一、Testing methods of automobile relay:

1. Open circuit detection

Multimeter resistance measurement method can be used to check and judge whether the relay is good or bad.The multimeter R x 100 Ω archives check (85) and (86) (87), and the feet should be conduction (87 a).The resistance between (87) and (30) feet should be infinity.If the results are inconsistent with the above rules, there is something wrong with the relay.

2. Power-on test

If there is no problem with the above inspection, add 12V power supply between (85) and (86) feet, and use the multimeter to check that (87) feet and (30) feet should be switched on.If it does not conform to the above rules, or the relay heats up after energizing, it means that it has been damaged.

二、Phenomenon and reason of relay heating:

1. Abnormal heating occurs in the center of the contact, and the contact is fusing, melting, dissolving and solidifying, with poor action.That is because the contact repeated switch caused by the continuous occurrence of open and closed arcs;

2. The circuit inside the relay is fusible and the contact is dissolved and solidified, and the action is not good.This is most likely due to abnormal overcurrent in excess of the contact rated current;

3. Local short circuit of the coil causes fuse failure, and the coil breaks, leaving traces of abnormal heat in the coil.It could be an overvoltage applied to the coil;

Solutions to the above phenomena are as follows:

1. The voltage of the relay with AC specification shall not be lower than 90% of the rated voltage;The voltage of the relay of DC specification shall not be lower than 79% of the rated voltage;Avoid high frequency switching;

2. Conduct safety design on the circuit to prevent the rated current over the contact from flowing through the contact circuit;

3. Do not apply a voltage above the rated voltage on the coil.

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