There is a very large class of people that own 65/66 Mustangs that, as far as I can tell, anyway, have been, for the most part, ignored entirely. They don't really want that 100 pt. show car that is so nice and was soooo expensive that they're afraid to drive it, they also don't want to make their car capable of achieving warp factor three. They just want this car that they dearly love to be able to cruise around smoothly and reliably, without having it dump them out on the side of the road or have it start making weird noises or belching out big clouds of funky-smelling smoke. And I think, truth be told, that this is by far the largest class of Mustang owners. They take their car to some technician when what they actually need is a mechanic, and this, frequently, does not work out very well at all for the owner. They don't want to re-engineer the entire car, they just want someone to fix what broke. These are the people that I am trying help out with this blog. Some problems require a little bit of back and forth, as in, "Try this." "I tried that and it didn't change anything."
" Oh. well, you probably need to try that." " I tried that and it helped, but it still isn't quite right." "Now you need to try this...." If you go to http://www.allfordmustangs.com/ and then go to the classics forums, you will be able to do that with a pretty hefty gathering of some very knowledgeable people that also happen to be very friendly. None of that ridiculous one-upmanship, no flaming or abuse, none of that stuff. Just good, solid advice from people that know what they are talking about.

Sunday, September 2, 2012

1965 1966 Mustang Turn signal switch wiring

Once in a very great while it becomes necessary to replace the turn signal switch on a 65/66 Mustang. Once it has been determined that the switch needs to be replaced, you will discover that you have to reuse the old connectors. One is a two-wire connection that will only plug together one way. That connector is for the rear turn signals at the tail lights. If those two new wires are placed into the old connector backwards, what will happen is the right rear turn signal will start flashing when you signal a left turn. Not that big of a deal, and all that you have to do is switch those two wires around and you're all set.
The six-wire connector is sort of a different story, though. The two connectors will only plug into each other one way, but, there are all sorts of wrong ways to place the new wires into the old connector, and, if done wrong, all sorts of disasterous consequences will follow involving smoke, melting wires, etc...

Here is how those six wires are supposed to be installed in the old connector. If you look at the connector from the orientation shown in the picture, you will notice a slot in the cross piece in the center of the connector. Holding the connector so that this cross piece is pointing up and down, and with the slot closer to the top, the wires go as follows, going clock-wise beginning at the top left corner.
1)The top left corner has a yellow wire, which brings power from the headkight switch to the horns.

2)The top right corner has a white wire with a blue stripe, which goes to the front right turn signal indicator.

3)The right-side middle wire is a green/white wire which goes to the front left turn signal indicator.

4)The bottom right wire is blue/yellow, which takes power to the horns.

5)The bottom left is a blue wire, which brings power from the turn signal flasher.
6) The middle left wire is green, which brings power from the brake light switch, so that the brake 
lights are flashing on the appropriate side while the turn signals are flashing.

In the wiring diagram, you will notice what appears to be some extra wires. I drew it like this, oddly enough, for the sake of clarity, so that one can clearly see what each wire is doing. Wires 1 and 8 are both white with a blue stripe. There is actually only one white wire with a blue stripe coming out of the turn signal switch, with the same thing happening with wires 2 and 7, which are green with a white stripe. There is only one green wire with a white stripe coming out of the turn signal switch. If you look at the 6-wire connector that the turn signal switch plugs into, you will see two white/blue wires coming out of the place where the one white/blue wire goes in, with the same thing happening at the place the one green/white wire goes in. Two come out. What the switch itself has is one yellow wire bringing power in for the horns, one green wire bringing power in from the brake light switch, one blue wire bringing power in from the flasher, one blue/yellow wire taking power out to the horns, one white/blue wire taking power out to the right front turn signal and right dash indicator, one green/white wire taking power out to the left front turn signal and left dash indicator, one orange/blue wire taking power to the right rear turn signal and brake light, and one green/orange wire taking power to the left rear turn signal and brake light, with the last two being that two-wire connector. There are some aftermarket turn signal switches with wires that don't really match the colors of the Ford switches. I don't know why anyone would do such a thing unless it had something to do with cheap, but, that was what they did. If you have such a switch, the last two pictures will show you the locations of the wires on a Ford switch. 


JamieBraz said...

Thank you. I appreciate the diagram, have yet to see that on any of the DIY sites I've been researching in order to make this switch.

On Eagle's Wings said...

This was a huge help! And, I stumbled on an answer for the horn power. :) Is this diagram part of your new efforts? I'd love to take a look as I'm rewiring my whole car right now with a Ron Francis kit. The wires they supply are great, but the connectors they supply are worthless for our vintage Mustangs. That means lots of make-shift connections and sometimes confusion between the old and the new. If I had one suggestion right now, it would be to include hints on *where* the grounds connect, instead of just showing the "3-line arrow". Thanks for passing along your knowledge!

