Foglamp Issues

[1984GTTurboVert]

I went to use my foglamps the other day and they didnt work, they worked fine a few weeks ago, and wiggling the wires and toggling the switch some got the indicator to illuminate but not stay lit and i heard the relay clicking but it would only light up the passenger side light.
Crawling under the dash to check whats going on there lead to this.







Pretty bad honestly, not sure how it even worked at all like that.
Since i didnt have anything handy there to actually test voltage i just sprayed down the connections and changed out the switch with one i had to see if anything changed, and nothing worked with the other switch and cleaned terminals. The relay no longer clicks.
Im going back there this weekend with a working voltmeter and checking the wires but i had a few questions beforehand.

1) where is this systems grounds at? The wiring diagram i have shows the wires and where they splice in but not the grounds or the fusible link(i know where thats at).
The fusible link didnt feel to good on the firewall side wire but passed the pull test but im in doubt so im going to change it out anyway. The rusted up stuff under the dash really has me confused since i dont see any leaks around the windshield and the floors are solid.

2) where can i get a new correct switch, relay and fusible link at? Are these even available or am i stuck just buying what will work from the Help! Section at the store?

[emerygt350]

Yikes! good luck, I bet they used the same relay for ages...

[85GTGuy]

Foglight switch:

https://lmr.com/item/LRS-1521486/mus...-86-e2zz-15214

You may want to take a good look at your headlight switch also. Make sure it doesn't have any issues.....

[gt4494]

IMHO the best way to work this is to rewire and put the relay under the hood as close to the battery/lights as possible. This will give you the highest voltage at the light and make them shine better then new. 40ish old wire is just one headache after another. You will never get battery voltage at the lights..

[tbirdman]

Factory fog light relay is D9BZ 14512-A 3 post. Pretty much extinct anymore. NAPA ECH AR235 is a good replacement part and still looks to be available. The relay grounds through the mounting screw. I don't have my EVTM handy, but power from the engine bay comes into the relay, one wire goes to fog light switch and the other goes to the headlight switch (I believe). My fusible link in the harness out to the engine bay went bad so I had to rewire with a new wire from the relay out to the engine bay. I soldered on a replacement fusible link to the end and direct wired it to the starter relay. This was the easiest option since I cant see where the original fusible link was. Fog lights work now. first time in 13 years.

If you don't have one, it's a good idea to pick up an EVTM for your year Mustang. Some good information. I can read it and I'm electrically disinclined.

Also, make sure if you're using the original wiring that you only use the 55 watt H2 bulbs.

[1984GTTurboVert]

Thanks for the replies.
I bought a new switch and the napa relay and just waiting for them to come but im going to go over the wiring, clean the mounting point for the relay and whatnot before i install them.

[1984GTTurboVert]

IMHO the best way to work this is to rewire and put the relay under the hood as close to the battery/lights as possible. This will give you the highest voltage at the light and make them shine better then new. 40ish old wire is just one headache after another. You will never get battery voltage at the lights..

If it werent for trying to keep it original as possible i probably would have redid it like that.