OK so I found out that the proportioning valve controls the fan speed by regulating the amount of hydraulic fluid flow through the fan drive motor. I had the fan drive motor rebuilt earlier this year and has worked fine until the hot weather. Now the fan won't speed up (like it used to) when the temperature guage climbs closer to the yellow then it ever has before. Before the fan would speed up before it reached the point it climbs to now.
According to the attached document the proportioning valve is controlled by the input of both the hydraulic temperature sensor and the coolant temperature sensor.
I tried disconnecting the hydraulic temp sensor and a red hydraulic temperature light came on, but no change in the fan speed running hot at full rpm. So that sensor must be working?
I tried disconnecting the coolant temp sensor and a red coolant temperature light came on, but no change in the fan speed running hot at full rpm. Also the temperature guage didn't work when disconnected. So that sensor must be working?
I read somewhere that if you disconnect the coil that fits over the proportioning valve then the fan drive will operate at full speed as a default. I tried this and it only runs at a medium speed not the full high speed that I remember it kicking into on hot days.
I bought a new coil and installed it and no high fan kick in at higher than normal temperatures like it used to.
I took out the proportioning valve and found out the default position is closed. I cleaned it out with WD-40 in case it was stuck. The valve is under spring tension and opens and closes with ease. It's basically a solenoid, very simple. Using a small drill bit I could easily push open the valve completely and it would spring back shut.
If I start the COLD engine with coil disconnected then the cooling fan spins at medium speed at full rpm. So there is some type of default flow, but I heard it should be full flow. Any thoughts?
If I connect the coil with COLD engine then it doesn't spin until engine reaches normal operating range, which it should do. So the coil must be functioning, I realize now my old coil was probably fine.
The proportioning valve must be working to some degree as well but for some reason when the temperature climbs higher than normal, the proportioning valve isn't fully opening when it should.
My thoughts are:
- Is the hydraulic temperature sensor shot? (Doesn't seem like it with above test)
- Is the coolant temperature sensor shot? (Doesn't seem like it with above test)
- The coil isn't shot because its brand new
- Is the main controller or computer not sending enough voltage to the proportioning valve and thus not opening fully? If so then why isn't the proportioning valve running at full speed when disconnected?
- Is the proportioning valve shot somehow, even though when I took it apart it opened freely.
Any thoughts or help would be much appreciated!
