On an air brake system what do you do when the low psi warning light comes on?

if low PSI warning comes on, you need to get vehicle off the road. low PSI means u have low air, or an air leak. this also means you are going to run out of air that operates the brakes

when this happens, the brakes lock on and you ain't going anywhere

warning will come on with enough time to get vehicle to side of road

if you drive a 379 pete and the warning is on and your psi is normal. check the low air switches they are behind the pannel in front of the clutch and brake pedal they are usually corroded

Answer

It depends on WHEN the low PSI warning light came on.

If I was driving and the light came on, that means one of two things: I've got a massive leak somewhere in the air system and it just happened, or the belt to the air compressor broke AND I've got a leak in the system. In either case, pull over before your spring brakes activate. Those will stop you, but they won't turn the brake lights on so there's a chance you'll get rear-ended. Once you're stopped, shut down, get out and listen for the hissing sound. (Most people who get this light while driving ran over a recap, so try to dodge those, okay?)

If it came on while I'm backing into a really complex hole that needs a lot of braking, that's normal. I'd just put the truck in neutral and rev it up a little to build some pressure in the brake system.