Headlights

^^Start at the dimmer switch. That is easy to access and "splits the problem in the middle. Turn on the HL switch and probe the dimmer with a meter or test lamp. Two of the terminals are hot, when you flip the dimmer, the third one comes hot and one of the other two goes cold. That is two are always hot with the HL switch on

Work the dimmer and see if the high beam indicator comes on and off. If it does, the problem is likely out front in the harness, connectors, ground.

The HL switch has TWO power sources. One source is ONLY headlights and is not fused

The second source operates tail and park and the dimmer controlled dash lights

From the HL switch, power goes to the dimmer, which feeds off either high or low, through the bulkhead connector, and out to the harness in the engine bay

Make certain the bulkhead connector is firmly assembled, and check the ground connection out on the radiator support. BOTH headlights ground at ONE wire connection to the rad. support