Definitive list of AHC maintenance items (6 Viewers)

[Actualeyes]

That said, I don't believe it is a good idea to rely on the airbags long term as they are likely to make the ride bouncy, and support the vehicle less as the AHC/Springs lift. My plan is to buy packers ASAP and fit them. I think 20mm should give me at least a couple of years before I need to go the full expense of new springs.

Well welcome to the AHC Reprobates Club - us recalcitrants who just maintain our AHC!

On your airbags, what they are effectively doing is carrying some of the load on the rear that your sagged rear springs no longer can, or perhaps were never intended to if you are carrying extra load. Personally I can't see anything wrong with that - that is what the airbag helpers are supposed to do. If you load the car up more (e.g. put on a heavy tow load) you can just pump them up a bit to level the car before starting (so the AHC doesn't try to do it for you), or if you do it after starting, pump them up until rear neutral pressures are within spec.

I recommend you just buy new rear coil springs rather than packers. They are quite inexpensive - probably not that different to a decent set of packers, basically the same job to install, and you are not adding another potential point of failure.

Cheers,
Andrew.

 

[CappyKD]

Well welcome to the AHC Reprobates Club - us recalcitrants who just maintain our AHC!

On your airbags, what they are effectively doing is carrying some of the load on the rear that your sagged rear springs no longer can, or perhaps were never intended to if you are carrying extra load. Personally I can't see anything wrong with that - that is what the airbag helpers are supposed to do. If you load the car up more (e.g. put on a heavy tow load) you can just pump them up a bit to level the car before starting (so the AHC doesn't try to do it for you), or if you do it after starting, pump them up until rear neutral pressures are within spec.

I recommend you just buy new rear coil springs rather than packers. They are quite inexpensive - probably not that different to a decent set of packers, basically the same job to install, and you are not adding another potential point of failure.

Cheers,
Andrew.

I'm a member of the club too. I have new oem non AHC rear springs sitting in my truck waiting to be installed and am planning on hooking up my mini vci and cranking those bars until I am in spec. If I can't get the front in spec, I will source other torsion bars rather than re-index.

I can't wait to have my AHC back and my stink bug. As soon as I put the new rear ARB bumper on, no more stink bug.. I was already at the edge with a roller drawer roller floor and ARB fridge.

 

[Wilsil]

Is the AHC system still working effectively when changing the springs? You are changing the setup without "telling" the system.
Not sure, just asking.

 

[Actualeyes]

Is the AHC system still working effectively when changing the springs? You are changing the setup without "telling" the system.
Not sure, just asking.

Mine is. No need to tell it anything (anyway the kids think I'm crazy if I talk to my Hundy!).

In short the load is carried by:

1. coil springs in the rear
2. torsion bars in the front
and
3. the AHC system which adjusts the pressure in the dampers until the height sensors read what it expects. Now if the pressure gets too high it just says "the AHC is carrying too much load" and defaults back to "L"

If your coil springs sag they take less load so the AHC takes more.
If your torsion bars sag they take less load so the AHC takes more.
If you add more weight the coil springs and torsion bars only take the same load so the AHC takes that extra load you added.

Increase the spring rate of the coils (e.g. newer or even non AHC coils) or add spacers and the AHC takes less load (e.g. lower pressure mostly in the rear)
Increase the torsion on the torsion bar and the AHC takes less load (mostly at the front).

Adding air bags takes some of the load, so the AHC is taking less (lower pressure in the rear).

When the AHC is within spec pressures front and rear the dampers work well, the ECU controls the Comfort/Sport settings and the response rates of the dampers and everything is rosy. When pressures are too low you are left with springs without any effective damping - e.g. soft and springy. When pressures are too high the dampers don't have the capacity to help so everything gets very harsh. When within spec, everything is "just right" so to speak. This is the normal situation when people get frustrated with the AHC and just delete it... and the basics of AHC are beyond most mechanics shops so they just swear and cuss at the AHC and say that it is an expensive system to maintain. In fact if you're at a toyota or lexus stealer they will try to charge you big money to replace major system components instead of these adjustments.

One last thing for completeness, changing the sensors so that the ECU is tricked into keeping the vehicle higher increases the AHC pressures. You can lower them in the same way as described above - tighten up the torsion bars, increase the spring rates or use packers.

 

[Wilsil]

Got that.

How is the soft/comfort setting linkedto this?In my case, the AHC is working in that sense that it goes up, it goes down when I push the button, eventhough the pressure isn't within spec.
When loading up and towing the CT it sometimes goes to L.
But unloaded, cornering is not funny. The switch soft/sport or whatever is on it, doesn't seems to do anything and the car has a big lean.

 

[Actualeyes]

Got that.

How is the soft/comfort setting linkedto this?In my case, the AHC is working in that sense that it goes up, it goes down when I push the button, eventhough the pressure isn't within spec.
When loading up and towing the CT it sometimes goes to L.
But unloaded, cornering is not funny. The switch soft/sport or whatever is on it, doesn't seems to do anything and the car has a big lean.

Hey Wilsil, I hope you're well.

The lean suggests that one torsion bar is not adjusted high enough to match the other. During normal operation the valving between Left and Right is open so it does not level left and right. Given the number of mechanics and suspension folks with no idea about how AHC works, at some time in the vehicle's history somebody not knowing what they're doing has fiddled with it.

