When a relay is not working, then the meter will read zero or OL. To test a relay to see whether it is good or defective, the simplest way to do would be to use a multimeter set to the ohmmeter setting and measure various resistance values of the relay. Using a multimeter The only tool required to check a relay is a multimeter. An old analog voltmeter will work too but be careful of polarity when using one of them or you can peg the needle and do permanent damage to the meter movement. Energize the relay. Below is a guide on how to test a 5-pin relay switch. The multimeter works by applying a small voltage to the semiconductors in the relay. Use a digital multimeter (DMM) to test the resistance between each pole of the relay and the corresponding NC and NO contacts for that pole. The second case is more common when fuses break under the influence of some kind of force, while the first case is possible only in situations where the fuse had melted down. Using a Digital Multimeter to Test the Fuel Pump Relay. To test relay coil using multimeter put a multimeter on ohmmeter settings, and measure resistance between coil contact. And one of the best ways to do this is to use a multimeter with an ohmmeter setting and then measuring the resistance values. Turn your multimeter on and set it to the ohms setting. Difficulty Scale: 4 of 10. Now check for continuity between N/O contacts and pole. In our case, we will dwell much on a digital multimeter, which has more advantages over the analog multimeter. When it comes to the second case, I would still test them with the multimeter, though. Probe the main wire leading from the relay with the test light. There are a few things to check. Orient the relay so the middle -- noted "87a" -- terminal post is vertical to you, and the "sideways" 30/51 post is on the right. In this article, we will show what resistance readings you should get when you measure various points of a relay. All NC contacts should read 0 ohms to the corresponding pole. How to Test a Relay with a Multimeter? Unplug the relay from its electrical connector, making sure not to break the locking tabs on the relay. First, how these little beggers work: The flasher has a bi-metal strip in it. I have been using the LM741 and LM358 for donkeys ages now and I always use the below method to check if these guys are working as they are supposed to. A digital multimeter (DMM) is one of the most useful test instruments in any automotive electrician's tool kit. For this test it is recommended for you to have a dual power source, but it is not mandatory. Therefore, because this item the battery last longer. In order to Test a Capacitor using Analog Multimeter, we are going to use its Ohmmeter functionality. NC and NO pin. The only tool required to check a relay is a multimeter. Use these tips to learn how to test a 4 terminal relay. Listen for the multimeter to beep continuously as you hold the probes against the fuse. First, disconnect all wires to the relay, making sure you know which wire goes where before you disconnect them. Check resistance of the coil. If you’re using a digital multimeter set to measure resistance, touch the probes together to get an initial reading. Disconnect the wires at their corresponding components at both ends using a screwdriver. They come in handy for many car and home troubleshooting tasks. OK, it's time to get our hands dirty and bench test the relay. As a final test, measure the resistance of the relay coil using a multimeter and check whether it is matching to the value stated by the manufacturer. You still can use a digital multimeter for the same purpose. Yes dear, you can use a multimeter to check if you op-amp is working properly. With the relay removed from the fuse box, the multimeter set to measure DC voltage and the switch in the cab activated, first check to see if there are 12 volts at the 85 position in the fuse box where the relay plugs in (or wherever the relay is located). It tests the NPN transistor; if it is faulty, it shows 0, but if the silicon transistor is working, it shows 0.7 and 0.5 for a germanium transistor. Current flows through the flasher, through the light bulb and back to ground. As mentioned in the previous page, you'll need three very important things: A Multimeter (analog or digital). … Connect a jumper wire between one wire end and the car frame. All NO contacts should read infinite resistance to the corresponding pole. Switch the ignition key off. Step 5. If you don't have a digital multimeter, though, buy one. Maybe a helper. Step 1 . Easy step by step procedure to test an automotive relay, this information pertains to all relay controlled circuits. DMMs and analog ohmmeters are available in electronic parts and hobby stores. Energize the relay. The switch in the can is normally closed. All NC contacts should read 0 ohms to the corresponding pole. Assess for 12 volts within the 85 position on your fuse box; once the voltage is present, you should set the multimeter to continuity mode and assess the 86th slot if it has an excellent connection to the ground. Testing continuity in a wire, current, or fuse is a good idea if you’re installing or repairing any electrical components in an outlet, fuse box, car, or appliance. if the bulb lights, it means the relay is working. Use a digital multimeter (DMM) to test the resistance between each pole of the relay and the corresponding NC and NO contacts for that pole. As usual, disconnect the capacitor and discharge it. If you can’t see anything wrong with the fuse, but you want to be sure, you can use your multimeter. In the above video, Purkeys National Truck & Fleet Representative, Larry Rambeaux, demonstrates how to test resistance on a 5-pin relay using an ohmmeter. Typically these data will be printed on the larger relay case. Using a multimeter. The indication of the multimeter should basically match the coil resistance of the relay. A multimeter is a convenience. If the light glows, there is incoming voltage. Conversely, a relay that is in good condition should give a result of 0.5 or 0.7 depending on the type of relay. 5. With most fuses, you’ll be able to see when it’s defect. The reading should be open (infinite ohms) on an NO relay and short (0 ohms) on an NC relay. Another way to test for resistance by use of a wire jumper. But, more likely you won't be testing relays that often, so probably you don't want to buy a relay tester. The multimeter is placed in the “R×100” or “R×1k” gear, and the two test leads (regardless of positive and negative) are connected to the two pins of the relay coil (shown in Figure 5). Check for a broken or ‘burned’ look. For that, we need a relay datasheet, in which all relay detail described. it's pin configuration like a number of pins, on which pin relay coil is connected. Place the meter's test wires across the power and control terminals. Step 2. The main reason for testing a relay is to find, whether it is good or defective one. You'll need a power source to activate the relay (during the test) and this power source will be your vehicle's Battery. In this case, you need to have the diode reading to test this type of relay. Otherwise, the relay is not receiving voltage. Use an independent voltage source appropriate for the rating of the relay coil. 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