So Fix it

Automotive wiring systems arent the simplest thing on the planet, but they arent the most complicated either. When you break the electrical system down into its component parts, you find that it consists mainly of simple circuits and equally simple switching gear. Relays are one type of electrical switch that manufacturers install to minimize production costs and maximize safety.

Electrical Basics

A relay is essentially a switch that you dont have to flip. Electricity is the movement of electrons, and moving things, by definition, have an origin and a destination. Think of electrons like cars on a racetrack that move around it at the speed of light; if you suddenly remove a section of track, then the race stops because all the drivers fall into the hole and get smashed into atoms. Electrical circuits work the same way. As long as the circuit or track stays intact, the electrons can continue their race.

Relay Basics

A relay is basically just a switch that you dont have to flip, and a switch is a means of removing a section of the circuit. When you flip a light switch to the On position, its internal connections close the circuit and allow electricity to flow through it. Now, imagine the switch lever is made of metal instead of plastic and youre standing next to it with a magnet. Using the magnet, you can flip the switch on and off without touching it. But moving the magnet isnt practical, so what you need is a magnet that you can leave in place but turn on and off.

Induction Coils and Electromagnets

Anything moving through a gravitational field produces a magnetic wake, and it doesnt matter if that moving thing is an electron or a Boeing 747. Most metals have small regions of magnetism inside called magnetic domains, but those domains point in all different directions so they cancel each other out. Wrap a coil of wire around a metal rod and send electrons flowing through the wire and you create a magnetic "tornado" around the rod. This vortex gets all of the magnetic domains temporarily pointing in the same direction, turning the metal core into an electromagnet.

Relay Construction and Function

Youve undoubtedly connected the dots by now: a metal armature arm inside the relay is spring-loaded to stay open, but when the electromagnet under it activates, the armature comes down and closes the circuit. The idea behind using a relay is that it takes far less current to energize the electromagnet than the circuit would normally use. That means that, although your starter may require 50 amps of current to spin the motor, your ignition key mechanism only needs to pass 0.50 amps to energize the magnet. This allows manufacturers to use thinner-gauge wire and lighter-duty switching gear without risk of frying the wire or the switch.

Replacing the flasher relay on your Volvo 850 can be done very quickly and requires no tools. The flasher relay routes the power from the turn signal switch to the turn signals, converting the flow of electricity from a solid stream of power to an alternating stream, which causes the lights to flash on and off. If the relay fails, you can replace it with a new one, available from any auto parts store or through your Volvo dealer.

Instructions

1

Open the hood of your Volvo and locate the fuse box on the drivers side of the engine compartment up against the firewall. Open the plastic lid by releasing the locking tab on the drivers side of the box then swing the lid towards the passengers side.

2

Locate the flasher relay on the drivers end of the box, grasp it by the sides and pull it straight out. Discard the old flasher and install a new one by pushing it straight into the fuse box where the old one came out.

3

Close the lid, snapping the locking tab in place. Close the hood of the car and test the repair by turning the ignition on and activating the turn signals, one side at a time.

Turn signals are lights located at or near the exterior corners of all cars, including the Chevrolet Lumina, that signal the drivers intention to turn. The driver activates either the left or right turn signals via a switch usually found on the steering column. The turn signal lights blink, thanks to a module in the turn signal electrical circuit called a flasher. Sometimes, this flasher malfunctions or wears out. As a result, the turn signals either wont flash or wont come on at all.

Instructions

Test the flasher

1

Have an observer stand near the back of the vehicle so they can see both turn signal lights.

2

Engage the parking brake if you havent done so already.

3

Start the car.

4

Apply the brakes. If the observer sees the brake lights working correctly, proceed. If one or both brake lights dont work, you must troubleshoot the brake-turn signal circuit or refer the problem to a certified automotive technician.

5

Activate the turn signal, first in one direction then the other. If the observer doesnt see the turn signal lights flash on either side, replace the flasher.

Replace the flasher

6

Turn off the car.

7

Find the flasher. The flasher is a cylindrical module approximately 1-inch diameter by 1-inch long, plugged into a connector. The flasher is found beneath the driver side dash, near where the steering column passes through the firewall.

8

Unplug the old flasher from its socket.

9

Install the new flasher.

10

Perform the Step 1 test to ensure the new flasher works properly.

An automotive horn is an important safety component used to alert drivers and pedestrians. The horn system in most vehicles is comprised of three primary parts: the horn, the switch and the horn relay.

Purpose

When the horn switch in the steering wheel is activated, the switch sends a signal to the horn relay. The horn relay then sends an electrical current to the horn, producing its sound. The horn relay allows a smaller charge to run through the switch.

Horn Relay Location

Often, the most difficult part of troubleshooting a horn relay is finding it. The horn relay may be located inside the fuse box under the hood, integrated into a larger electrical box or is a separate unit. If the horn relay is not easily located, follow the wiring back from the horn to find the relay or refer to a vehicle-specific shop manual.

Troubleshooting the Horn Relay

When a horn suddenly stops working, the first thing to check is the horn fuse. If the fuse is fine, the horn should be tested. You can do this by running a small jumper wire from the battery to the horn. If the horn sounds, the relay is most likely defective. If the horn does not sound, it needs to be replaced.