 , Head=174 , Exh Man=192


1/8" , right of middle: sender=92 ohms, T housing = 196 , Radiator= 196 , Head= 197 , Exh Man=210

Hot
1/8" left of H: sender=66 ohms, T housing = 210 , Radiator= 210 , Head=212 , Exh Man=250

 

[double hunter]

Thanks for the info, I thought that on a tractor I had in the past that all 3 lights came on when the key was turned on but not in the cranking mode, I was pretty sure the batt. and oil pressure lights were operating correctly, the temp lite had me concerned but it makes sense that it would not opearte unless running hot.

 

[JC-jetro]

Thanks for the info, I thought that on a tractor I had in the past that all 3 lights came on when the key was turned on but not in the cranking mode, I was pretty sure the batt. and oil pressure lights were operating correctly, the temp lite had me concerned but it makes sense that it would not opearte unless running hot.

I would suggest that you make sure change of state happens from cold to hot with the sender still on the tractor. Having a non contact infra red thermometer is excellent for checking things out. if your sender unit is make or break variety you will not know overheating and when you know it might be too late.if you have ohm meter use it and see if resistance change happens between cold and operating temp. On/Off switch like oil sending unit is normally closed so it completes the circuit when the key switch is on. upon engine start the pressure opens up the switch so the light stops illuminating. In this setup complete circuit is verified first and then action of sending unit as well.

JC,