Air Suspension Troubleshooting

This page provides some tips and pointers for common issues we see with air suspension systems.  

While this list is fairly comprehensive, it may not cover everything and should be used as general guidance rather than a complete diagnostic process.  If in doubt, feel free to get in touch and we'll do our best to help.

• My vehicle won't lift
• My vehicle drops overnight
• Help, I have a leak!
• My controller isn't turning on
• My compressor isn't running
• My compressor runs constantly
• My compressor is noisy
• My fuses keep blowing
• My presets are inaccurate
• My tank is full of water
• My controller is showing "pressure sensor failure"
• I have a knocking noise

My vehicle won't lift

Does the management system turn on/work?  If not, see "My controller isn't turning on". If it's on, start by checking the tank pressure. 

If the tank is empty or low and the compressor isn't running, see "My compressor isn't running". 

If the tank has pressure and everything else is showing normal, check that the management system is operating the valves correctly and that there are no restrictions in the air lines.

If only one corner refuses to lift, concentrate on that corner's air spring and fittings.  It can often help diagnostically to switch the air lines at the management side, to see if the fault stays with the corner, or stays with the management.  If the management is at fault but you need to move the vehicle, try and source a tee connector, as this will enable you to join two air lines into one working valve.  It will connect the bags together so won't be nice to drive and you can't use presets, but it will allow you to raise the vehicle.

My vehicle drops overnight

Some pressure loss over time is normal, particularly as temperatures change, it isn't uncommon to see a drop of 10psi or so overnight.  However, if it's a significant drop or the vehicle is sat on the floor, it's likely to have an air leak.

Help, I have a leak!

Can you hear it?  If so, that makes troubleshooting easier, you can follow the noise and figure out roughly where it's coming from.  If you can't hear it, you will need some "leak detection fluid"- a thick mix of washing up liquid in water is fine.  Put it in a spray bottle, use a paint brush to apply it to all the fittings, air lines, air bags (particularly where the bags join to the struts), manifold connections (taking care not to get any electronic parts wet), pretty much everything within the system.  Now look for anything that's bubbling up. 

Nothing obvious? Give it time, slow leaks can take a while to start foaming.

More often that not, it'll just be a simple fitting or an O ring that needs replacing, so check these areas first.

Tank leaks can be tricky.  If you have an unexplained tank leak that you can't diagnose, it may be worth investigating the check valve.  This is a non return valve that sits between the compressor and the tank.  Also see "My fuses keep blowing".

My controller isn't turning on

Depending on the system, there are usually two fuses involved, and they're often on inline fuse holders.  A larger fuse (usually around 30A) at the battery which feeds a constant live, and a smaller fuse (usually 3-5A) that feeds a switched live from an ignition source. If either fuse is blown, chances are the system won't power up.

The ignition source fuse is usually located near a fuse box within the car or engine bay, and most of the time these are piggybacked off an existing fuse.  If the fuse is intact, check the connection, as these can sometimes work loose with vibrations over time.  If this fuse is blown, it is most likely a snagged wire or a short to ground somewhere along the wire.

The constant live fuse should be close to the battery.  Again if the fuse is intact, check the connection.  If this fuse is blown, it could be either a wiring fault like a snagged wire or short circuit, or a compressor issue.

If the fuses are OK:

- Check the connection to the display.  These often have small connectors on the back of the display, and another about a metre further along the wire.

- Check the connection to the manifold. Occasionally, though rare, it may be necessary to reboot the manifold, by unplugging the main connector, leaving it for a couple of minutes, and plugging it back in.

Failing that, if you have an Air Lift system, the Air Lift user guide has a very helpful diagnostics section which can help to highlight what the fault may be.

My compressor isn't running

Firstly, check the main fuse at the battery.  If you have a volt meter, check to see if the compressor is getting 12v and that you have a good ground.

If the fuse is blown, see "My fuses keep blowing".

There is usually a switching relay that controls the compressor.  These can wear out and need to be replaced.  You can test them with a multimeter, or they are cheap enough and readily available to just try a new one.

My compressor runs constantly

There could be a few reasons for this, check the tank pressure to start with (if you have a tank gauge/display).

Tank filling normally, or overfilling: Something is preventing the compressor from switching off.  This could be caused by a sticky relay, a faulty pressure switch (common in older or manual systems), or an internal issue with the management.

Tank not filling, or filling slowly: Firstly, check the inlet filter to see if this is clean.  It could also be a blockage in the line, or potentially a faulty check valve.  However if those are OK then invariably, this is a sign that the compressor is worn out.  The piston seals or barrels wear over time, and unfortunately it may be best to replace it.

