Mechanical slip failsafe system for a heavy duty multi-speed fan clutch

A control system for a hydraulically controlled fan clutch system, said control system comprising:

• (a) a base mounting member;
• (b) a housing assembly rotatably connected to said base mounting member and containing a fluid, said housing assembly connected to a pulley member for rotating at input speed;
• (c) an output member rotatably positioned relative to said housing assembly;
• (d) a cooling fan member attached to said output member;
• (e) a wet clutch pack in said housing assembly, said wet clutch pack positioned between said housing assembly and said output member and dependent upon pressure of the fluid for selectively rotating said output member and said fan member;
• (f) an axial extending valve assembly positioned in said base mounting member for controlling the amount of fluid being transmitted to said wet clutch pack;
• (g) a controller with an electric coil for electronically controlling the flow of fluid into said valve assembly;
• said controller operable to control the flow of fluid by the amount of magnetic flux created by said electric coil;
• (h) a temperature control mechanism in said valve assembly for selectively preventing flow of fluid through said valve assembly when the temperature of said fluid exceeds a predetermined temperature level;
• and
• (j) a fluid pressure relief mechanism operable to allow escape of at least a portion of said fluid at a predetermined fluid pressure level.