Radiator Cooling Fan not working

[Monte Barber]

The Fan Mounted behind the Radiator is not coming on and Motor overheats. What controls the fan? It has several Hoses hooked
to it like it runs off of Pressure?? Has anybody had theirs replaced? I have a 2002 Patriot with the c-12 Cat.

[Edward Buker]

Monte,

There is a unit called a wax valve that regulates the hydraulic oil flow through the fan hydraulic motor. There may also be an activation temperature sensor circuit that signals the valve to open but I am not overly familiar with how this system works. I think Lee and Gerald have more insight then I do on how this system functions and can take it from here when they get a chance. I do know that getting a wax valve can have a long lead time if you cannot find one in the states.

Later Ed

[Gerald Farris]

Monte,
Here is how your cooling fan works. It is a hydraulic motor that is drive by the same pump that powers your power steering system. The hydraulic pressure is controlled by a wax valve located in the coolant flow as it leaves the radiator.

Since you did not mention a power steering issue, we will assume the hydraulic system is operating normally. That leaves the fan motor or wax valve as the problem. However, the most common problem that causes a fan operation problem on your model coach is a low coolant level. The wax valve does not operate properly unless it is emerged in coolant, so a low coolant level can cause an inoperative fan. If you are certain that your coolant is full, since the fan motor and wax valve are both expensive parts, you should probably get the system diagnosed by an experienced mechanic before you start throwing parts at it. 

Gerald   

[Dave Atherton]

Monte, you indicated your fan stopped working, working slow heating up. Gearld pretty much
covered the operation of the Wax valve operation. Let's go down to the hyd pump that provides
the pressure and flow to both the steering and fan motor operation. Your hydraulic pump has
a sequence valve or shifter hydraulic spool that is on the pressure discharge of pump. It is very
possible the sequence valve is partly stuck allowing hyd flow the steering and is not providing
enough hydraulic flow to operate the fan motor. ( note: the steering and brakes require less
or operate than a hydraulic operated fan motor. ) I would suggest first check the steering sector
housing for excess heating than check the end of the hydraulic pump for excess heat and fan
motor, this should bring you back to the hydraulic pump with possible sequence valve partly
stuck. Last thing you should check,three hydraulic lines coming off fan motor ( there will two lines the
same size going in and coming out of hydraulic motor. Than a smaller line coming off the center
body of hydraulic motor ). Take off small line and run engine there should be very little hydraulic
fluid coming out this line, this is what called Case Drain and if lot of fluid comes out at this point
than your hydraulic fan motor is bad and will need to be replaced.This will complete your Hydraulic
fan operation. Dave Atherton Retired Cat Mechanic