My compressor is noisy

All compressors do make noise, but sometimes they're louder than they need to be.

The amount of noise quite often comes down to the way it's mounted.  Compressors generally have rubber mountings, these can wear out over time, or can be installed incorrectly.  It's important to fit them with the correct washers.  It helps to put sound deadening material on the panel the compressor is mounted to.  Don't be tempted to box in the compressor too tightly, as they need air flow to function, and for cooling.

Dedicated compressor isolator kits are available and work well.

If it is mounted correctly, check that nothing else is vibrating against it or on the panel, it's common for exhaust heat shields to rattle if they're nearby!

Sometimes, though rarely, a compressor can get noisy due to a blockage, or a worn piston or imbalanced motor.

My fuses keep blowing

Firstly this cannot be stressed enough... Do NOT, ever, under any circumstances, fit a higher rated fuse. That's when things get burny.

Check the wiring is OK, no snagged wires, shorts to ground.  You also need a good, solid ground connection for the compressor.

Compressors tend to blow fuses if they become blocked or overheated. Check the compressor's inlet filter to make sure it's clean and isn't restricting air flow. 

More often than not, this is a sign of an over tightened or faulty/clogged check valve.  This is a non-return or one-way valve fitted between the compressor and tank, which allows air to enter into the tank but stops it from feeding back into the compressor.  If these fail, the compressor gets overworked or stalls, often overloading the fuse in the process.

Another symptom of check valve failure is if you have a slow tank leak that you've been unable to figure out.  You can often test this carefully by seeing if any air flows back through the inlet port on the compressor.

It may just be over tightened so that's the first thing to try.  They can sometimes be removed and cleaned, or replaced. Replacing the check valve simply a case of draining the tank and swapping it out for a new or uprated one - note that there are a couple of different sizes available.

My presets are inaccurate

Try activating the preset again to see if it works a second time, as sometimes it will fail if the tank pressure is too low.  Failing that, try recalibrating the system.  You can also try toggling "axle equalisation" on or off as this sometimes creates inaccuracies. 

In some cases presets are inaccurate due to the amount of pressure and/or air volume required in the air bags.  Some bags need to be run at very high pressures, so it's important to make sure that your tank pressure is adequate for the air bags you are running.  Likewise, if you have large air bags, a small tank can often struggle to fill these in one motion.

If it still persists, it may be that the air lines are larger than ideal for the weight of the vehicle.  Larger 3/8" air lines are generally quite fast on lightweight hatchbacks, and can over/undershoot on presets.  The good news is that there are simple ways to slow them down, such as by installing a length of narrower diameter air line somewhere along the route.

If the pressures are accurate but vehicle height isn't always the same, this is a different story entirely, and you may find that the addition of height sensors would be beneficial.

My tank is full of water

This is normal, but the tank needs draining.  Air from the atmosphere is surprisingly wet. As air is compressed, the humidity is condensed into water.  This water can get into the valves and air lines, which can cause problems, so it's important to drain the tank periodically.  We generally suggest once a month to start with, though every car is different.

It's worth having a water trap installed between the tank and the management system too, and emptying it regularly, as this will catch the majority of excess water before it reaches the important stuff.

My controller is showing "pressure sensor failure"

If it's freezing cold, it may be that there's water in the system (see "My tank is full of water").  Allow the manifold to thaw out, and make sure that the tank air is dry.

Failing that, unfortunately this could be an internal problem, and it's best to contact us, your supplier, or the manufacturer for more help.

I have a knocking noise

Knocks should always be checked out as a matter of urgency.  It could be absolutely anything, bushes, balljoints, shocks, you name it.  Air suspension does tend to put a bit more stress on these components due to the wide range of height adjustment. That said, there are few common causes:

If the system is new, check all of the fasteners.  Just because they were tight at the time, once the parts bed in, you might find the bolts need another quarter of a turn.

Rebound knock - This is the most common particularly on performance air setups.  It's a deep "thud" when coming off of speed bumps.  This is usually due to having too much pressure in the bags, and the shock travel is at its upper limit.  It's relatively benign and not a sign of a problem, but you should take care to avoid this happening too often, so it's worth adjusting the suspension to suit.  It can usually be reduced by lowering the pressure or stiffening the damping.

Top mount bearings - usually these are thrust bearings or spherical bearings with PTFE (or similar) linings, these can wear out over time and cause a creak when steering and/or a knock when driving over rough ground.  They're relatively low cost and straightforward to replace, but they should be replaced as a matter of urgency as they can lead to other issues such as movement between the air spring and strut assembly, trapping air lines, or alignment issues.

Drop links - These can wear over time, or they can foul on other components at extreme height.