AHC - Rear is stuck on Low, but dashboard shows steady green for L,N,H ? (1 Viewer)

[vhaz]

Gents,
My LC100 from 2000 with approx 170.000 km is now sitting permanently on LOW in the rear.
The high adjustments works fine for the front, can go from from L,N,H with no probs. Just that the rear keeps sitting on low. What I don't get, is that the dashboard indicator stops blinking after front is settled, as if everything was fine. I would have expected the indicator to keep on flashing until also the rear reaches N or H ?

I have read a lot on this topic, but cannot find any info on the logic for dashboard indicator in this case, how it can be indicating a false positive when the rear is not on the desired height.

I hope my problem is only with the rear sensor. To understand the above is part of my suspension troubleshooting.

On a side note: The oil level delta is approx 4 gradients from Low to High, given that it is only the front that has risen makes me hopeful that the rear would count for some additional 4-5 gradients, and my spheres might be OK.

It would be great to tap into some of the extensive knowledge in this forum.

Thanks.

 

[PADDO]

The logic behind the dash display not reflecting actual vehicle height is the system is only as good as the feedback from the sensors. In the rear sensor’s case if it’s failed internally and the physical angular displacement of the potentiometer does not align electrically then the system gets a false N height. Or if the bracket has slipped/corroded then the system can think it’s at N height (ie potentiometer in its mid sweep between 0-3900 ohms approx and returning a nulled 0 error voltage) whilst the vehicle isn’t physically at the height you want.
In a normally functioning system with no faults or problems you can set N height up anywhere, within reason, within the normal range of travel ie sensor lift or sensor slam if you’d like. Inject a faulty sensor where the electrical output doesn’t correlate with angular displacement or a broken mounting bracket and you can get strange things happening.
I’ve got a busted sensor on my shelf where the potentiometer stub to internal resistive wiper isn’t permanently aligned (I broke it rushing a changeover) and I can get that to give crazy feedback results.
The simple check is to measure vehicle physical height to sensor feedback. At a stock N height of 19.5ish and 20.5 sensors should feedback 0/- 0.2 at L they should feedback about -1.7 or so and H should be +1.8 (inches, you can do the metric conversion). Importantly you must get consistent results, as an inconsistent feedback signal will give you inconsistent actual heights. Then in some circumstances a failed sensor might throw a code and shut the whole system down, but initial random and inconsistent height behavior is the norm for most failing sensors.

 

[vhaz]

Thanks for an extensive answer. Spent a few hours with this today. The bracket is teared by rust so it can flex a bit (can be somewhat moved by hand), i.e. not firmly fixed to the body. Each time I "knocked on" the sensor, it would be able to raise to high. Never to normal, and always only once - I needed to knock on it again before it could raise. I hope this does not imply a ECU problem.

I am confused about what size of the wrench to use for removing the bolts holding the bracket. It seems to be inbetween 11 and 12 mm. This should not be imperial/inch spec bolts, right? Anyone who knows?