Toyota 90987-02006 Relay Assembly

Some of the electrical fittings in the car include; fuel injection system, horn, starter, and fog lamps which uses relays to send eletrical signals to parts; they feature a low current control circuit to run a high current power circuit. A bad relay will result in the improper functioning of the connected device and majority of relays are usually placed in the fuse and relay compartment of a car engine. If a faulty relay is assumed to be causing the problem it can be withdrawn from use and diagnosed maybe by a specific test or by a servicing outlet. Defective relays have to be replaced in toto ; circuit identification is usually to be found on a label on the top of the relay or, in the case of some boxes, on the inside of the lid. There are some which are involved with the interior fuse box and among them is the starter relay among others. After wiring diagrams have been made, testing is done by ensuring wiring diagram has been well connected; if in doubt more information can be sought. Some of the common relay classifications are basic relay types and their function, normally closed and normally open. Usually terminals 1 and 3 are of control circuit and are connected to the relay coil and terminals 2 and 4 of power circuit. Certain relays may be labeled for control side and power side terminals. To check, attach an ohmmeter between the power circuit terminals; should read no current flow when not powered but when powered, a current flow should be read. With the jumper wires, join one of the control circuit terminal to the positive terminal of the battery, and another end to the negative terminal; the relay should emit a sound as though it has been 'clicked'. If polarity is important, you may have to interchange the jumper wires or use those with appropriate polarity. An indication that relay is defective is if it fails this particular test, then a replacement is necessary.