1968 Continental Headlight Issues

Bill:
I appreciated your input on my prior questions regarding only being able to start the car with a shot of carb cleaner, the alternator light staying on, and the wiper blade orientation. I have since rectified these problems the rough start was a matter of cleaning the carb, the alternator light was by installing new alternator, and the blades were a matter of switching positions and getting new blade inserts. In any event my latest problem is hi beam cuts out after driving the car for 10+ minutes at night. Once the car has been running for at least 10 minutes and if I switch on the hi beams both hi and low beams stay on for 10-15 second and then they either flicker or turn completely off. If I I tap the foot switch to put lights back to the low beam everything is fine and when I switch back to hi beams it takes 10-15 seconds for the problem reoccur. The hi beam indicator light in the dash also flickers and or goes out. The car is “not” equipped with the auto headlight dimmer so in looking over the schematic I have eliminated the photo eye and amplifier unit in my search for the answer. Also as near as I can tell the floor mounted high/low foot switch is in good operation because it makes a clear on/off for the high beams. Therefore, I think it is either a bad ground somewhere or the headlamp dimmer power relay once the car gets warm and the relay heats up.
I am leaning more towards the relay especially since I’ve noted the 10-15 seconds it takes to have the problem occur. Also in the wiring schematic the wire colors are marked 498, 499, & 501 for the 3 prong part of the relay going to the 13A018 Assy. and 500 & 502 on the 2 prong part of the relay going to the headlamp dimmer switch. The problem is the schematic does not have a color key code for these # wires. I have attached a copy of the schematic for reference. So I’m looking for your opinion on the problem and to see if you know where the headlamp dimmer power relay is located on the car?
Sincerely,
Joe Pepe, Jr.
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Greetings Joe –
This is a common issue with many older vehicles. Firstly, if your Lincoln does NOT have the automatic headlamp dimmer option as you state the circuit will NOT have the power relay. If you have the original style sealed beams installed and not some high power draw beams this issue is usually caused by a fatigued circuit breaker within the headlamp switch. In this case the switch would need to be replaced. You can diagnose this by testing the power feed at the foot dimmer sw. with the headlights activated in the hi beam position. Using a 12 v test light monitor the power feed wire at the foot dimmer switch from the headlamp sw. If the power to this wire and the headlamps is lost after the 10-15 minute time period, the headlamp switch will need to be replaced or if you have super hi draw beams, relays will need to be installed in order to unload the circuit breaker in the switch. A secondary possible cause is a poor connection at the headlamp sw. plug that you can easily see from a melted plug contact at the switch. The over heated plug contact will transfer to the breaker inside the sw. and cause it to open the circuit. The wire color that you will need to test at the foot dimmer switch should be RED with a YELLOW stripe. In any case we will have the parts necessary for you to correct the problem. Good luck with the diagnosis and let us know what you find.
Sincerely,
Bill