One item in air ride trailers that causes a lot of issues during the winter is the levelling valve. This valve keeps the trailer height at the proper level by adjusting the air pressure in the suspension. As the trailer is loaded, it increases the air in the suspension. As the trailer in unloaded, it exhausts the air to return the trailer to the proper height. The issue occurs when there is too much moisture in the air, and it freezes in the levelling valve. Fortunately, this problem is easy to diagnose, and easy to fix, but you will get dirty.
The first sign of a frozen levelling valve is that when you apply air to the trailer, you can hear the air moving through the dash valve, and the air pressure isn’t building very fast. To verify it’s the levelling valve, walk to the trailer, and listen between the axles. If you hear air hissing, then it’s likely the levelling valve.
There are 3 ways to try and sort out a misbehaving levelling valve.
Exhaust and resupply air to the trailer a few times. Sometimes forcing warm air from the truck is all it takes to thaw out the valve. If that doesn’t work, add some methyl hydrate to the supply line of the trailer, and repeat the exhaust and resupply a few times to force the methyl hydrate through to the frozen valve. If that doesn’t work, grab your hammer and crawl under the trailer and check the valve. It’s located between the axles, and will have airlines running to each of the air bags. On the bottom of the valve is the exhaust port, and it has a rubber seal about the size of a nickel. That’s most likely where the air is escaping from. Tap the valve a few times with a hammer. Don’t beat on it like you’re trying to crack a coconut, just a few taps should be enough. Try not to be directly under the valve, or you may get a shower of methyl hydrate. If the sound of leaking air subsides, you’ve solved the problem. If not, the valve needs to be looked at by a certified mechanic.
