Fuses and Diodes (Wiring diagrams)

Fuses and Diodes

Fusible links (a) and current rated fuses (b) are drawn as shown.

Diode (c) current flow is shown by the direction of the arrow. Zener type diode (d) - prevents voltage passing until a precise value is reached.

REPAIR PROCEDURES FOR WIRING HARNESSES

Introduction

1. Verify the complaint

Turn on all the components in the problem circuit to verify and check the accuracy of the customer complaint. Note the symptoms, do not begin disassembly or testing until you have narrowed down the problem area.

2. Analyse the wiring diagram

Refer to the relevant wiring diagram of the problem circuit. Familiarise yourself with the circuit and determine how the circuit is supposed to work by tracing the current path from the power source, through the circuit components to earth.

The problem circuit may be fed from or feed a number of other circuits, and these will be identified on the wiring diagram. Try operating these circuits. If the other circuits work OK then the fault lies in the wiring of the problem circuit only. If several of the other circuits do not work then the fault lies in the wiring shared by those circuits, i.e. a fuse or earth path is a likely cause.

Based on the symptoms and your understanding of the circuits operation, identify possible areas where the cause of the problem may be found.

3. Isolate the problem by testing the circuit

Make circuit tests to check the diagnosis you made in step 2. Keep in mind that a logical, simple procedure is the key to efficient fault finding. Test for the most likely cause first. Try to make tests at points that are easily accessible.

4. Fix the problem

Once the specific problem is identified make the repair. Be sure to use the proper tools and safe procedures.