Time for another major upgrade.
The wiring harness mostly being assembled by Ford it has the same issue Ford (really everyone at the time) had with the full load of the headlamps routing form the battery, up to the dash, through the headlamp switch and back to the front of the car. Long runs meant voltage drop and that style of wiring was prone to overheating and burning up the headlamp switch and it's associated plug. I talked about this back on page 20 (gee, this thread is long...)
I had to go in and replace the switch in 2020 because the terminal had failed and roasted the switch and the main battery terminal but during the summer my headlamps started to fail again when the high-beams were on. Finally over the weekend I could smell hot plastic and the low beams would flicker out so it was time to go back in and see what failed, plus make a change.
Harness conversion kits are available that relocate the load of the headlights to a pair of relays in the engine compartment, leaving a few hundred mA going through the switch instead of many amps. You simply plug them in to an old headlamp socket, attach a battery link and grounds and you are set. They're also extremely cheap.
Usually you can get away with the packaged wire lengths as everything is nicely crimped and sleeved but the Eagle has a problem in that between the positive post and the front of the car is the battery. Either you mount the relays in the engine compartment and your headlamp wiring is too short or you locate the relays in front of the battery and extend its battery wire an extra 12 inches. I opted for the latter.
While not ideal because a relay issue means pulling the headlamp assembly apart, behind the headlamp bucket is a cavity which will fit a pair of relays with room to spare. I located it as high up as I could to keep water out of the sockets and then routed the battery cable through the adjacent hole, around the battery tray and up to the battery terminal on the starter solenoid. Each lamp socket gets a new ground cable which terminates at a new point on the body. Yes I ground down under the terminals to ensure a good contact. The harness tucks away cleanly in the cable path of the old headlight harness which I left in place but tied back. The white cable clamp below the relays supports the harness so it cannot unplug from the relays.
Then came testing. The new harness plugs into the 3-terminal socket of the old low-beam lamp. For some reason all three wires were incorrect so the socket had to be de-pinned and reconfigured.