Shanghai Trailer has accumulated a lot of experience in the process of producing semi-trailers. Today, let's analyze the reasons and solutions for the automatic locking of semi-trailers. Some of them are our own primitive methods. If you can understand why, it might save you now and in the future. A lot of time and a lot of money, add it if you're an expert.
If you are a tow truck driver, have you ever encountered a trailer moving and then the brakes slowly lock up, can you slam on the brakes a few times, or just release the handbrake and then the brakes won't work? Let's talk about the gas path of the semi-trailer first. The tractor has two spring air pipes leading to the trailer, a red one, and a green (yellow) red one for normal ventilation. Keep the semi-trailer gas cylinder consistent with the main vehicle (air pressure). If some vehicles fail during maintenance, please disassemble the air duct to distinguish. The other air pipe is the brake air pipe, which is the same for the handbrake and footbrake. Please pay special attention when driving or when the handbrake and footbrake have no braking effect, there is no air.
Semi-trailer braking principle, open the air valve through the handbrake or footbrake. When the air pipe reaches a certain pressure, the air connection advance relay valve is opened, and the rear axle is braked. When the vehicle is driven for a long time, there are impurities in the gas cylinder, aging of the pipeline, etc., and the air pressure will leak to the brake air circuit through the manual valve that is not tightly closed. When a certain pressure is reached, it will automatically brake, and the foot brake is also possible, but many riders and friends have never encountered it (because only the manual valve and the foot control valve may leak into the brake air circuit, and the other may be excluded).
Solution: replace the manual control valve (don't listen to the repairman to change this valve, that valve will waste people and money) if it still can't be solved, disassemble the brake air pipe to see if there is any air leakage (some parallel inlet parts leak water when they are new ) If not, check whether the foot control valve leaks. If there is no auto parts store on the road, you can use a very simple and practical method, that is, use a lighter to heat the nails, and poke a small hole in the brake air pipe, so that the air pressure leaking to the air pipe is zero (because the leak is slow), the problem is solved,