The first thing to do is to cut off the power. Before the power is cut off, the ignition switch should be turned off. At the same time, the electrical equipment, such as audio equipment, should be turned off. The specific power-off sequence is as follows: safety first, so in maintenance, first pull out the negative pole, and then pull out the positive pole. When installing, the sequence is the opposite, first install the positive pole, then install the negative pole. Some friends will ask: why cut off the negative pole first? Here, I'd like to explain to you:

1、先拆正极存在烧坏电器元件的风险，容易引起电脑板烧毁的损失。在电路的实际维修过程中因违反操作规程，损坏电路和把手烧伤的人很多，因为蓄电池正负极短路电流非常大，能瞬间产生高温。

1. First remove the positive electrode, there is a risk of burning out the electrical components, which is easy to cause the loss of computer board. In the actual maintenance process of the circuit, there are many people who damage the circuit and burn the handle because of violating the operation rules. Because the short-circuit current of the positive and negative electrodes of the battery is very large, it can produce high temperature instantly.

2、如果先拔掉正极，因负极是搭铁的，也就是正极周围的金属车体都是负极，如果用工具拆卸正极接线时，工具碰到旁边的金属车体，就会造成蓄电池正负极短路。

2. If the positive pole is pulled out first, because the negative pole is grounded, that is, the metal body around the positive pole is all negative pole. If the tool touches the metal body beside the positive electrode when removing the positive connection with a tool, it will cause a short circuit between the positive and negative poles of the battery.

3、如果先拔掉负极，因负极周围的金属车体与负极是连通的，即使工具碰到也不会产生什么坏的结果，当负极拔掉后已经断电，再去拔正极就不会有什么危险了。

3. If you pull out the negative pole first, because the metal body around the negative pole is connected with the negative pole, even if the tool touches it, it will not produce any bad results. When the negative pole is pulled out and the power has been cut off, it will not be dangerous to pull the positive pole again.

在这里要注意一点：现行的搅拌车的蓄电池都是有总开关的，但是原来的都没有，就不好操作；而且如果是危险品运输车，比如油罐车，车上的行车记录仪是不允许断电的，断电后行车记录仪不能工作，车主可能就要承担法律责任了，但是我觉得如果是危险品运输车，可以在车上放置一个供行车记录仪的备用电源，这样即使电路出现故障，也不于让行车记录仪断电了。如果你的搅拌车电路出现问题，一定要注意以上这些问题哦！

Here we should pay attention to one point: the battery of the current mixer truck is equipped with a master switch, but the original one is not available, so it is not easy to operate; moreover, if it is a dangerous goods transport vehicle, such as an oil tank vehicle, the vehicle's tachograph is not allowed to be powered off. After the power failure, the vehicle owner may have to bear legal responsibility, but I think if it is dangerous goods transportation A backup power supply for the tachograph can be placed on the car, so that even if the circuit fails, the tachograph will not be cut off. If your mixer circuit problems, must pay attention to the above problems Oh!