A mechanic and truck driver for more than 40 years, Lowell is able to write knowledgeably on many automotive and mechanical subjects. A 12-volt circuit is usually connected to a battery or a transformer. A 12 volt relay is an important component in the electrical system of modern cars and trucks. Step 2 - Next, reinstall the relay while keeping the wire strand inserted and clear of any other terminals or metal (ground). Fortunately, a car relay is easy to test. Test the relay’s voltage at the switch. For example, a low power circuit in a car that commands the high power headlights to come on would send the command through a 4 terminal relay. For your battery to pass a load test, the multimeter must read between 9.5 to 10.5 volts straight for 30 seconds when the battery is tested. The magnet closes the second independent circuit within the relay that runs between pin 87 and 30. K.K. Disconnect Relay How to test a car relay with a 9v battery. Check for 12 volts at the relay input to the coil with the meter’s negative on the frame of the vehicle. The relay draws very little power to perform the switching, a Test for continuity between terminals 30 and 87. There should be continuity between these terminals. Check for continuity between terminals 30 and 87. If the vehicle won’t start, check for a strong click from the relay when it is initiated. Check the starter relay wiring one more time and then test by attempting to start the vehicle. So it is crucial to test a relay if it stopped working before you replace it or throw it away. How To Test A Relay Using Multimeter & Battery? Bad contact points can cause a voltage drop. A 12 volt relay is an important component in the electrical system of modern cars and trucks. The set of contacts that are open when the relay is not energized are called normally open (N/O) contacts and the set of contacts that are closed when the relay is not energized are called normally closed (N/C) contacts. A continuity tester is a battery operated device that either lights up or buzzes when a circuit is continuous. When the ignition relay is faulty then the battery power is still drawn by the ignition system even after turning off the ignition. There should now be continuity between these terminals. Use these tips to learn how to test a 4 terminal relay. Testing a 12 volt relay is easy and requires a minimum of tools and time. Connect the other alligator clip to the remaining trigger, and place its free end on a 12V source. If the relay passes all the tests it is good and the problem exists elsewhere in the fuses or vehicle wiring. Testing a car relay involves the use of a 12-volt source, such as a car battery, and a multimeter that is capable of reading resistance. Relays switch the power to high current drawing devices to minimize the distance that large gauge wires must run to cut down on weight and cost. Depending on the circuit it controls, ... Connect a jumper wire between the battery positive terminal and one of the control circuit terminals on the relay. Troubleshoot any particular relay in your car and find out whether you actually need to replace it. Never attempt to test for continuity when the relay is plugged into the vehicle. It depends on what you want to test (since you said “test”). In this post, I am going to teach you how to test a relay with a multimeter . How To Test A Relay With A Multimeter. Connect a test lead from relay terminal 85 to the positive terminal of the 12 volt battery. And one of the best ways to do this is to use a multimeter with an ohmmeter setting and then measuring the resistance values. Generally these two terminals will be the smallest terminals on the relay. This article shows you how to test a relay. The battery could be unintentionally depleted by an accessory device that was left … There should be continuity between these terminals. Try the switching the + and – positive and negative terminals if … 12 volt relais, relay image by Sascha Zlatkov from Fotolia.com. Squeeze the clip to open it and release it to attach to the terminal and battery. Lowell is a freelance writer who has been writing professionally since June 2008, with articles appearing on various websites. The relay prevents electrical accessories from draining energy by disrupting the power supply. He is currently pursuing a degree in English. Just place the battery on the relay terminals that are connected to the relay coil. When you place the 9 volts battery on the relay coil terminals, the relay will click. Most modern multimeters are autorange, meaning they set the proper range once you begin the test. The relay will close, and you should get continuity between the two pins that the meter is connected to.You should also hear a clicking noise coming from the fuel pump relay. Auto Repair & Mechanics : How to Test a Car Relay - YouTube If one or both of the voltages are not present then you need to check your electrical circuit because it is likely the problem lies there. You may find another relay in your car with the same configuration — arrangement and number of terminals — as your fuel pump relay. Step 1 - To test for intermitted relay failures which are common, remove the relay in question, take a small wire strand, about two inches long and insert it into the relay connector terminal 87 or 30. Replace the relay if any of the continuity tests fail. Sometimes, but rarely, relays do fail. You want to use either a 12V battery or voltage regulator to test the relay. I want to test a pretty common relay with 12 Volts but I dont know if its safe to use the car battery, isnt that too much Amperage? Pin 87 is where high-amperage current from the battery enters the relay. There should not be continuity between these terminals. If the component still does not work, it is faulty; if it works, then the supply is faulty and the fault will be in the relay or the connections to it. Connect the wire between the battery lead and the ignition circuit lead. Determine relay number and pin out. At best you will get false readings, at worse you will damage or destroy your tester. Test the Relay Contacts using Multimeter: Beside that technique of finding the relay functionality, you can use this method also. It came off a Nissan Sentra 99 Could i make 12v battery low voltage disconnect with relay and resistor? Using a relay also means a lighter duty switch is used, further cutting cost and weight. best way to test a relay is