Unplug any relay terminal wiring with the interior car A/C controls in the “off” position. Check all three wires with the test light; with the engine running, the wires should all be inactive. With the engine running, turn the A/C control or switch to “on” at the dashboard. Check the three wires again.
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.
Close the S1 switch and the relay should put 110 volts of AC current on the light bulb, causing the light bulb to turn on. Test the light bulb for the presence of 110 volts AC with the meter. Replace the light bulb if voltage is present and the light bulb is not lit; it may indicate a bad relay.
In fact, the life of a relay is essentially determined by the life of its contacts. Degradation of contacts is caused from high in-rush currents, high- sustained currents, and from high voltage spikes. … Relays can also fail due to poor contact alignment and open coils.
Why is protection relay testing important? Due to the critical nature of protection relays, testing during the commissioning stage is crucial for confidence in the operational safety of an electrical system. Additionally, testing on a regular basis is necessary to ensure correct operation is maintained.
The Shake and Rattle Test
Unplug the start relay from the compressor and give it a shake. If you can hear rattling on the inside of the start relay, then the part is bad and will have to be replaced. If it’s not rattling and appears to be in good condition, you may have a problem with the actual compressor.
Possible causes are low refrigerant, a faulty pressure switch, a faulty control switch or a faulty computer. If power and ground are found here, move to the next step. With the engine running, and the A/C controls in the max cooling positions, test for power at the compressor clutch electrical connector.
You can use your car’s owner’s manual to help locate the fuse. If the new fuse blows once it’s been replaced there is a short in the system. This relay supplies main power to the compressor via the system fuse. Locate the relay in the fuse panel or power distribution center using the owners manual.
If your starter relay has gone bad, the electrical signal will never make it from the battery to the starter motor. As a result, your engine won’t turn over – no matter how many times you turn the key. A faulty relay often produces an audible clicking sound when you turn your car.
At the compressor’s front side, unplug the single wire connector, take a jumper wire and attach it to the wire that you just disconnected from the compressor. Connect the other end of the jumper’s wire to the positive terminal of the car battery. This will enable the compressor to start manually.
One of the reasons why compressors do not engage is because of a low pressure lockout, a poor ground, a bad clutch coil, an opening in the wire to the clutch coil, or simply a blown fuse. There are several ways A/C compressor clutches receive power.
Unplug the switch and use a test light to make sure that you have power to one of the wires. As long as you have power jumo the two wires together with a paperclip and this will activate the compressor clutch for you.
The relays are usually supplied with 12 V directly from the vehicle battery. 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.
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.
12V DC relay switches are the best solution for full voltage applications, as they allow a low current flow circuit to control a high current flow circuit, like a vehicle’s horn, headlights, auxiliary lamps, fan motors, blower motors and countless pieces of equipment existing on vehicles today.
Press and hold the Power and Volume buttons at the same time. … Once you hear “Continue holding the buttons to Factory Reset the device…” and feel the Relay vibrate, you may release the buttons!
The relay operates only when the V/I ratio falls below a predetermined value (or set value). During a fault on the transmission line the fault current increases and the voltage at the fault point decreases.
Switching an inductive load. The biggest “enemy” of a common relay is an inductive load, such as a solenoid or an electromagnet. Its behavior is the most damaging, capable of completely destroying (welding or burning) the relay contacts.
Acceptance testing ensures that the relay is not damaged. Commissioning confirms that the relay’s protective element and logic settings are appropriate to the application and will operate correctly. Acceptance tests are generic and commissioning is site specific.
The standards that cover majority of relay performance aspects are IEC 60255 and IEEE C37. 90.
Use a high impedance test light to test that the relay is receiving power. Connect the alligator clip from the light to a suitable ground. Probe the wire from the relay to the component it controls. If the bulb lights, then there is power leaving the relay, and it is working properly.
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