How to test relays with a multimeter

Take the leads of the multimeter and connect them across the coil terminals of the relay. For a normal coil, the multimeter should read anywhere between 40Ω to 120Ω. If the coil is damaged i.e., it is open, the meter shows out of range and you have to replace the relay.

1. How do you check if a relay is bad?
2. How many Ohms should a good relay have?
3. How do you tell if a relay fuse is blown with a multimeter?
4. What pins do you test on a relay?
5. How do you manually test a relay?
6. What are the common faults of relays?
7. What are the 4 pins on a relay?
8. How many volts should a relay have?
9. How do you check if a relay is shorted?
10. How do you measure relay resistance?
11. Does a relay have resistance?
12. How much current does a 12v relay coil draw?
13. What numbers mean what on a relay?
14. What is A1 and A2 on a relay?
15. How many ohms should a 24V relay have?
16. How do you identify a relay?

How do you check if a relay is bad?

Grab a multimeter and set it to Ohms. Touch the leads across the electromagnet coil pins and measure resistance. Anywhere from 50-120 ohms is OK. Out of range or open means a bad electromagnet coil winding and time for a new relay.

How many Ohms should a good relay have?

The electrical resistance (impedance) of the coil is vary and is different depending upon the manufacturer of the relay as well as relay's type, but in general a typical value should be expected between 50 ohms and 200 ohms.

How do you tell if a relay fuse is blown with a multimeter?

If you're using a digital multimeter set to measure resistance, touch the probes together to get an initial reading. Then put the probes on either side of the fuse and check if the reading is similar. If it is, then the fuse works properly. If you get no reading or “OL”, then the fuse has blown.

What pins do you test on a relay?

To see if your relay is in good condition with a multimeter, we test the continuity and resistance between the two normally closed pins and the two normally open pins. Set the meter to measure resistance by putting it in the Ohms setting.

How do you manually test a relay?

Take the leads of the multimeter and connect them across the coil terminals of the relay. For a normal coil, the multimeter should read anywhere between 40Ω to 120Ω. If the coil is damaged i.e., it is open, the meter shows out of range and you have to replace the relay.

What are the common faults of relays?

The two most common failure mechanisms of relays are contamination and mechanical wear of the internal switching elements discussed as follows: a. Contamination is a major cause of early life failures.

What are the 4 pins on a relay?

4 Pin Relay

4 pin relays use 2 pins (85 & 86) to control the coil and 2 pins (30 & 87) which switch power on a single circuit. There are 2 types of 4 pin relay available; normally open or normally closed. A normally open relay will switch power ON for a circuit when the coil is activated.

How many volts should a relay have?

The nominal voltage of a 12V relay is 12V, so 80% of this is 12 x 0.8 = 9.6V. So in theory, this relay should activate at 9.6V.

How do you check if a relay is shorted?

Use an ohmmeter to check solid-state relays.

When solid-state relays start to short, they will almost always fail. Solid-state relays should be checked with an ohmmeter across the normally open (N.O.) terminals when control power is off.

How do you measure relay resistance?

Standard Method For Measuring Contact Resistance

Set the DVM to measure Voltage. Turn on the coil power supply to energize the coil and engage the contacts. The reading on the DVM is the Voltage Drop across the contacts. However, since the load is 1A and Ohm's Law says that V = IR, then V = R.

Does a relay have resistance?

Like for automotive applications, the relay coil resistance is mostly in the 50 ohms – 200 ohms. For 24V systems, the coil resistance can be as high as 200 ohms to 600 ohms.

How much current does a 12v relay coil draw?

The current draw of the coil is not normally shown but is typically 150-200 mA with a corresponding coil resistance of around 80-60 W. Tip: Knowing the coil resistance is useful when testing the relay for a fault with a multi-meter.

What numbers mean what on a relay?

Numbers of a Relay

Note that each pin is numbered. 85 and 86 are the coil pins while 30, 87, and 87a are the switch pins. 87 and 87a are the two contacts to which 30 will connect. If the coil is not activated, 30 will always be connected to 87a. Think of this as the relay in the Normally Closed (OFF) position.

What is A1 and A2 on a relay?

What Do A1 and A2 Mean on a Contactor? A1 and A2 on a contactor typically refer to either end of the electromagnetic coil assembly. Most contactor manufacturers use A1 and A2 to designate the two terminals connecting electrical power to the contactor's magnetic coil.

How many ohms should a 24V relay have?

Like for automotive applications, the relay coil resistance is mostly in the 50 ohms – 200 ohms. For 24V systems, the coil resistance can be as high as 200 ohms to 600 ohms.

How do you identify a relay?

Relays can look very similar from the outside so they normally have the circuit schematic, voltage rating, current rating and terminal numbers marked on the body to identify them. This shows the basic internal circuits (including any diodes, resistors etc.) and terminal layout to assist wiring.