Lighting/Wiring issues

[jmsrx]

So I will try to give as much detail as I can regarding the issue. Sorry for the long post.
I did not build this coupe. It is the 2018 SEMA coupe which I purchased earlier this year with about 1000 miles on it. The first time I noticed the issue was going to a coffee and cars event early in the morning. It was not light outside, so I had the headlights on. After driving for about 10 minutes, I noticed that the lights started flashing on and off intermittently. Since then I have found that it happens every time I use the lights about 10 minutes into the drive.
So the first thing I did was check the switch. I noticed it was getting very warm. I pulled it out and noticed some melting on the plastic casing. I purchased a replacement and installed it. The issue did not go away but the new switch does not seem to be getting as warm yet. These switches do have a cutoff built in correct? Just thought that might be important. I then started doing some situational testing. We know it happens when I drive the car with the lights on. I found that it only affects the headlights and fog lights. The gauge lights and parking lights do not flash. They are on a different circuit. If I drive the car without the lights on then park it, leave it running, and turn the lights on it will happen within about 5 minutes. If I drive the car, park it, turn it off but turn the lights on it will happen in about 10-15 minutes. Once it starts I can either unplug the headlights or the fog lights and it will stop for about 15 seconds then start again. If I do not drive the car at all but turn on the lights it does not happen, at least not within an hour period I have tested it for. So it seems to have something to do with a hot vehicle not necessarily a running vehicle.
I have very rudimentary electrical testing skills. I have an inexpensive digital voltmeter but do not have an amperage tester. Any thoughts on where to test next? One person has told me to find the ground to the frame and make sure an electrical star washer was placed on that connection. I have not done that yet.
Thank you in advance for any help.
James

[UpNorth]

Hi James,
I am by no mean an electrical guy, far from that I tell you.
Hopefully the pros will chime in a little later.
But from my ignorant stand point could it be possible that the lights are on a same circuit as the radiator fan?
Just my 2 cents.

[AC Bill]

I would hope the headlights are run through a relay? Wired correctly a relay should prevent the switch from ever getting hot. If not, there could have been some additional overheating issues elsewhere in the circuit, perhaps causing a short. As the circuit warms up, it may expand so contact is lost, then cools, and contact is regained. It may not be enough to trigger the fuse, which would probably be a 20 amp.
The first thing I would do is check that the grounds are all solid, inspect the bulb sockets, and any connectors, for signs of overheating. If all looks good, I would replace the headlight relay, or install one if there isn't one. Some donor built cars had daytime running lights, and the relay for them also acted as the headlight relay.
It almost sounds like engine heat is playing a roll. Perhaps some wiring is a little close to the headers?