Solution: with the engine off "turn by turn" adjust the low side torsion bar tighter and the high side torsion bar "looser" (sorry not quite right word but you get my drift) until it is level. It will be easiest if you put it in H first. I'm not sure how you tell if it is level to be frank. I suspect there is some camber allowance that means if you measure left and right the same way there should be some difference. Perhaps some other Aussie will chime in. In the meanwhile use your eye! Then hopefully when you start the car and adjust it H to L to N (say) it should stay level. It might take a couple of attempts. Some people say to take the load off the wheels when adjusting it. I never have, and it has not been a problem.

The issue loading up with the CT is simply overloading the AHC and rear coil springs and/or helper air bags will help that.

Hopefully once the lean is fixed the cornering issue you refer to will be fixed.

If not, (well whatever) you should check for DTC does to make sure AHC valves are not throwing codes.

The comfort/sport setting just changes the valving response time of the dampers as I recall (but this is of no effect if the dampers are on a very high pressure. The ride will always be harsh. Once you get the pressures in spec you'll be surprised how smooth the ride is and perhaps notice the difference between Comfort (read Lincoln Town Car) and Sport (not quite Porsche 911 but you get the idea).

HTH,
Andrew.

 

[hkeller]

OK. Been trying to get Tech Stream to work on a couple of different computers with no success. Can someone tell me what specs a computer needs to run Tech Stream? Thanks,

 

[CappyKD]

OK. Been trying to get Tech Stream to work on a couple of different computers with no success. Can someone tell me what specs a computer needs to run Tech Stream? Thanks,

Windows xp. Did you install the mini vci driver that is included on the cd?

 

[hkeller]

When I put the disk in my Windows 7 machine, the computer started formatting it. Now, I am trying to load the tech stream software that uHu was kind enough to send to me. Does the machine need to be 16, 32 or 64 bit? Thanks,

 

[CappyKD]

When I put the disk in my Windows 7 machine, the computer started formatting it. Now, I am trying to load the tech stream software that uHu was kind enough to send to me. Does the machine need to be 16, 32 or 64 bit? Thanks,

Windows XP 32 bit.

 

[hkeller]

Thanks!

 

[CappyKD]

Thanks!

Did you get it working?

 

[uHu]

...But unloaded, cornering is not funny. The switch soft/sport or whatever is on it, doesn't seems to do anything and the car has a big lean.

The 100 is not a sports car.
What you need to check is that the valves work right. When turning the steering wheel more than 35 deg, the valves between right and left will be closed, thereby reducing the lean. Using the techstream, you can check that the steering angle sensor is straight (that's another area where most mechanics have no idea what they are doing. Whenever adjusting the steering geometry, the ahc steering wheel sensor has to be checked as well).

 

[hkeller]

Sorry I didn't respond sooner, I was out of town this weekend. OK I got the software to run, but I cannot get it to recognize the USB cable. I think I need a different USB driver for the cable. Any thoughts. Man, I thought I had it . . . then wouldn't connect. Shoot.

 

[Actualeyes]

Sorry I didn't respond sooner, I was out of town this weekend. OK I got the software to run, but I cannot get it to recognize the USB cable. I think I need a different USB driver for the cable. Any thoughts. Man, I thought I had it . . . then wouldn't connect. Shoot.

I think if it tries to connect it is recognising the cable.

 

[CappyKD]

I put 6 turns on each of my Torsion bars this morning and one day this week I will put in or have put in, the new non - ahc springs and gaskets I got from Cruiser Dan. Then I will break out the mini vci and do a final TB adjust ( with 2 G 31 batteries, a puma air compressor and tank, roof rack, a 12k winch with steel rope and a Ironman combo bar, I expect to need more like 8-9 turns.) to get back on the low end of the spec then do a droop check, steering center reset and get an alignment. I should be back in good shape as far as my suspension goes. I can already feel the difference in the front with 6 turns and see it at the wheel well.

 

[Actualeyes]

Sorry I didn't respond sooner, I was out of town this weekend. OK I got the software to run, but I cannot get it to recognize the USB cable. I think I need a different USB driver for the cable. Any thoughts. Man, I thought I had it . . . then wouldn't connect. Shoot.

It does need Windows XP...

 

[Wilsil]

I had the same think happemning the first time.
After rebooting it worked and the program did recognise it.

 

[tarpaigh]

I am hoping someone can help me here. The drivers side of my vehicle sits lower than the passenger side. I measure about an inch difference at the wheel well between the sides. I thought this would be due to torsion bars. I hooked up tech stream software and found the height control sensor show a difference of 0.7 inches between the right and left with the FR 0.4 while FL is -0.3. The ahc pressure in the front was 8.2, rear was 6.2.

Do I need to crank both torsion bars and change the height control sensor height? I appreciate any help.

 

[PADDO]

I am hoping someone can help me here. The drivers side of my vehicle sits lower than the passenger side. I measure about an inch difference at the wheel well between the sides. I thought this would be due to torsion bars. I hooked up tech stream software and found the height control sensor show a difference of 0.7 inches between the right and left with the FR 0.4 while FL is -0.3. The ahc pressure in the front was 8.2, rear was 6.2.

Do I need to crank both torsion bars and change the height control sensor height? I appreciate any help.

The front height control sensors average their delta from 0 displacement to set overall front height, so I think what you're seeing is the result of uneven torsional force (assuming you're on level ground and not loaded up). You need to get your vehicle cross level first and then front neutral pressure down to, ideally, 6.9MPa. Don't adjust your height sensors ATT. Crank the left TB up say 4 turns, crank the right down same amount (incrementally splitting the difference) go for a drive and remeasure vehicle cross level, re adjust in smaller increments as necessary. When you're cross level to less than 10mm difference fine tune your neutral pressures by cranking both up or both down the same number of turns and front height should fall into place. Hopefully you won't need trim packers for the rear, but they are cheap and easy to install if necessary.