Shown at the right is the 427SC fan schematic but the ERA GT is similar.
Troubleshooting - Assuming the fans don't
If the fans won't automatically turn on, but work with the dash switch:
If the fans won't work even with the dash switch:
Check Fuse connections - Go to (B).
Check Relay - Go to (C).
|(B) Check that there's at least 12V at both ends of fuse 1. If there
isn't 12V on the right (green or orange wire) side, replace the fuse and
check the wire connections. Some early fuseboxes tended to corrode because
the fuse clamp was riveted to the tab where the wires attached. Later fuse
boxes are one-piece. If the voltage is correct, go to (C).
(C) Disconnect the relay wires and jump the wires that connect to terminals 30 and 87. If the fan works, go to (D) to check the relay and relay connections. If not, the connection from the relay to the fan is defective.
(D) Check that there's 12V at terminals 30 and 85 on the relay/connector. No voltage indicates a bad connection to the fuse box. . Not likely
With all relay connections remaining in place:
(E) Relay Ground
Fan relay plug or wire side of relay
Note! Later 427s use an orange wire from the fuse rather than the green one shown.