AHC Reset / Adjustments Pricing (1 Viewer)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Feb 3, 2021
Threads
5
Messages
35
Location
Austin, TX
Hey 100 fans,

I recently purchased an '07 LX 470. After proudly parking it in the garage I looked and thought, "huh that looks like it's leaning to the left". A couple of Mud searches later and a whole new world is opened with terms and concepts relating to AHC.

@suprarx7nut YouTube video was really awesome, but I don't have the tools to fix myself.

If I were to take this to an LC specialist or the dealership, what should I expect to pay for getting AHC dialed in?
 
Hey 100 fans,

I recently purchased an '07 LX 470. After proudly parking it in the garage I looked and thought, "huh that looks like it's leaning to the left". A couple of Mud searches later and a whole new world is opened with terms and concepts relating to AHC.

@suprarx7nut YouTube video was really awesome, but I don't have the tools to fix myself.

If I were to take this to an LC specialist or the dealership, what should I expect to pay for getting AHC dialed in?
We charge $100 for a basic AHC overview. Takes us an hour at a leisurely pace. That includes torsion bar adjustments.

It should be less than an hour of labor, but the hard part will be finding a shop that knows what they're doing.
 
A whole lot more than a set of tools.

Most dealers don't have a clue how AHC works. Best to find an indy who knows or learn the system yourself. It's not hard.
 
We charge $100 for a basic AHC overview. Takes us an hour at a leisurely pace. That includes torsion bar adjustments.

It should be less than an hour of labor, but the hard part will be finding a shop that knows what they're doing.
Know any good shops in or around Austin? CO is a little far for me ;)
 
Thanks for the rec! I just emailed Edwin.

(I have little personal experience with LCS, but my brother swears by them, for his GX460, my niece’s GX470, and my nephew’s LC80, none of which have AHC.)
 
Left lean has nothing to do with the AHC. All cruisers do that, ahc or not. The weight is higher on the left, so the springs sag sooner. You adjust the torsion bars to compensate.
The AHC does not adjust for left/right lean. but it is an advantage to know how the ahc system works for any work on the suspension.
 
Left lean has nothing to do with the AHC. All cruisers do that, ahc or not. The weight is higher on the left, so the springs sag sooner. You adjust the torsion bars to compensate.
The AHC does not adjust for left/right lean. but it is an advantage to know how the ahc system works for any work on the suspension.
The lean is present on AHC and not, but without knowing pressures you might be throwing pressures off by blindly raising the left side.

It's probably safe to just turn the driver's torsion bar until it's level and that's what should be done if no AHC mechanic can be found. However, if you can find someone that can load up pressures you can take an additional 15 minutes of labor and turn it into a cross-level and pressure adjust - and we can probably all assume it needs a pressure adjustment.
 
Left lean has nothing to do with the AHC. All cruisers do that, ahc or not. The weight is higher on the left, so the springs sag sooner. You adjust the torsion bars to compensate.
The AHC does not adjust for left/right lean. but it is an advantage to know how the ahc system works for any work on the suspension.
Maybe so. Original measurements were 19 5/8" on the LF and 20 3/4" on RF -- roughly the same for the rear.

That was on N height. AHC wouldn't shift into H height.
 
Maybe so. Original measurements were 19 5/8" on the LF and 20 3/4" on RF -- roughly the same for the rear.

That was on N height. AHC wouldn't shift into H height.
Late to the party ....

@uHu and @suprarx7nut already have summarised the "lean" issue. My previous long explanation on the subject is found here and includes some suggestions on where to look for some of the differences which can arise.

Unless already fixed, your Front hub-to-fender tape-measurements indicate that cross-levelling with torsion bar adjusters is required to equalise weight on Left and Right torsion bars and to equalise Front hub-to-fender distances to eliminate lean. This is the first step in any effort aimed at getting the AHC/TEMS systems to perform properly. Front cross-levelling on level ground with engine "OFF" and with vehicle unloaded and fuel tanks full also should go most of the way to equalising Rear hub-to-fender distances as well -- unless some of the oddities mentioned in the referenced post are present.

Just to jump to a few clarifications in advance ....

Cross-levelling cannot be done with the AHC Height Control Sensor adjusters -- physically and hydraulically impossible because when the vehicle is at rest or steering is straight ahead, AHC Front Left and AHC Front Right are hydraulically connected and are at equal pressures. Ditto AHC Rear Left and AHC Rear Right. However, AHC Front and Rear are not hydraulically connected in a similar way.

On a vehicle with AHC/TEMS suspension, it is the Height Control Sensor adjusters, not the torsion bar adjusters, which are used to set the height of the vehicle. This is very different to a conventional suspension.

It is important to understand the variables involved in this kind of suspension system. The higher the vehicle is raised, the more that springs and torsion bars are extended and relaxed and the less weight they carry. This means that the higher the vehicle is raised, the more weight the AHC system must carry and so the AHC pressures are higher when the vehicle is higher.

So when checking and re-adjusting the AHC system, the general sequence is always the same:

1. Cross-level front using torsion bar adjusters,

2. With cross-levelling already done, set Front and Rear heights using Height Control Sensor adjusters -- most people use the IH8MUD-recommended hub-to-fender approximations of 19.75 inches Front and 20.50 inches Rear, rather than the fiddly height specifications depicted in the Factory Service Manual (FSM),

3. With Front and Rear heights already set, adjust AHC pressures using torsion bar adjusters to transfer weight from AHC system to torsion bars (or vice versa if necessary). Correct AHC pressures are vital for good damping performance and a comfortable ride. (This step does not change the height of the vehicle because that is set by the position the Height Control Sensors and the automatic self-levelling feature of the AHC system),

4. With AHC pressures correctly adjusted, check overall condition of 'globes' by measuring difference in graduations at the AHC tank at " LO" height and "HI" height --- 14 graduations means ' globes' are near new, 7 graduations means that it is time to replace 'globes'.

Inability to raise the vehicle to "HI" height is a very strong indication that AHC pressures are higher than the FSM-specified range.

Techstream or some other scanner which can read the AHC Electronic Control Unit (ECU) is a vital tool. It is essential to be able to read AHC pressures and make the necessary adjustments and also read and interpret the Diagnostic Trouble Codes (DTC's) should any arise. This is an important question to ask any workshop. If their scanning equipment cannot do this, then there is no way that workshop can carry out competent work on the AHC/TEMS systems.

Immense detail and assistance is available on IH8MUD and in the Factory Service Manual. Even if you decide to have others do the work and not handle the tools yourself, it is worthwhile learning how the AHC and TEMS systems work in detail. This makes you a well-informed customer, capable of recognising proficiency or the lack of it when dealing with folks at workshops. Sad to say, even though the +25 years old technology of the LC100/LX470 AHC/TEMS systems is not very complicated as electro-hydraulic systems go, it is hard to find AHC proficiency at automotive workshops, even at many Dealerships. The AHC/AVS systems on LC200, LX570 and the forthcoming LX600 are more complicated than the systems on LC100/LX470. Exploration of the IH8MUD "200 series" Forum may (?) help identify workshops with the necessary equipment and proficiency.
 

Attachments

  • AHC - Cross level per FSM.pdf
    240.1 KB · Views: 50
Last edited:

Users who are viewing this thread

Back
Top Bottom