No I have not. I had the connectors replaced and they all work again.

Here is what it's down to. I had my female headlight connectors replaced. My grounds are connected. They worked for a bit then they stopped. My highbeams are working my parking lights work. The only thing that doesn't work are my headlights. I'm currently looking at getting a new headlight switch to see if that is the problem. Is there any way I can test the old one before I buy a new one? I don't want to buy it if I don't need it. Also where can I get these relays from and where do they connect? Are they like the headlight switch?

Thanks for the help SS, Jonathan.

I was afraid this would happen, though I thought the new plugs would melt as well. You will either have to diagnose the whole headlight wiring system or build a new one. If you cannot figure out where to buy relays, then wiring might not be for you.
Relays are switches. Power (+) in, power (+) out, ground (-), and a switchable power on (+). Power in comes from the battery, power out goes to your headlight (low beam or high beam requires separate relays and power), ground goes to ground, and switchable power goes to your headlight switch. For high beams, I dont remember if there is a connection at the headlight switch but you would most likely run that to the multi switch on the steering column. You will require three relays, headligh low beam, headlight high beam, and parking light. You could redo the whole lighting system, including the tailights if you wanted to. It just comes down to how capable you are with wiring and if you have the diagnostic ability and creativity to find and create circuits.
You would get relays from an electronics parts store/supplier, and you dont run the crap they sell at Canadian Tire. You would need high quality Bosch 40-50 amp relays to hold up to the current draw from the lights. Honestly, if I were still in Toronto I'd offer to help but since I'm not I can recommend you to a great shop where I used to do all my work. A friend of mine still works there, and he's just as much of a Mustang junkie as I am. The owner of the shop is also a champ at fixing wiring and diagnosing issues, so it's a very well rounded team especially when it comes to Mustangs! Let me know if you want to have someone take care of this headache for you and I'll pm you the info.
SS

I'm going to try replacing the switch to see if thats the problem. If it isn't then I'll get back to you tonight and you can send me the info for the shop. I'm actually in Oakville, but I travel to Toronto almost every weekend.

Jonathan.

Is it popping the fuse or anything when you turn the lights on. Also pull the light switch out of the dash and see if there is any corrosion or burn marks
Other place to look is behind the rad support for a short in the wire

My fuse is fine. Everyone I have talked to told me it's my fuse. I checked the fuse (OK), I checked the switch (OK). High beams work headlights don't. The only way my high beams work is when I pull the switch to flash them. They don't work when I push the switch to keep them on. Also my fog lights don't work. I turn on the headlight switch on and only the parking lights will come on. I'm taking it to a shop just down the road from where I work. His son was Nick from Nick's Automotive and the mech who will be working on my car specializes in electrical so if he can't fix this problem then I don't know who can. Wish me luck guys. I'll let you all know tomorrow how it goes. Thanks for all you help.

Jonathan.