How to check a relay switch


Here you can get How to check a relay switch and How to Test a Relay.

If a component that’s fed with electricity through a relay (See How car electrical systems work ) terminal of the battery to the feed terminal on the component, thereby bypassing the relay and provide wiring.

If the component still does not work, it’s faulty; if it works, then the availability is faulty and therefore the fault are going to be within the relay or the connections thereto. Trace the supply wire back to seek out the relay — this is often a small metal or plastic box which usually has four spade terminals and is located near the battery.

What Is A Relay?

Relays can be found in nearly any vehicle, and are even used in marine and aviation applications. They’re generally used to allow a low amperage circuit to control a higher amperage circuit. Relays act as a switch, allowing the low amperage circuit to turn the high amperage circuit on or off. 

As an example, imagine your vehicle’s headlights. If you connected the lights directly to the on/off switch in the vehicle’s dash, the amperage could exceed the switch’s capacity, which can cause melting wires and even a fire in some cases. Relays can also control multiple systems at once, such as activating headlights when windshield wipers are turned on, or extending an antenna when the radio is turned on.

Relay Safety

Relay testing is a simple process, but don’t skip out on safety. It’s a good idea to take these things into account when working with relays:

  • If you’ve determined that the relay is malfunctioning and needs to be replaced, it’s not ok to mix-and-match relays from other parts of the vehicle or from a random junk bin in your garage. the incorrect relay can cause a brief or a power surge which will damage your vehicle’s electrical system.
  • Handle the relay gingerly and check out to avoid dropping it. If the relay is broken internally, it can cause burning or melting of wiring. Also avoid modifying the relay in any way.
  • don’t start working with relays or anything involving electricity during a space that contains flammable or explosive gases like gasoline or other fuels.
  • albeit you’re an experienced tinkerer within the garage, check your vehicle’s service manual (not the owner’s manual) to spot and understand the wiring system and relays.

Check a relay switch

A typical charging circuit

The battery is earthed to the body by a brief , heavy cable or by a braided wire strap. On most cars the negative battery terminal is earthed. From the positive terminal another heavy cable goes to the starter solenoid switch, which feeds current to the starter along a 3rd heavy cable. A wire leads from the live side of the solenoid (not through the switch itself) to the ignition switch.

Another wire leads from the live side of the solenoid to the ammeter (if fitted) on the instrument panel. Thus, the ammeter is usually live, and always shows whether any power is being discharged. This circuit is then completed to the generator , in order that current within the other way causes the ammeter to show how much the battery is being charged. From some extent after the ammeter, another wire (not shown) goes to the lighting switches and to the fuse box, where it supplies power for circuits not controlled by the switch.

An ignition-controlled circuit

If the car circuits might be accidentally left ‘live’ when the car isn’t running, the battery would be discharged unnecessarily. For this reason, most circuits are operated through the ignition switch. (The exceptions are those which could be needed for safety – chiefly headlamps, sidelights and emergency flashers.)

From the switch a clear wire runs to the fuse box, where it’s connected to the fuses of all those circuits which come on with the ignition. From each fuse a clear wire runs to every of the circuits, picking up a trace colour after its first connection.

How to Test a Relay

When you suspect that something goes wrong with one of the relays in your vehicle you’ll take it to a mechanic to urge it verified or you can go through the method of getting the relay tested on your own. testing your own relays isn’t overly complicated and if you’re comfortable doing any add your vehicle, you’ll be ready to handle this job on your own.

Step 1: you ought to use a test light and check the fuses in your vehicle before you proceed with checking the relays just just in case the matter is with a couple of instead of the relay burning it. Every electrical component will have a fuse within the system also that you can check and replace if necessary. Automotive fuses are typically rock bottom and will cost you under $10.

Step 2: If you check under the hood of your car you should have something called a power distribution centre or PDC. This provides a map for relay locations and what all does. this may be handy for you to seek out the exact relay you need to address whatever problem you’re experiencing with your vehicle. If you do not have a location map for all the relays in your vehicle on your PDC anywhere, you’ll inspect your owner’s manual and it should provide an equivalent information. If that fails, the web will certainly have what you’re looking for so you’ll Google your make, model, and year and therefore the relay you are looking for and you ought to be ready to find exactly where you would like to travel .

Step 3: Now that you’ve got located the precise relay that you’re looking for, gently take hold of the relay that you are looking for and have someone turn the vehicle on. All you would like to do is hold the relay between your fingers, there is no got to pull thereon or move it. because the engine cranks over, the relay should click in one among the switch positions. If that happens, then you know this relay is working properly. If it doesn’t happen, then you would like to proceed.

Step 4: close up your car and now you’ll remove the relay to inspect it at now . Get a firm grip thereon and pull forward, offer you a touch of a wiggle if you would like to assist it begin .

Step 5: Give the relay a fast visual inspection. The terminals on the underside should be clean. If you see any signs of corrosion or damage from heat, you are going to require to replace the relay.

Step 6: you need to do an inspection of the terminal that the relay came out of. The terminals are encased in plastic, so if there’s been a problem with overheating you’ll see some melting or evidence of burning around them. That also indicates you would like to exchange the relay. If you’re seeing just a touch of mild corrosion, you’ll use an abrasive tool of some kind to scrape the corrosion clean and provides it a good buff in order that it’s in proper working order again.

Step 7:  The relay should show an illustration of the internal circuit that it applies to. On the primary side of a relay you’re going to find terminal 86 and 85.  Power from the switch comes into the relay at pin 85 and it heads out to the ground at pin 86. That makes the complete circuit activating the electromagnet. The magnet closes the second circuit in the relay that runs from pin 87 to pin 30.

High amperage current from the battery enters the relay at pin 87. Pin 30 is where the current flows to whatever component it controls. 

Step 8:  To check any relay to make sure it’s working properly the only tool you really need is a multimeter. Once you have the relay removed you can set the multimeter to measure DC voltage and check to see if there are 12 volts located at pin 85 in the fuse box where the relay plugs in. If there is no voltage there you need to check the appropriate fuse for whatever component that you are checking.  

Step 9: If you confirm that there’s voltage in the 85 position then you can turn your multimeter to continuity and check just make sure that you have a ground at the 86 slot. If that is in good working order, then you can move to the 87 and check for voltage there. If you have no voltage present at the 87 point, then you may also have a blown fuse or problem with the circuit breaker.

Step 10: Return the multimeter to the continuity function and you can check the 30 terminal by placing one lead there and the other on the component positive voltage connection point. If that looks alright, then the relay is very likely the problem so you can replace it.

Step 11: If you’re not sure that you performed all of the steps properly, it never hurts to do a double check just to make sure everything is working the way it is supposed to be. 


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