Veronica said...

Thanks. I'm happy to hear that this stuff is actually helpful. And, yes, this is one of my new diagrams. The grounds for the rear turn signals don't involve a 'ground wire' per se. The tail light housings ground themselves out on the body of the car. The dash indicators ground themselves out on the instrument cluster, which has a ground wire attached to it by the same screw that holds the instrument cluster voltage regulator onto the back of the instrument cluster, with the other end of that wire attached to the dash support bracket. The front turn signal/parking light assemblies have three wires coming out of them. One is the turn signal, one is the parking light, and the third is the ground.

Bo Edgar said...

Hey Veronica - another one of my issues is covered here; my turn signals are backwards. When I push up, the left signal goes on and when I push down the right one goes on. I see that I just have to switch the wires in the two connector plug. My question? How do you remove the wires from the plug and then get them back in?

Veronica said...

If you look at the 2014 posts, you will see one titled 'turn signal switch tool'. You just push that onto the wire, wiggle it around a little, and then pull the wire out of the backside of the connector. When you're putting the wires back in until you feel a little click. Nothing to it.

Bo Edgar said...

Hey Veronica - finally got back to the car this weekend and got the rear turn signals working correctly. Thanks for the tip. I have one issue left involving turn signals. My left front turn signal is not flashing. The parking light works, but not the turn signal. I've changed the bulb - even tried it on the side that worked and the bulb is good. I even changed out the turn signal switch and that didn't help. Anything else I should try?

Veronica said...

I think that the first thing I would try would be check the wire at the connector that the parking light assembly plugs into for power when the turn signal is supposed to working. If it is getting power, then you socket assembly either needs to cleaned of corrosion in there where the bulb plugs into it, or, if that doesn't work, you need to replace the front parking light assembly. If it is not getting power, then you need to trace the wire back until you find the break. At the six wire connector in the main harness that the turn signal switch plugs into, you will see one spot that has two green/white wires coming out of it. One of them is the dash front turn signal indicator light, and the other is the front left turn signal. If power is leaving the connector like it's supposed to be, but not making it all the way out to the socket, then you have an oopsie in the wiring somewhere in between. Let me know what you find out.

Diggler said...

Specs... 1965 Coupe 289 with lamps.

So I have been doing a lot of work on my car the past 6 weeks and I have a wiring haywire somewhere. First off, the car starts fine, runs fine, lights work, brights work, tail lights work, reverse lights work, parking lamps work, horn works. I have added the following new parts.

New tail light kit (housing, bulbs, chrome, etc.)
New backup lamp kit
New parking lamp kit
New main wiring harness from Mr. Mustang; the main headlight switch wiring harness (voltage reg, lights, park lights, horns, alternator, solenoid)
New main wiring harness for the engine (temp sending unit, oil sending unit, two speed fan, ignition, coil, etc.)
New Autolite Voltage Regulator
Rebuilt the fuse box with shiny new connectors and fuses.
New alternator wiring harness to match original that plugs in to the headlight wiring harness and attaches to the positive side of solenoid
New starter
New Scott Drake constant voltage regulator on the back of the inst panel.
New flexplate (flywheel)
New neutral safety switch

Battery has been fully charged at the local Autozone
Alternator passes the test (twice) done at Autozone

So here is/are the issue(s)

1. The ALT lamp stays on constantly. There is no sign of battery drain as I can drive around town, stop, start again, leave it for 4 days and go out and start it again.

2. When I switch the key to the "On" position, the left turn signal works fine. When I put the right turn signal on, both rear taillights flash as if it were using hazard lights (which I don't have).

3. When I switch the key in the "On" position and turn on the parking lamps, the left turn signal works fine. When I turn on the right turn signal. The turn signal light comes on and stays lit. The right tail light and park lamp come on as if it wants to flash, but it stays bright. At the same time, the left tail lamp dims just a bit but still stays lit because it's in the parking lamp position.

4 When I switch the key in the "On" position and turn on the lights, the same thing happens as explained in #3

***Here is where it starts getting weird***

5. If I leave the key in the off position and not even have it in the ignition, nothing happens left or right, obviously

6. If I leave the key in the off position and not even have it in the ignition, and turn the parking lamps on and then the left turn signal, nothing happens except the left tail light dims a bit. But if I turn on the right turn signal, the left rear tail light dims a bit and then the oil light comes on (yeah.. head scratcher). And to make that more weird, if the fan is in the low or high position, it will make the oil light blink and the heater fan start pulsating in the same rhythm as the turn signal noise.

