General AHC Questions

[884runner]

I haven’t had a lot of luck finding clear answers to things like:
Why does the AHC have to be turned off when raising the truck on a lift, does that turn on some kind of check valve to keep the fluid from moving even when the engine is off or is that rule apply only when the engine is running? I’m always worried if I take it to get an alignment they will mess something up if they don’t turn it off.
If replacing front struts, do you have to prefill the strut with fluid before installing? Then connect the line and bleed like normal?
I’ve searched but haven’t been able to find clear answers to these. I’m about to replace front struts and trying to make sure I understand some of these basics.

 

[sdnative]

did you look in this thread? Not sure if the answers are there but it's a good place to start.

L

Thread 'LX570 AHC “Basics” - Added as sticky thread for AHC Issues'

Apr 14, 2018

Point of this thread is to serve as a repository for 200-series AHC info, including LX570 and LC equipped with AHC (in select global markets).

Let’s begin with a theory. The 200-series LC (without AHC) and the LX570 (or LC with AHC) are like New York & LA. LC “purists” are like New Yorkers, going on and on about the virtues of “tried and true” spring setups, but in order to enjoy their springs, they seem to have a need to talk some smack about LA/LX with its “over-the-top” hydraulic suspension, “unnecessarily complex” design, and high “cost of repair.” New Yorkers, in other words, make...

• longranger
• Replies: 952
• Forum: 200-Series Cruisers

• 

 

[TeCKis300]

I haven’t had a lot of luck finding clear answers to things like:
Why does the AHC have to be turned off when raising the truck on a lift, does that turn on some kind of check valve to keep the fluid from moving even when the engine is off or is that rule apply only when the engine is running? I’m always worried if I take it to get an alignment they will mess something up if they don’t turn it off.
If replacing front struts, do you have to prefill the strut with fluid before installing? Then connect the line and bleed like normal?
I’ve searched but haven’t been able to find clear answers to these. I’m about to replace front struts and trying to make sure I understand some of these basics.

It's more a safety issue than anything, to keep the suspension from inadvertently actuation causing something unpredictable. The is the same goes with any heavy machinery, which should be put in a static locked out state before working on things.

When lifting by the frame, the height sensors will detect the suspension drooping. As the system has no idea it's being lifted by an external force, it will assume to compensate by reducing AHC pressures to bring ride height back down. Generally innocuous, but safety can't consider every possible scenario so hte manual recommends to switch the system off when servicing.

 

[884runner]

did you look in this thread? Not sure if the answers are there but it's a good place to start.

L

Thread 'LX570 AHC “Basics” - Added as sticky thread for AHC Issues'

Apr 14, 2018

Point of this thread is to serve as a repository for 200-series AHC info, including LX570 and LC equipped with AHC (in select global markets).

Let’s begin with a theory. The 200-series LC (without AHC) and the LX570 (or LC with AHC) are like New York & LA. LC “purists” are like New Yorkers, going on and on about the virtues of “tried and true” spring setups, but in order to enjoy their springs, they seem to have a need to talk some smack about LA/LX with its “over-the-top” hydraulic suspension, “unnecessarily complex” design, and high “cost of repair.” New Yorkers, in other words, make...

• longranger
• Replies: 952
• Forum: 200-Series Cruisers

• 

Yes I’ve looked through this some but at 47 pages it’s hard to find specific answers.

 

[884runner]

It's more a safety issue than anything, to keep the suspension from inadvertently actuation causing something unpredictable. The is the same goes with any heavy machinery, which should be put in a static locked out state before working on things.

When lifting by the frame, the height sensors will detect the suspension drooping. As the system has no idea it's being lifted by an external force, it will assume to compensate by reducing AHC pressures to bring ride height back down. Generally innocuous, but safety can't consider every possible scenario so hte manual recommends to switch the system off when servicing.

Thanks for the info! That makes more sense. So it won’t actually damage the pump or gloves to lift it if someone forgets to turn it off? If the engine and key are off, is there anyway the sensors could try to compensate?
Have you ever replaced struts? I’m assuming bleeding will be the same as changing fluid but I’m not sure how any air that’s trapped in the strut could get to the bleeder below it.

 

[Hopefully]

I am paying 400.00 to have my AHC system flushed. I am even supplying the can of OEM fluid. Seems kind of high but what can I do?

 

[doru]

If the truck is off AHC will not actively adjust the suspension. But if not and on the lift or not, someone may get injured if they have any appendices in the wrong place.

 

[gray rider]

I am paying 400.00 to have my AHC system flushed. I am even supplying the can of OEM fluid. Seems kind of high but what can I do?

DIY? Sorry.

 

[884runner]

I am paying 400.00 to have my AHC system flushed. I am even supplying the can of OEM fluid. Seems kind of high but what can I do?

I flushed my system recently. I did find a few good posts on mud about how to do that. I used two cans of fluid. It wasn’t very hard to do so you may want to look into doing it yourself.

 

[marcfj60]

Yes I’ve looked through this some but at 47 pages it’s hard to find specific answers.

Right? It's almost as much commitment as a Charles Dickens novel.

 

[avrguser]

What is the best procedure to turn the AHC off in cases when you have to be under the vehicle? I know there is the button, and also you can unplug the connector behind the panel near the rear left seat, but is it enough? I always have fear because of this suspension, but I do want to do maintenance on my vehicle as well.

 

[Zill]

What is the best procedure to turn the AHC off in cases when you have to be under the vehicle? I know there is the button, and also you can unplug the connector behind the panel near the rear left seat, but is it enough? I always have fear because of this suspension, but I do want to do maintenance on my vehicle as well.

Just put it in high mode and throw some 6 ton jack stands under the frame on all 4 corners in front/behind the wheels.

If it drops, then the jack stands are there just in case.

 

[avrguser]

Just put it in high mode and throw some 6 ton jack stands under the frame on all 4 corners in front/behind the wheels.

If it drops, then the jack stands are there just in case.

I have a regular 3 ton jack stands from the HF. In your opinion is it a good idea to lift the front and the rear? I usually do either side.

 

[Zill]

I have a regular 3 ton jack stands from the HF. In your opinion is it a good idea to lift the front and the rear? I usually do either side.

You shouldn’t need a lift if you put the AHC in high mode. You can slide the jacks right under the frame and butt them up to the frame in high mode.

I would recommend getting 6 ton jack stands since those 3 tons are per pair (not individually). So a vehicle weighing over 6,000 lbs is not rated for them.

If you’re needing to do wheel rotation, then you can lift from the recommended jack points, but it sounded like you were just wanting to do fluid changes under the rig.

 

[avrguser]

You shouldn’t need a lift if you put the AHC in high mode. You can slide the jacks right under the frame and butt them up to the frame in high mode.

I would recommend getting 6 ton jack stands since those 3 tons are per pair (not individually). So a vehicle weighing over 6,000 lbs is not rated for them.

If you’re needing to do wheel rotation, then you can lift from the recommended jack points, but it sounded like you were just wanting to do fluid changes under the rig.

I get it, so to have the jack stands under the vehicle as a plan B, but don't actually life the vehicle, just the suspension. In most cases yes, fluid changes, but I have a weird noise that I'm trying to figure out, just waiting for warm weather so I can take a look (although I feel like that will be very hard to find and fix).