For the hardy types who still have hydraulic HICAS in their machines...

Ocassionally on a run, the HICAS warning light came on and stayed on. Steering function remained normal and the fluid level was ok and on a re-start, after say five minutes, light operation returned to normal - for a while. Conzult provided no clues either.

The HICAS sensor is basicaly a magnetically actuated reed switch which is located at the lower end of the tube attached to the bottom of the reservoir cap. The metallic sleeve at the centre of the float is a magnet, which if maintained above the level of the reed switch will not cause the reed contacts to close and consequently turn on the HICAS warning light. With the engine running there is a lot of turbulence in the HICAS reservoir and the fluid gets hot. To shield the float/magnet from the turbulent flow, a plastic sleeve incorporating fine mesh 'windows' is fitted to the neck of the reservoir. Normally the float should move freely within the sleeve. However over time and with perpetual temperature cycling, what was a loose fit between sleeve and float becomes an irregular interference fit, causing the float to jam. As the ATF fluid heats up the float expands, so does the sleeve and more significantly, so does the distortion of the porous fine mesh. Also with age, fluid has permeated into the float, affecting its buoyancy and expansion characteristics.

So much for the 'theory'. So how to eliminate the possibility of the float becoming jammed. Smoothly shaving off sufficient material from the diameter of the float turns out to be easily over done, quickly rewarded by a float that doesn't and a permanent warning light. Then try buying a replacement float. About now disconnecting the sensor starts to look attractive. Leaving the sleeve out altogether removes the likelihood of jamming but would expose the float to the full maelstrom in the reservoir and the possibility of an even more annoying rapidly blinking HICAS light. Don't know about this, didn't actually try it as I was on my last sensor/float combo. Trying to permanently slightly distort the shape of the sleeve by applying heat was binned, given that the sleeve lives in hot fluid.

As a final resort I cut out the distorted fine mesh windows in the plastic sleeve. This retained the essence of what Nissan orinally intended and it actually works, reliably. Not sure of the real residual benefit of retaining the meshless sleeve, but I don't get that annoying light, steady or blinking, other than when it is supposed to work. Hope this is some help.

Edited June 22, 20196 yr by tandyn300

For the hardy types who still have hydraulic HICAS in their machines...

Ocassionally on a run, the HICAS warning light came on and stayed on. Steering function remained normal and the fluid level was ok and on a re-start, after say five minutes, light operation returned to normal - for a while. Conzult provided no clues either.

The HICAS sensor is basicaly a magnetically actuated reed switch which is located at the lower end of the tube attached to the bottom of the reservoir cap. The metallic sleeve at the centre of the float is a magnet, which if maintained above the level of the reed switch will not cause the reed contacts to close and consequently turn on the HICAS warning light. With the engine running there is a lot of turbulence in the HICAS reservoir and the fluid gets hot. To shield the float/magnet from the turbulent flow, a plastic sleeve incorporating fine mesh 'windows' is fitted to the neck of the reservoir. Normally the float should move freely within the sleeve. However over time and with perpetual temperature cycling, what was a loose fit between sleeve and float becomes an irregular interference fit, causing the float to jam. As the ATF fluid heats up the float expands, so does the sleeve and more significantly, so does the distortion of the porous fine mesh. Also with age, fluid has permeated into the float, affecting its buoyancy and expansion characteristics.

So much for the 'theory'. So how to eliminate the possibility of the float becoming jammed. Smoothly shaving off sufficient material from the diameter of the float turns out to be easily over done, quickly rewarded by a float that doesn't and a permanent warning light. Then try buying a replacement float. About now disconnecting the sensor starts to look attractive. Leaving the sleeve out altogether removes the likelihood of jamming but would expose the float to the full maelstrom in the reservoir and the possibility of an even more annoying rapidly blinking HICAS light. Don't know about this, didn't actually try it as I was on my last sensor/float combo. Trying to permanently slightly distort the shape of the sleeve by applying heat was binned, given that the sleeve lives in hot fluid

As a final resort I cut out the distorted fine mesh windows in the plastic sleeve. This retained the essence of what Nissan orinally intended and it actually works, reliably. Not sure of the real esidual benefit of retaining the meshless sleeve, but I don't get that annoying light, steady or blinking, other than when it is supposed to work. Hope this helps.

Wow, what a post! This has a feel of one of Jeff’s old tech threads that we don’t see these days. Including some pictures of the surgery and procedure for clarity will finish it off nicely. Thanks for taking the time to share your experiences.

 

The historical fix for this from my knowledge, has generally been to just add more fluid whether it looks low or not. I wonder how many owners have had the fault continuously and repetitively like yourself? I would imagine, most of them had given up and locked it out by this point! If it’s not common, it does leave me wondering if there’s potentially an underlying issue causing the excessive heat or fluid turbulence in your case that is above the “usual” owners niggles.

Is your HICAS hydraulic or electric ? Electric from 94 onwards.

 

I used to get that if the battery was low. Sorted by replacing with 370Z battery from Halfrauds