How Do I Correctly Test a Relay

[philipk65]

I have a relay I need to check. You're suppose to test the power terminals. Are they the larger 2 terminals? I get a reading of 0 with the two larger contacts and a reading of 002 with the two smaller terminals Is this relay good? Thanks! Kevin

[discnik]

Which relay are you trying to test.

I like to test relays live. I use 6" pieces of wire with the correct terminals on each end and remote the relay. Find the wiring diagram that pertains to that relay. Find out which terminal is the input hot port, either all the time hot or in run. Look at the diagram and determine where the voltage is supposed to go and find out if it does. If you can see which wires, color codes, go to which terminals, this helps.

[old_master]

Usually the terminals are numbered on the side of the relay. If so, the resistance readings at rest should be as follows: 30 to 87 = infinite. 30 to 87a = less than 5 ohms. 85 to 86 = less than 5 ohms. When ground is applied to 85 and battery voltage to 86, 30 to 87 should be less than 5 ohms. Hope this helps

[philipk65]

This is an A/C relay. I don't see any numbers on the sides. On the top of the relay there is a 6 digit number and underneath that is a 3 digit number.

[old_master]

Are there 4 terminals or 5? What year and make is the vehicle?

[philipk65]

Old_Master, There are 4 terminals (2 larger, 2 smaller) on my '91 Chevy S-10 4.3L