15 Oct What to Do if Your Truck Won’t Build Air

Often when your truck won’t build air it has something to do with the outside temperatures, like 32 degrees and below. There are a few different components that can cause your truck not to build air. First, get out and determine if you have an external leak either under the cab, under the hood, or on the chassis.

The most common problem that happens is the purge valve gets stuck open on the air dryer and you will only be able to build between 30 and 60 psi, when this happens it’s time to get the dryer serviced. To get going and get you off the road, you will have to shut the truck off and drain the air system.

Then remove the inlet and outlet hoses and fittings from the air dryer and couple them with a half-inch pipe coupler or a half-inch double flare fitting. Once the dryer is bypassed you may treat the system with air guard or air brake antifreeze by pouring some in a tank or at the compressor discharge hose.

Don’t put air guard in a truck system when the air dryer is still hooked up, it will ruin the desiccant cartridge in the dryer. And use a small amount, and get the dryer serviced right away.

If your leak is under the hood it can come from a few different areas like the compressor head gasket, pop-off valve, or air governor exhaust. If you are getting air from the pop-off or head gasket you have a restriction from the compressor to the dryer or air tank.

If you have a dryer, bypass it like explained above and treat the system with air guard. If you don’t have a dryer treat the system with air guard, and if the head gasket was leaking get it to a shop right away.

If the air governor is leaking, replace the governor note the port that’s labeled “exh” must not be plugged when installing the new governor. If you don’t have a dryer the small line goes to “res” and if you have a dryer and are unsure where your lines were, start the truck and the line with air coming out of it goes to “res” and the deadline goes to “unl”.

Only the unused unl and res ports may be plugged, exh port must be open! Some of the mini governors don’t have an exhaust port so there isn’t a chance of it being plugged. If the exhaust is plugged on the governor your problems will get worse, you may blow the head gasket on the compressor.

If the temps are above freezing and your truck builds air slowly it could be a restriction at the air dryer, the discharge line from the compressor, or the compressor itself.