The relay must be on the ground side of the load when the voltages above the coil are hot. The case should be grounded. The relay can be on either side of the load for hot switch voltages that are lower than the coil.

What happens if a relay is not grounded?

One wire that comes out of the relay box is the ground wire. ... If it is, the wire will not make a solid contact with the metal, and it would be as if you did not have a ground wire attached.

What is grounding on a relay?

The second pin, or ground is the housing which must be mounted direct to chassis or otherwise grounded. If your relay is in a plastic housing it will have 2 pins for the coil, usually reversible.