Toyota 28300-10020 Relay Assembly, Starter

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Several electrical accessories in the vehicle, such as the fuel injection system, horns, starter, and fog lamps use relays to transmit the electrical signal to the component. Relays use a low-current circuit to open and close a high-current circuit. If the relay is defective, that component will not operate properly. Most relays are mounted in the engine compartment fuse/relay box, with some specialized relays located in the underhood box at the right fender. On some models, the ABS relays are located in a separate underhood relay box at the left side of the radiator. If a faulty relay is suspected, it can be removed and tested. Defective relays must be replaced as a unit. Identification of the circuit the relay controls is often marked on the top of the relay, but the decal or imprint inside the cover of the relay box should also indicate which circuits they control. To test a relay, connect an ohmmeter across the two terminals of the power circuit. Continuity should not be indicated. Now connect a fused jumper wire between one of the two control circuit terminals and the positive battery terminal. Connect another jumper wire between the other control circuit terminal and ground. When the connections are made, the relay should click and continuity should be indicated on the meter. If the relay fails the test, replace it.

If any of the relay tests fail, it's advisable to replace the relay with a new one to ensure proper functioning of the associated accessory.

If a relay is defective, the component it controls will not operate properly.

If a faulty relay is suspected, it can be removed and tested by a dealer or other qualified shop.

Most relays are mounted in the engine compartment fuse/relay box.

Refer to the wiring diagrams for the circuit to determine the proper connections for the relay you're testing. If the correct connection cannot be determined from the diagrams, additional information may help.

Most relays are mounted in the engine compartment fuse/relay box, with some specialized relays located in the underhood box at the right fender.

Fuses are designed to break a circuit when a predetermined current is reached, in order to protect the components and wiring which could be damaged by excessive current flow. Any excessive current flow will be due to a fault in the circuit, usually a short-circuit.

To test a relay, connect an ohmmeter across the two terminals of the power circuit (continuity should not be indicated). Then, connect a fused jumper wire between one control circuit terminal and the positive battery terminal, and another jumper wire between the other control circuit terminal and the ground. The relay should click and continuity should be indicated on the meter. If it doesn't click, try swapping the jumper wires on the control circuit terminals.

You may be able to determine the test hook-ups from the information provided in the testing section.

Connect a fused jumper wire between one of the control circuit terminals and the positive battery terminal, and another jumper wire between the other control circuit terminal and ground. The relay should click when the connections are made.

If any of the relay tests fail, it's advisable to replace the relay with a new one to ensure proper functioning of the associated accessory.

Relays use a low-current circuit (the control circuit) to open and close a high-current circuit (the power circuit).