Cat 257B hydraulic fan cutting off

[gTrees$]

Is there a sensor somewhere that would cause this to be happening. Hydraulic fan cutting off

 

[oldnslo]

I suspect that fan runs on a temperature sensor but I have no clue where it is located. Is there a separate fan for engine cooling or the same fan?

 

[Doaaj50]

Typically proportional hydraulic fans have a “fail full on” logic in the design. This means that if the power is cut to the proportional control valve, it will default to full fan speed. If you can find the proportional valve that controls the fan, unplug the electrical connector and see if you get full fan speed. If so, then it will lead you towards an electrical issue. If it doesn’t, then it would be something hydraulic. Most likely you have a sensor that is failing but this simple test will help verify that a sensor is the culprit.