Hi Darrel,
First I have to say "your welcome", glad to assist. 2+2GT has provided you with thee Ford Illustration. Good 2+2GT, very helpful.
Darrel you have written a very detailed report. What I have determined is this.
1. You have a 2 speed windshield wiper switch. But do you know if you have a single or two speed windshield wiper motor? That's because you described the "7 terminal" lugs on the back, (which is for a two speed). One speed has only 5 terminal lugs. But you are missing the extra color coded wires for the 2 speed motor and the washer motor, and yes their is a ground wire on it.
2. You have 4 wires: BL, OR/BLK, BLK, WH, and of course you are missing the O/W wire, (which is used on the single and the 2 speed switches). No wonder you're are having a tough time.
Yes, you could be right, the O/W wire could have been cut, but it originates from the ignition switch and can be found somewhere in the harness, unless it has been totally removed or carelessly or precariously slashed/pulled off. Be sure to determine this.
3. Were the wipers working anytime you have had your new Stang?
4. Do you have a windshield washer/pump motor, located on the driver side inner fender side wall? It should be a BLACK wire on the pump if you have one. If it is there it would connect up to your "7 lug terminal at the back of your 2 speed windshield wiper switch.
5. What do you think, someone might have put a two speed switch in and removed/severed the O/W wire from the ignition? Received the power from the fuse box somewhere, assuming that your windshield wipers were operating before your new wiring installation? Added a washer pump, but could make it work because they realized they need to connect extra wires to the 2 speed switch?
6. The "purple" wire would go to the fuse, that's the way the new wiring harnesses install now.
7. I'm thinking that if in fact the original wiring is for a single speed windshield wiper motor and the washer/motor pump was added later along with a 2 speed windshield motor switch, then, you can still use your 2 speed switch and your Ron Francis "PURPLE" wire would go to the top terminal, (replacing the missing O/W wire which you won't need any more. HOWEVER, maker sure that there isn't a O/W wire copper exposed anywhere! Look at the ignition switch because that's where it connected from that end to the wiper switch.
8. Also, you would only need one wire directly from the washer motor to one of the other terminalswithout wiring from the washer motor to the switch it won't work. But check out the above first before addressing the washer motor.
Check this out, but this is how I think it goes:
Top to bottom of switch going down as you described with your original wiring/terminal lugs. Are there letter markings, i.e., a,b,c,d,e,f,g, on the back of the switch for each lug? I don't have a pic of the back side of the switch. If the back doesn't have a "lettering" for each terminal, you'll have to describe it to me, scan a hand drawing of the shape of the switch what color wire goes where, etc., or if you have the switch out, take a pic and post it. I have a lot of time on my hands to assist you. Your almost there if you haven't figured it on your own already.
Back of wiper switch
fuse box-----PURPLE------------- A
wiper motor------BLUE---------------B
wiper motor "ON"-----O/BLK------C
wiper motor "PARK"---BLACK------D
wiper motor GROUND-WHITE------E
Although I believe I have the correct wires colors to functions, I am not so sure about the lettering terminal lug designations. So think it through before making the connections, okay?
WIPER MOTOR: Does this wiring scheme hookup look like what you have? BL
BLK
O/BLK
Let me know what you think, if this helps. It's late for me, so I'm going to get some rest and check back tomorrow.
cheers, Tony