7. The same thing happens as it did in #6 if I leave it in the off position, not have the key in it, turn the lights all the way on. The left tail lamp will dim a bit and the oil lamp will come on. And if the heater is on, it will make the oil light and heater fan blink/turn on in unison with the turn signal flasher.

Obviously there is a wiring mix up here, but I can't seem to find it. I am decently skilled when it comes to working on this car because it's so mechanical and the wiring is pretty basic, but this has stumped me. Does anyone have any ideas of where to start with this? I have a feeling that once the culprit is found, the ALT light will go off, the oil light will stop flashing and all will be back to normal. That's how it seems to go with this car.

Again, starts fine, drives fine, but this issue is weird and confusing. All of the fuses in the newly rebuilt fuse block are still good, but maybe I shouldn't rule out a mis-wire at the fuse block. But if that were the case, I would think there would be much bigger and noticeable issues.

I have not replaced the turn signal 2 prong plug because I have never had an issue before this. So that is not new.

Veronica said...

These old cars sure are fun. :)You probably have several little things that are accumulating into all sorts of weirdness. I think that the first things that I would do is to make sure that the ground wire that goes from the screw holding the instrument cluster voltage regulator onto the back of the instrument cluster to the dash bracing back behind the instrument cluster was making good contact at both ends, and, I run a ground wire, for test purposes only, from one of the studs sticking out of the back of the tail light housings to a good ground somewhere, just to make sure that they were grounded well enough. Do one for each tail light housing. After you get that set up on the instrument cluster and the tail lights, run through that same series of tests that you did previously to catalog what was going goofy under what conditions, and see if anything changed. Let me know what you find out.

Diggler said...

After replaying everything in my head and knowing that it had to be the alternator, I replaced the alternator and got a new battery on warranty. Turns out, that didn't work.

So on a hunch, I put back on my old dingy-looking voltage regulator and took off the brand new Autolite one that I bought from CJ's and the ALT light magically went out.

As far as the tail lights are concerned, the 50 year old connector was sort of shot. You have to have it in a specific position for it all to work properly, so I bought a tail light wiring harness and will install that when it gets here.

It runs great now and it goes to show you that in terms of the voltage regulator, dingy-gross looking can beat a shiny new one. Glad I kept it!

Veronica said...

That seems to be a pretty common failing with the new voltage regulators that made as a 'concours' reproduction. The BWD voltage regulator with the part number R-295 seems to be the most reliable new one. It used to be, at least. I haven't bought one of those for a while, so, they could be about the same level of quality as the new one that you just bought. You can get them at any major auto parts chain store, for something in the $30 range.

A new tail light harness certainly won't hurt anything, and should fix at least some of the weirdness back there.

Brad Robison said...


I have an issue that I need help with. I have a 66 and have been restoring it for a few months now. I'm just about done, but I'm having an issue with the turn signals. I installed some led parking lamps/turn signals in the front and led tails in the rear. I also installed an electronic flasher for the new leds. Everything works great until I turn the car on. The flashers work for about 3-5 flashes and then either stay on or turn off all together. The issue only happens with the car on. I've tried multiple flashers too with no luck. Any ideas?

Rhett Holyoak said...

So I broke down and bought a painless wire harness to see if I could solve some of these "Weird" issues. When I finished with the harness the turn signals would not work properly. The running lights work fine as well do the brake lights. If I just have the running lights on (Brake NOT applied) and move the turn lever to the left or right nothing happens. If I apply the brake and move the turn lever either right or left that brake light goes out (or returns to what should be just the running light).
They don't flash and they don't light up on the instrument cluster either.
So as I have heard someone say before "These old cars are fun!" So in driving I have just waited until I needed to turn, applied the brake and then while the brake is on I move the turn lever up and down manually, of course timing it just right so anybody behind me thinks I have working blinkers! I know, its fun. You should try it sometime, it really livens up the drive.
Anyway, on the turn signal wire diagram, the colors are opposite that of what the painless wire harness is. In fact I spent some time trying to connect the harness only to finally realize that I was just lining up wires and not the actual connector body. Painless insists that their end is wired correctly. I have double checked my wiring on the turn signal switch side and it is also correct. Do these things need to be grounded on anything behind the steering wheel to work properly?

Veronica said...

Personally, I've never been a big fan of handing someone a few spools of wire and a box full of butt splice connectors and calling that an application-specific kit, but, that's just me, I guess. It sounds like there is no power reaching the turn signal flasher. How that is supposed to work is that keyed power goes to the flasher, and, from the flasher, on into the turn signal switch by way of that blue wire in the 6 wire connector. That's where I would start looking. let me know what you find.