Fiat Bravo Quiz
Electrical system

Check relay

In this manual: Electrical system
Dear Reader — 1Engine — 35Engine lubrication — 3Engine cooling — 10Ignition/spark plugs — 14Fuel system — 10Petrol fuel injection — 13Diesel injection system — 13Exhaust system — 7Clutch — 7Transmission / Gearshift / Automatic Transmission — 5Front Axle — 11Rear axle — 4Steering — 9Wheel alignment — 1Brake system — 22Wheels and tyres — 10Body — 34Heating — 6Electrical system — 39Lighting system — 14Instruments — 7Windscreen wiper system — 8Vehicle care / tools — 6Jump Starting / Towing the Vehicle — 3Jacking up the vehicle — 1Fiat Bravo / Brava Maintenance Schedule — 1Maintenance — 38Wiring diagrams — 5
~2min read

Many circuits incorporate a relay. A switching relay works like a switch. Example: when the high beam is switched on via the hand switch, the relay receives the command to switch current through to the high beam.

Of course, the current could also be routed directly from the battery to the high beam via the light switch. However, for all consumers with high current draw (headlights, windshield wipers, fog lights), a relay is inserted in between, so as not to overload the switch and to keep the current paths short.

Checking switching relay

When the consumer concerned is switched on, the relay is activated: the switching current energizes a solenoid inside the relay, which pulls in a contact and so closes the circuit for the "working current". The working current continues through the relay to the electrical consumer.

The easiest way to check a relay's function is to replace it with a known good one, as is done in workshops. Since the home mechanic rarely has a new relay immediately available, the following procedure is recommended for so-called switching relays, such as those used to switch fog lights and main headlights, among other things. The terminal designations given here may also differ, especially for relays fitted as standard equipment.

  • Pull the relay out of its holder.

  • Switch on the ignition and the corresponding switch.

  • First use a voltage tester to determine whether voltage is present at terminal 30 (+) in the relay holder. To do this, connect the voltage tester to ground (-) and carefully insert the other probe into terminal 30. If the LED of the voltage tester lights up, voltage is present. If the voltage tester shows no voltage, trace the interruption from the battery positive terminal (+) to terminal 30 using the wiring diagram.

  • Make a jumper wire from one piece of insulated wire; the ends must be bare.

  • Use this jumper in the relay holder to connect terminal 30 (battery +, always live) with the output of the relay normally open contact, terminal 87. This step does practically exactly what an intact relay would do. The terminal positions in the relay holder are shown on the relay or on the plug contact.

  • If, with the jumper inserted, the high beam for example lights up, the relay can be assumed to be defective.

  • If the high beam does not light up, check whether the ground connection to the headlight is intact. If so, trace the interruption in the wiring from terminal 87 to the main headlight using the wiring diagram and repair it.

  • If necessary, install a new relay.

Warning: if a fault occurs only intermittently in a circuit that is fitted with a relay, the defect is usually in the relay. In this case, a contact in the relay sticks from time to time, while the relay works correctly the rest of the time. When the fault occurs, tap lightly against the relay housing. If the relay then switches through, replace the relay.

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