Toyota RAV4 > Chassis electrical system > Relays — general information and testing

Relays — general information and testing

General information

1. 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 (the control circuit) to open and close a high-current circuit (the power circuit). If the relay is defective, that component will not operate properly. Most relays are mounted in the engine compartment fuse/relay boxes, with some specialized relays located above the interior fuse box under the dash (see illustrations). If a faulty relay is suspected, it can be removed and tested using the procedure below or by a dealer service department or a repair shop. Defective relays must be replaced as a unit.

i. 1a the cover for the engine compartment fuse/relay box (left-hand side of the engine compartment) has the relay and fuse location chart printed on the inside of the lid

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i. 1b the number 2 relay box (right-hand side of the engine compartment) is marked under the lid as well

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2. . Refer to the wiring diagrams for the circuit to determine the proper connections for the relay you’re testing. If you can’t determine the correct connection from the wiring diagrams, however, you may be able to determine the test connections from the information that follows.

3. There are four basic types of relays used on these models (see illustrations). Some are normally open type and some normally closed, while others include a circuit of each type.

i. 3a These two relays are typical normally open types; the one above completes a single circuit (terminal 5 to terminal 3) when
energized — the lower relay type completes two circuits (6 and 7, and 3 and 5) when energized

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i. 3b These relays are normally closed types, where current flows though one circuit until the relay is energized, which interrupts
that circuit and completes the second circuit

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4. On most relays, two of the terminals are the relay control circuit (they connect to the relay coil which, when energized, closes the large contacts to complete the circuit). The other terminals are the power circuit (they are connected together within the relay when the control-circuit coil is energized).

5. Some relays may be marked as an aid to help you determine which terminals are the control circuit and which are the power circuit. If the relay is not marked, refer to the wiring diagrams at the end of this Chapter to determine the proper hook-ups for the relay you’re testing.

6. To test a relay, connect an ohmmeter across the two terminals of the power circuit, continuity should not be indicated (see illustration). 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. On some relays, polarity may be critical, so, if the relay doesn’t click, try swapping the jumper wires on the control circuit terminals.

i. 6 To test a typical four-terminal normally open relay, connect an ohmmeter to the  two terminals of the  power circuit — the
meter should indicate continuity with the relay energized and no continuity with the relay not energized

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7. If the relay fails the above test, replace it.



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