testing relays
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
Likes: 1,678
From: Stephensville WI
Okay, sorry...just another Monday!!
Fleet Mechanic
Joined: Apr 2007
Posts: 1,433
Likes: 7
From: NH
Testing a relay is pretty simple.
I am guessing it is of the standard automotive "cube" relay. First, most relays have a diagram on its housing. Most of these you may need a magnifier to read. There are generally 2 terminals isolated from the other terminals. These 2 terminals are for the coil (12V) Typically these are not polarity sensitive but some have an internal diode (or LED for status) that is used for noise immunity and/or nusance tripping. The diagram on the relay should denote a diode or not. If not then the +/- wires can go on either terminal. Once the 12V is connected you should hear or feel the coil activate. Remove the 12V power. You will nead a ohm meter or continuity tester (you can make one from a simple battery and light if need be). If the diagram exists on the case it would be helpfull for you to redraw the diagram on paper if possible. Many relays will have a 3 pole configuration, meaning 3 sets of contacts for each pole so 9 terminals total (not including the 2 for the coil). A common terminal, a normally open contact (N.O.) and a normally closed contact (N.C.). Many relays are manufactured with their case the same but may eliminate some of the poles. Your relay may only be a single pole (3 contacts) or a double pole (6 contacts etc..). They can also have only 2 terminals per group meaning it is a single pole single throw (spst)
Typically the common terminal is the center terminal within its group. The remaining contacts will give you continuity either N.C or N.O.. The state of each contact will reverse when you put power to the coil. I know it all may seem a little confusing but after you get familiar with them their pretty easy to understand. Good luck
Dave
.
I am guessing it is of the standard automotive "cube" relay. First, most relays have a diagram on its housing. Most of these you may need a magnifier to read. There are generally 2 terminals isolated from the other terminals. These 2 terminals are for the coil (12V) Typically these are not polarity sensitive but some have an internal diode (or LED for status) that is used for noise immunity and/or nusance tripping. The diagram on the relay should denote a diode or not. If not then the +/- wires can go on either terminal. Once the 12V is connected you should hear or feel the coil activate. Remove the 12V power. You will nead a ohm meter or continuity tester (you can make one from a simple battery and light if need be). If the diagram exists on the case it would be helpfull for you to redraw the diagram on paper if possible. Many relays will have a 3 pole configuration, meaning 3 sets of contacts for each pole so 9 terminals total (not including the 2 for the coil). A common terminal, a normally open contact (N.O.) and a normally closed contact (N.C.). Many relays are manufactured with their case the same but may eliminate some of the poles. Your relay may only be a single pole (3 contacts) or a double pole (6 contacts etc..). They can also have only 2 terminals per group meaning it is a single pole single throw (spst)
Typically the common terminal is the center terminal within its group. The remaining contacts will give you continuity either N.C or N.O.. The state of each contact will reverse when you put power to the coil. I know it all may seem a little confusing but after you get familiar with them their pretty easy to understand. Good luck
Dave
.
