Cooling Fan does not cycle

[Tom and Pam Brown]

Cooling fan does not turn off or cycle.  

Anyone have a idea where I should start my investigation?

I am familiar with on/off fans on trucks but this hydraulic fan is throwing me a curve.

Relay, temp sending unit or other components of the system i should look for?

Thanks

[Richard And Babs Ames]

http://forum.bacrallies.com/m-1277944745/s-27/highlight-hydraulic+fan/#num27 is a discussion of a leak but some good pictures and a parts source in GA. Will ask my mechanic at chruch as he used to build full hydraulic systems. The fan has severl pressures (speeds) it operates at and may may take some enginerrring to fix as direct replacement parts are not readily available.

[Tom and Pam Brown]

There is no leak.  It seems to be locked up, in the on position.

Tom

[Richard And Babs Ames]

Understand no leak. Pictures are of control switch and related items.