I installed a new outdoor circuit. The line comes out of the house and into the LINE side of the GFCI outlet. I connected a wire to the LOAD side and ran it to two standard outlets downstream. My tester says the circuit is wired properly at all the outlets; the tester button appropriately trips the GFCI when used.
Here's the problem: devices plugged directly into the GFCI outlet work fine. However, when I plug the same devices (I tested a light, a fan, and a grounded shop vac) into the downstream outlets, they trip the GFCI.
I'm stumped. Help?