How to Use a Multimeter to Find the Fault in an Electrical Control Circuit
There are generally voltage method and resistance method to find line faults. The voltage method is to use the voltage to detect the fault point, and the resistance method is to use the resistance to find the fault. They have their own advantages. If you are not familiar with the circuit, we recommend using the resistance method to judge the fault, which is relatively safe.
The main line has fewer wires, so it is easier to judge the fault. Here we take the control line as an example.
Before measuring the control wiring, disconnect the control wiring power supply/fuse to separate the control wiring from the main wiring. The purpose of this is to avoid interference from the main line when measuring the control line.
Then put one test lead on the odd starting number of the control loop (such as 101), and the other test lead on the even starting number of the control loop (such as 102), and the resistance between them should be infinite. Then press the button switch SB2, then there should be a certain resistance (the resistance is equal to the coil resistance). If the resistance value is still infinite, it means that there is no communication between the two test leads, and a certain place is broken, then continue to search.
If you don't have time to press the button, we can use short wires or other metal objects to short-circuit the button, and then remove it after testing.
Then we press the button again and measure the next terminal of the starting terminal and the even starting number
resistance between. If there is a certain resistance value, it means there is an open circuit. If the resistance value is still infinite, it means that there is still an open circuit somewhere, then continue to search.
. . . And so on, until the point of failure is found. . .
Because the numbering rule determines that the mantissa is an odd number and an even number are two different polarity lines, so we measure the terminals ending in odd numbers and the terminals ending in even numbers, and there is usually a certain resistance between them. (Of course, the premise is the same power circuit)
