Table of Contents
How do you read a relay?
Relays are switches that open and close circuits electromechanically or electronically. Relays control one electrical circuit by opening and closing contacts in another circuit. As relay diagrams show, when a relay contact is normally open (NO), there is an open contact when the relay is not energized.
What do the numbers mean 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.
How do you read a relay specs?
Understand Relay Specifications to Get the Most Out of Your Switching System Life Expectancy. Maximum Switching Volts. Cold Switching Voltage. Switch Current. Carry Current. Pulsed Carry Current. Power Rating. Minimum Switching Voltage.
How are relays labeled?
Although most relays are labeled at the bottom, you can always find the 30 pin set perpendicular to pins 87 and 87a for easy identification to the power source. Realizing that 85 and 86 are the coil pins, these pins will be transferring the current through the coil.
How a relay works 12v?
Relays install between the power source and the electrical accessory requiring on/off power. When the relay is energized, the high current to operate the accessory flows from the power source, through the relay, and directly to the part.
What happens if you put a relay in backwards?
Often seen as a quick fix, using the wrong relay for the application can cause inadvertent voltage spikes. Many relays, if installed for the wrong application, could and will cause a short (Internal Relay Circuit) and most likely cause functionality issues or even damage to the vehicle computer systems.
What does 87a mean on a relay?
87a. High current (load) Output to other device, normally closed, pulled open when coil is energized.
What does full ISO relay mean?
An ISO relay is one which adheres to a standard pattern for its electrical terminals that has been spelled out by the International Standards Organization. ISO-style relays also generally plug into their end application via sockets.
How do you read a voltage relay?
Measure the voltage across the relay where the 110-volt AC current enters and exits the relay. A reading of zero volts would mean the contacts are working. High volts for this reading would show that the contacts are damaged or burned. Replace the relay if this is the case.
How much voltage does a relay need?
Most are rated at 12v, usually a range of 12-15v. Actual voltage required to operate the relay is usually a little under 12v. That is why your accessories can still operate with the key on and engine off, usually making actual voltage a bit under 12v with lights on.
How much voltage can a relay handle?
Relay operating voltage is 24 v d c.,relay contacts can carry up to 10 amps. relay coil current would be one amp. Relay operating voltage is 24 v d c., but contacts carrying capability suppose 200 amp.,in this condition,contacts closing pressure must be such that 200 amps flowing the voltage drop must not exceed 5 m v.
How many pins does a relay have?
A normally closed relay will switch power OFF for a circuit when the coil is activated. 5 pin relays provide 2 pins (85 & 86) to control the coil and 3 pins (30, 87 & 87A) which switch power between two circuits. They have both normally open and normally closed connection pins.
What does the designation 31 represent on a wiring diagram?
For exam- ple, a terminal 31 designation always refers to a direct connection to vehicle ground and a terminal 30 designation always represents a direct connection to the battery positive terminal.
Does polarity matter on a relay?
Actually, unless the relay has a diode in it, it won’t matter if the polarity is switched; the electromagnet will be energized regardless. When you touch 86 and 85 to the battery, the electromagnet pulls the switch contacts together, so the resistance between 30 and 87 should read essentially zero (under one ohm).
How many amps does a 12v relay 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.
How do you operate a relay?
How relays work The input circuit (blue loop) is switched off and no current flows through it until something (either a sensor or a switch closing) turns it on. When a small current flows in the input circuit, it activates the electromagnet (shown here as a dark blue coil), which produces a magnetic field all around it.
How do you tell if a relay is bad with a multimeter?
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).
Can you put a relay in upside down?
Hg-displacement relays will stay closed if you flip them upside down, because they are filled with liquid.
