What does this sound mean during a light test on a Freightliner?
Posted by theKleShay@reddit | Truckers | View on Reddit | 6 comments
When connected to some certain trailers and while doing light tests, this clicking sound will sometimes happen when the brake lights are flashing. Anyone smarter than me know what it is?
Alubsey@reddit
That’s normal for freightliners
IntergalacticJihad@reddit
Sometimes the ABS unit has an auxiliary power input from the brake lights, if you haven’t connected the ABS power cable but give it power via the brake lights it’ll fire up and subsequently die again when you stop braking.
Ornery_Ads@reddit
ABS is working... if its activating every time the brake lights come on, there's something wrong.
Watch if the ABS light on the driver side rear of the trailer lights up with the brake lights. If so, most likely your ABS fuse (center pin on the electrical pigtail) is blown. That would be a defect on your truck, not the trailer.
Go check fuses.
theKleShay@reddit (OP)
In that case, what does it mean if different trailers are doing it with the same truck? For example I'm currently taking my truck around the yard checking the lights on all the trailers, and only some of them are making the sound. And ABS light isn't coming on either.
hotdog11inch@reddit
Checking the abs
PositionBubbly6087@reddit
That sound is usually the trailer's ABS modulator valves cycling as part of the tractor's automated light/pre-trip test; it’s basically the system checking that the solenoids are firing correctly.