High as a kite, hard as a rock! (Yes AHC again...)

Joined
Sep 13, 2007
Messages
746
Location
Denmark
 
 
Hi guys!

I have a 2001 VX100 1HD-FT diesel with 300,000 miles on it.
I've owned it for two years and love the comforts over the HJ61 it replaced.

But the AHC is acting up!

I don't want to go conventional, I want to keep the AHC.

AFAIK everything except height sensors are original, and I know the globes must be shot, but before replacing them, I'd like your input.

The truck has been getting higher and higher and harder and harder.
And the height control button does absolutely nothing besides making the green light go up or down a few seconds, no change in ride height. It used to work, but intermittently.
upload_2019-1-19_21-45-18.png


I have Techstream and hooked it up and ran a fault diagnostic, no codes...
So I went to AHC live got this screen shot:
upload_2019-1-19_20-35-33.png

Height FR: 73.8mm (~2 9/10")
Height FL: -72.8mm (~-2 7/8")
Height RR: -7,7mm (~-3/10")
Notice the difference in value on the front axle, that's 146.6mm or 5 3/4"! Shoudn't it be about the same?
No pressure readings....

So I used the active test and levelling solenoids to lower the car:
upload_2019-1-19_20-45-27.png

Height FR: -66.6mm (~-2 5/8")
Height FL: -102.8mm (~-4")
Height RR: -54.8mm (~-2 1/8")

Difference FR: 140.4mm (~5 1/2")
Difference FL: 30mm (~1 3/16")
Difference RR: 47,1mm (~1 7/8")
Notice the difference, everything carried out on a perfectly level shop floor, and I don't believe there was a difference of 4" between front left and right...

Notice again no pressure readings..
All realyas etc. checked in active test and I heard them click.

Then I turned the ignition off, and on again, and the truck came up a bit:
upload_2019-1-19_20-57-7.png

Height FR: -1.6mm (~0")
Height FL: -93.6mm (~-3 5/8")
Height RR: -45.2mm (~-1 3/4")

So something seems odd, I redid the tests and checked height from floor to the fender lip:
upload_2019-1-19_21-37-51.png

(Sorry for not doing in ", but 50mm ~2")
FR seems to be almost the same between techstream and a fender lip measurement, the rear is off by ~10%, but RL is WAY off and doesn't change with the car, so that must be bad...

I got pressure readings this time: front: 8.0 Mpa-g and rear is 7.3Mpa-g, so bad too!

How would you guys approach this?
 
Joined
Sep 27, 2007
Messages
1,760
Location
Charlotte NC or ACT area Australia
 
 
Suspect your FL height sensor/linkage is defective so that’s worth inspecting. To set up height: On flat level ground set the actual front and rear vehicle heights to where you want them in active test. For stock N front height you’d set 500mm hub center to fender bottom and 520mm for the rear. We don’t use ground to fender because it’s easier not to work around tire sizes and inflation. Now this 500/520mm is your N height and both front sensors should be 0.0 +- 5mm and the rear 0.0 +- 5mm. With the engine off but ignition on you’ll get height sensor feedback in Techstream without the danger of the vehicle self leveling on you, adjust your height sensors accordingly to read as close to zero as possible at the height you’ve chosen to be your N. You can do this with the front wheels off (one at a time) too, support the vehicle and use a second jack to raise the LCA to get your 500mm axle center to fender and adjust the sensor as it’s all right in front of you with nice easy access. I have a usb extension and do this with Techstream laptop right beside me at the wheel well. This is done with engine off, ignition on.
Some checks you can perform on the sensor potentiometer: Between pins 1 & 3 you should measure around ~3700 (iirc or could be ~3600 ) ohms, and at mid point of the stub shaft rotation (the wiper will swipe through about 175 degrees) you should read half the total resistance between pins 1&2 and 2&3. If you’re not getting a clean change in R values as you gently rotate the stub shaft/wiper then you’d look at a clean/inspect or replace.
You’ll need to have your height and self leveling system working properly to get valid pressure reading when raising from L to N. With that extra height your front pressures go up about 2.2MPa per 25mm and that in itself will make the dampening rock hard, not to mention the system may well have safed out the variable damping and set it to 16, the hardest. You won’t get pressure reading in active test either because it’s a test mode.
 
Joined
Sep 13, 2007
Messages
746
Location
Denmark
 
 
Thanks Paddo!

I checked the LH sensor, and got 50 +-2 from end point to end point with it removed. I took it apart and found corrosion and grime, so I cleaned well, lubricated and put it back together. Then I got a reading from -122 to -114. Needles to say, its dead!
I got hold of a used one I’ll try tonight.
If it works, I’ll try your method, it seems easier than the FSM...Do I have to do something to get it out of failsafe?
 
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