This is for ISL 425 and maybe the same or similar for the ISL 400.
The hydraulic hoses, Comatrol aluminum valve body and the coil are located above transmission.
Engineer Mike had the technical information.
Hydraulic Valve is a poppet-type pressure relieving valve HydroForce TS38-2102 ( check part# on valve). Berenson Fluid Power. It is infinitely adjustable in a prescribed range using a variable electric input.
The variable resistance 12 volt coil HydroForce 4303712 (check part# on coil). If you have a problem, I would replace coil first and see what happens. Hydra-Power Systems stocks coil.
How it works.
The valve is in high speed fan with engine off. When the engine starts, the fan goes to low speed controlled by the ECM to increase fan speed as needed.
There is a single wire temperature sensor located directly behind thermostat housing that sends reading to ECM.
Depending on the temperature, ECM Pin 13 which has no programmable parameters sends a pulse modulated signal through a white wire to the coil to increase fan speed as needed.
When my coil my coil quit working, I began having overheating problems as fan speed would not increase. When the temperature got up to 225 degrees the fan would come on. I cut white wire to coil, put toggle switch mounted on dash to complete circuit to run on high. I could control my temperature manually fine. Do not apply any current to the white wire, only complete circuit. This told me everything worked except the coil.
When I replaced the coil on mine, it helped the overheating.
Marvin, you can PM me for more information
2007 Apex MDTS (425 hp) #75723
2007 Toyota 4-Runner
2014 Ram Laramie 3500