How to Test a Relay
Consult the relay schematic or data sheet., Do a basic visual inspection of the relay., Disconnect the power source.
Step-by-Step Guide
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Step 1: Consult the relay schematic or data sheet.
Relays have fairly standard pin configurations, but it is best to search for the data sheets to find out more about the number of pins from the manufacturer, if available.
Typically, these will be printed on the relay.Information on current and voltage ratings, pin configurations, and other information is sometimes available in the datasheets will be invaluable in testing, and eliminate most errors associated with testing.
Testing pins randomly without knowing the pin configuration is possible, but if the relay is damaged, results may be unpredictable.
Some relays, depending on their size, may also have this information printed directly on the body of the relay as well. -
Step 2: Do a basic visual inspection of the relay.
Many relays have a clear plastic shell containing the coil and contacts.
Visible damage (melting, blackening, etc) will help narrow down the issue.
Most modern relays have an LED to tell you if they are in the active state (ON).
If that light is off and you've got control voltage to the relay or coil terminals (typically A1and A2 ) then you can safely assume that relay is bad. , Any electrical work should be done with all power sources disconnected, including batteries and line voltage.
Be especially mindful of capacitors in the circuit, as they can hold a charge for a considerable length of time after removing the power source.
Do not short capacitor terminals to discharge.
It is best to check your local laws before performing any electrical work, and if you feel unsafe, leave it to the professionals.
Extra low voltage work typically will not fall under this requirement, but it's still important to be safe. -
Step 3: Disconnect the power source.
Detailed Guide
Relays have fairly standard pin configurations, but it is best to search for the data sheets to find out more about the number of pins from the manufacturer, if available.
Typically, these will be printed on the relay.Information on current and voltage ratings, pin configurations, and other information is sometimes available in the datasheets will be invaluable in testing, and eliminate most errors associated with testing.
Testing pins randomly without knowing the pin configuration is possible, but if the relay is damaged, results may be unpredictable.
Some relays, depending on their size, may also have this information printed directly on the body of the relay as well.
Many relays have a clear plastic shell containing the coil and contacts.
Visible damage (melting, blackening, etc) will help narrow down the issue.
Most modern relays have an LED to tell you if they are in the active state (ON).
If that light is off and you've got control voltage to the relay or coil terminals (typically A1and A2 ) then you can safely assume that relay is bad. , Any electrical work should be done with all power sources disconnected, including batteries and line voltage.
Be especially mindful of capacitors in the circuit, as they can hold a charge for a considerable length of time after removing the power source.
Do not short capacitor terminals to discharge.
It is best to check your local laws before performing any electrical work, and if you feel unsafe, leave it to the professionals.
Extra low voltage work typically will not fall under this requirement, but it's still important to be safe.
About the Author
Jean Chapman
Brings years of experience writing about cooking and related subjects.
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