AHC dips and rises on startup and at lights occasionally is it normal?

[SirLR]

I recently had my 06 lx470 with a super harsh ride and it used to adjust every time i started the truck and ocassionally at stop lights and now I just had my globes replaced and it does not do any adjustments anymore. My ride is great now but I don't know if the adjustments were normal. Could anyone chime in.

 

[Snow Wagon]

Hello SirLR,
Do you have TechStream or another way to read the AHC pressures?
If not get something that will read them.
1st thing you need to know is what your AHC pressures are.
Did you have a shop that understands AHC replace your globes?
What else did they do?
Did they adjust your Front Torsion bars?
Did they replace your Rear Coil Springs or add Spacers to get your Rear AHC pressure to spec?
Did they replace your AHC fluid?

If everything is in spec / working correctly, the system just makes minor adjustments to keep your height correct.

Does changing from N to L and / or N to H work correctly?

Enjoy.
Tom

 

[SirLR]

Hello SirLR,
Do you have TechStream or another way to read the AHC pressures?
If not get something that will read them.
1st thing you need to know is what your AHC pressures are.
Did you have a shop that understands AHC replace your globes?
What else did they do?
Did they adjust your Front Torsion bars?
Did they replace your Rear Coil Springs or add Spacers to get your Rear AHC pressure to spec?
Did they replace your AHC fluid?

If everything is in spec / working correctly, the system just makes minor adjustments to keep your height correct.

Does changing from N to L and / or N to H work correctly?

Enjoy.
Tom

I do have techstream and was going to go ahead and check. This shop usually works on kdss but they also work on ahc occasionally. They just changed the globes and flushed the system. They did not adjust or cross level any of the suspension which I will let them know about today since that was part of it. Height changing works perfectly.

 

[Snow Wagon]

Here's the procedures to follow...

AHC Height Check

Check Height at Normal Height at All 4 Corners (Level Ground, SUV Running, Full Tank of Gas):
- Front should be 19.75” Hub Center to Fender
- Rear should be 20.5” Hub Center to Fender

Adjust Torsion Bars to get the Front Cross Level
- 1 Complete (360 Degree) Turn on 1 Torsion Bar Bolt will raise / lower that corner ~1/8”
- The goal is less than 1/4” Difference

After the Front is Cross Level...

AHC Pressure Test

SUV with a Full Tank of Gas.
SUV on Level Ground.
Disconnect Fluid Temperature Sensor (Optional…)
- On the side of the pump assembly, rear connector with 2 wires
- Center connector with 3 wires is the pressure sensor
- Forward connector with 2 heavier blue and white wires is for the pump motor

***Change Vehicle Height to L.
Wait 60 Seconds.
Change Vehicle Height from L to N.
Wait 30 Seconds after N is reached.
Read Front Pressure.
Front Pressure should be 6.9 MPa.

If Front Pressure is Higher than 6.9 MPa, adjust Torsion Bars.
1 Complete (360 Degree) Turn of Both Torsion Bar Bolts will lower the Pressure by 0.2 MPa

After Adjusting Torsion Bars, Repeat Step ***.
If Front Pressure is now 6.9 MPa, the Front is Correct.

Read Rear Pressure.
Rear Pressure should be between 5.6 & 6.7 MPa

If Rear is not in Spec, purchase new rear AHC springs or coil spacers (30mm or similar).
Note: 30mm Spacers only decrease your rear pressure by around 0.5 MPa.

You only need to Install Higher Rate Rear Coil Springs (like King Springs...) if you're always carrying extra weight (like an Aftermarket Steel Rear Bumper w/ a Spare Tire Carrier).

Installing New Rear Coil Springs and / or Spring Spacers will not change the Rear Height of your SUV.
It will only change the Pressure in the Rear of the AHC system.

The AHC System supports part of the weight of your SUV (via Hydraulic Pressure), while the Front Torsion Bars and Rear Coil Springs support the rest of the weight of your SUV.
The more weight the Torsion Bars and Coil Springs support, the less weight the AHC has to support.
There is a happy medium as to how much weight each supports.

IMO, you should also perform a Graduation Test (to make sure your new Globes are healthy), and perform a Pump Test (to make sure your Pump is healthy).

Good luck.
Tom