remove it from board, get a 9v square battery and touch the switching terminals on the relay, the relay should click if its working. Using the continuity tester, test for continuity between relay terminals 85 and 86, which are marked on the relay. If you want to switch with a 9 V battery, use a relay with a 9 V coil, as @BobK implied in post #4. Find out how to listen for clicks and tones that indicate a functioning relay with help from an auto mechanic in this free video on car repairs and mechanics.Expert: J.B. HebertContact: www.wrxtra.comBio: J.B. Hebert is a machinist, metal fabricator, and auto mechanic who has been fixing and modifying all things mechanical for over 20 years.Filmmaker: David Pakman Relays switch the power to high current drawing devices to minimise the distance that large gauge wires must run to cut down on weight and cost. Connect 12 V supply to Control pins on the relay and listen for a physical click (Gross Test). The purpose of testing a relay is to find, whether it is good or bad . Applying a small amount, as low as .2 amps of current to the relay coil closes contacts to feed power to an accessory that requires more current to operate, usually over 20 amps. Place an alligator clip on one trigger and connect the free end to ground. Another way to test for resistance by use of a wire jumper. If the voltage you read is not 12V when the ignition switch is turned on, the starter relay is faulty. Connect a test lead, which is a wire with an alligator clip on each end, from relay terminal 86 to the negative terminal of a 12 volt battery. A relay that passes this test will probably be ok, but if you still suspect the relay you can easily verify finer electrical properties by continuing. I was thinking if put resistor in series with relay coil i could lower current so relay would barely work on 12v but when it drops to 10v voltage after resistor would be so sma… To wire an automotive relay, make at … Test Function 2. Using the continuity tester, test for continuity between relay terminals 85 and 86, which are marked on the relay. Relays switch the power to high current drawing devices to minimise the distance that large gauge wires must run to cut down on weight and cost. Using any settings beyond that would lead to a less accurate result. The test procedure is as follows. Estimating the voltage this way makes the test result more accurate. Or does it matter since the relay is such a simple device? In this technique you check the three contacts of Relay, in these contacts the procedure is same we will measure the resistance of these contact with a multimeter. A relay usually gets damaged due to a number of reasons. Its Terminal Identification & Operation. Connecting a 12V Relay to Arduino: To connect a 12V relay to the Arduino you need the following things: - 1 Arduino - 1 diode for example 1N4007 - 1 NPN transistor for example 2N2222 (in the US) or BC548 (in Europe) - 1 relay for example one with coil voltage 12V and switching vo… The relay test is done with a 213 relay from a Porsche 944 Turbo. Most 12 volt relays operate accessories in a motor vehicle. Check both power supplies to the relay to confirm the presence of 110v AC and 12v DC. The Fastest Way to Test a Fuel Pump Relay or Other Automotive Relays By far, the easiest way to test a suspect fuel pump relay — or some other automotive relay — is to swap the suspect relay with a good one. Touching the probes to each end of a device or circuit automatically tests for continuity. You will notice that even if the battery is new and working fine it is always drained of power especially in the mor… Copyright 2020 Leaf Group Ltd. / Leaf Group Media, All Rights Reserved. Relay should operate properly from this arrangement, and the extra voltage won't harm the LEDs with the 470 Ω resistor limiting the current. If a component that is 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 supply wiring. Connect your ground connection on the power supply to the ground pin on the relay.Touch the power supply's trigger to the input pin. The ignition relay is the bridge between the battery and the fuel system. A 4 terminal relay is used so a low power circuit may engage a high power circuit without risk of damage to the low power control circuit. Connect a test lead from relay terminal 85 to the positive terminal of the 12 volt battery. When the coil is energized, the NO terminals, close and let electricity flow. Any reading of voltage below 9.5 volts, or if the battery holds a good record for a while and steadily drops, or even when it falls instantly to 0 volts, then it means there is a problem, and the battery should be replaced due to its low capacity . Power from the switch flows into the relay at pin 85 and out to a chassis ground from pin 86, making a complete circuit that activates the relay’s electromagnet. Connect a test lead, which is a wire with an alligator clip on each end, from relay terminal 86 to the negative terminal of a 12 volt battery. You should feel and hear the isolator click and the meter should read 0 ohms. Could an AC/DC adapter at 12 Volts x 1 Amp work also? Step 1. Grasp the relay firmly with your fingers and pull it straight up out of its socket to remove it from the vehicle. If these currents are present then the relay is definitely the problem. Squeeze the clip to open it and release it to attach to the terminal and battery. 1. In this article, we will show you “how to test a relay“. If an open load is observed, test the triggers by disconnecting the wires going to them. A relay will usually have a coil, pole terminal and a set of contacts. Find the particular relay you want to test. Connect a test lead, which is a wire with an alligator clip on each end, from relay terminal 86 to the negative terminal of a 12 volt battery. As the name implies, a battery protection relay keeps the battery from becoming discharged. A 12 volt relay is an important component in the electrical system of modern cars and trucks. The relay draws very little power to perform the switching, allowing the wires carrying the control voltage to be very small. For example, if you have a 12V battery, test it using the 20V setting. One more time and then test by attempting to start the vehicle the resistance values appearing on websites... ” ) your car and find out whether you actually need to replace it or throw it away read... 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