How do you test a fuse or relay?
The only tool required to check a relay is a multimeter. 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).
How can you tell if a fuse relay is blown?
Using a multimeter to test a relay fuse is pretty simple. Set the multimeter to Ohms and touch the leads on the electromagnet coil pins to measure resistance. It should be between 50 to 120. If it's out of that range or says it's open, you have a bad electromagnet coil.
How do you test a fuse and relay with a multimeter?
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.
What is the easiest way to test a relay?
1:196:53How to Test a Relay the Correct Way - YouTubeYouTubeStart of suggested clipEnd of suggested clipAnd then we're gonna listen for a click. There we go that's the clear. Okay so most people wouldMoreAnd then we're gonna listen for a click. There we go that's the clear. Okay so most people would stop at this and call this a good relay. But in order to be 100% sure which I strongly recommend.
How do you know a relay is bad?
You want to feel and listen for any clicks. If you feel and hear clicks, the relay works on one side – the side with the energizing circuit and coil. However, if there was no sound from the horn, the relay has a problem along the contact circuit.
How do you test a relay to see if it is bad?
4:498:08How To Test a Relay (and How Relays Work) - in 8 minutesYouTubeStart of suggested clipEnd of suggested clipSo if you're suspecting a bad relay. First thing you can do is perform a click test run a coupleMoreSo if you're suspecting a bad relay. First thing you can do is perform a click test run a couple wires from the battery to the control circuit pins 85 and 86. And see if the relay clicks.
How do you check if a fuse is bad with a multimeter?
0:572:58How to Check For Bad Fuses With A Multimeter - YouTubeYouTubeStart of suggested clipEnd of suggested clipAnd what you want to do just make sure the leads are in the correct locations for ohms. You can testMoreAnd what you want to do just make sure the leads are in the correct locations for ohms. You can test the leads make sure it works should go to zero or close to zero. That's good don't you take a fuse.
Should a relay click?
Actually, unless the relay has a diode in it, it won't matter if the polarity is switched; the electromagnet will be energized regardless. You should hear and feel the relay click. If you don't, the relay isn't working. Replace it.
How do you bypass a relay?
1:332:56HOW TO Bypass A Relay Using One Wire!!! - YouTubeYouTubeStart of suggested clipEnd of suggested clipSay the multimeter shows battery voltage at 12.45 volts that's all that little jumper is doing isMoreSay the multimeter shows battery voltage at 12.45 volts that's all that little jumper is doing is jumping from the 87 terminal to the 30 terminal on the relay.
What causes a relay to fail?
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 causes a relay to fail?
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 comes first fuse or relay?
If you put the fuse after the relay, then that internal short would mean that the live wire from the relay to the battery is not protected. It could then melt and cause a potential fire risk.
How do you bypass a relay?
1:332:56HOW TO Bypass A Relay Using One Wire!!! - YouTubeYouTubeStart of suggested clipEnd of suggested clipSay the multimeter shows battery voltage at 12.45 volts that's all that little jumper is doing isMoreSay the multimeter shows battery voltage at 12.45 volts that's all that little jumper is doing is jumping from the 87 terminal to the 30 terminal on the relay.
Is a relay good if it clicks?
If you hear or feel the relay click, the relay and its wiring aren't the problem. But if it's not clicking, the problem could be in the relay itself or in the wiring.
Test The Coil Terminals of The Relay With An Ohmmeter
We will start with the coil of the relay. A relay coil's resistance always comes with the datasheet of the relay. For example, relay coil resistanc...
Test The Relay Contacts With An Ohmmeter
Besides the coil terminals, you then can check to see if the the other terminals are good as well. This includes the COM terminal, the Normally Ope...
How to Test The NC (Normally Closed) Terminal of A Relay
The relay's Normally Closed Terminal should read near 0Ω from the NC (Normally Closed) terminal to the COM (common) terminal, when the relay has no...
How to Test The No (Normally Open) Terminal of A Relay
The relay's Normally Open Terminal (in double throw relays) should read a very high impedance(several megohms (MΩ)) from the NO (Normally Open) ter...
How to test if a relay is good?
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. In this article, we will show what resistance readings you should get when you measure various points of a relay. By finding the resistance values, we will be ...
How to check coil resistance?
To check the relay coil's resistance, take the multimeter you have and place it in the ohmmeter (Ω) setting and place the probe leads of the multimeter on the 2 terminals of the relay's coil. It doesn't matter which probe is placed on which terminals. Resistance isn't polarized.
What happens if you read a coil resistance?
If you read a value about the rated coil resistance, the coil works and should function correctly. If you read a very low resistance and very high resistance, the coil is either shorted or is open. In this case, since coils normally are not repaired, you must simply replace the relay.
What is a relay?
Relays are discrete devices (as opposed to integrated circuits) that are used to allow a low power logic signal to control a much higher power circuit. The relay isolates the high power circuit, helping to protect the lower power circuit by providing a small electromagnetic coil for the logic circuit to control.
How many poles does a relay have?
Relays may have one or more poles, indicated in drawings by a single line switch connected to a pin of the relay. Each pole may have a normally open (NO) and or normally closed (NC) contact. The drawings will indicate these contacts as connections with a pin on the relay.
Types of relays
First of all, identify the relay you would like to test; there are three types of relays.
Type 2 Relay test
Step1: The two leads of the multimeter and the coil terminals 85- (C1) & 86- (C2) are connected to the multimeter; if the buzzer rings, your exciter coil is working.
How to test a relay with a multimeter in resistance?
Firstly, Set the multimeter selector dial to Resistance mode. Then connect the Red and Black leads of the multimeter to the coil of the relay.
How to test relay using a multi-meter in diode-test?
If the relay is impaired, put it in a diode test by taking a multimeter and checking across A1 (+) and A2 (-). The meter will apply a small voltage to make the semiconductor, and it will conduct and read that voltage on the screen that will check the (typically NPN) transistor from the base (P) to the emitter.
Conclusion
The relay consists of an “ electromagnetic switch ” for controlling high current devices with a low current circuit. In this article, we describe what a relay is? How many types of relays? What are the main functions and faults of the relay? And how to test a relay with a multimeter.
What is a relay that is normally open?
If the 2 lines are depicted as not connecting at the circle or dot, the relay is a normally open (NO) relay. If the 2 lines are depicted as meeting at the circle or dot, the relay is a normally closed (NC) relay. It is important to know if the relay is NO or NC during further testing.
Where is the relay located?
The relay is typically located in a place where larger electric parts are placed. In a car, this is likely a relay or fuse box. Use your fingers to unplug the relay from the socket in which it is placed. Note the relay position.
What is the diode symbol on a relay?
A relay with internal protection will have a diode symbol shown on the package drawing connected around the control coil. The diode symbol will be a triangle with a line attached perpendicularly to 1 of the points. The line shown on the diode symbol will indicated the positive polarity end of the diode.
Why use a 4 terminal relay?
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. 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. Use these tips to learn how to test a 4 terminal relay.
What happens when a relay is not voltage spike protected?
If the relay has been determined to not be voltage spike protected, the test power source may be connected to the control pins of the relay in either direction. Listen for the click. When power is applied to the control circuit, a slight click should be heard as the relay activates.
