I have a Fused Service Switch (lever type) and Load Center (breakers) mounted directly beside each other. The load center is physically attached to the service switch with 1.75" conduit.

The two 'hots' and neutral from the switch run through this short 3" conduit into the load center but there is no ground wire between the two boxes.

Does the ground rely on the conduit between the switch and the load center?

Can I connect the two boxes together with a heavy ground wire or bonding strap?

Thanks John

Good Idea. It will make sure disconnect remains grounded.