Other end of backup switch connection point

[dcmarsh]

In the process of cleaning up my 71 +2S I’ve owned since the ‘70’s and now have retirement time to work on. The reverse lights don’t work and I’ve discovered that the wire from the transmission is disconnected. I’ve tested it and it does provide continuity when in reverse. It is long enough to go into the engine compartment, but I don’t see any corresponding plug on the engine compartment loom. I also don’t see a point where it would go towards the rear of the car. Any hints would be most appreciated.

Thanks!

Dave

[stugilmour]

Welcome back to your Plus 2 Dave.

I am only going by memory and a reference to the Federal wiring diagram in the WSM. Often the Federal diagram can be helpful to locate stuff as the diagram is sort of a layout diagram rather than a pure schematic.

Anyway, it looks like the Green/Brown and Green wire pair from the transmission mounted switch join the main engine loom around several wires running to the voltage regulator on the firewall. If you have access to the Federal diagram the wire colours are called up as 35 and 3 respectively. The diagram does not show a bullet connector though; I seem to recall one though. My loom is now non-stock so not sure.

Green (Hot in Run & Start - Fused) supplies power from one of the two common fuses; your car will be different in this respect as you have more fuses.

Green/Brown runs to the rear of the car, most probably down the left side paired with the brake light wire. It may also be grouped with whatever runs to the heated rear screen, but that us a total guess.

I see several of the Plus 2S schematics show an alternative. The reverse switch is powered by a White wire leaving the central fuse box. Not sure how that setup would get to the switch though. Note this would appear to be a non-standard use of White, which is normally Hot in Run & Start - Unfused, running from the ignition switch to supply the fuse.

These are just best guesses. Let us know hiw you make out.

Hope it helps.

[dcmarsh]

Thanks! Will check.

[Bud English]

Stu- I don't think you want the backup switch wired to a hot at all times circuit. You could never leave the car parked in reverse.

The green wire on my 70 +2S transitions to a white wire going to a four way bullet connector common to the hot side of Brake Fail light, the Heated Rear Screen Switch, and the center fuse box (switched 12V in the IGN position). The hole for the grommet for the switch wires goes to the interior of the car, by the heater, and I believe the power comes from the interior as described above.

My loom is becoming non-stock as well. The old one is laying on the garage floor beside the car.

[stugilmour]

Good catch Bud. I was correcting myself even before I saw your excellent clarification. Am I correct in thinking the central fuse box is the one located in the dash ash tray spot?

Thanks for the correction.

[Bud English]

I think that Dave's 71 is probably like mine and has three fuse blocks with four fuses each, for a total of 12 (divide the number of extra lights on a +2S by seven to get the number of fuses). Okay, not really. The fuses are located in the engine compartment next to the pedal box.

[stugilmour]

Excellent. That makes more sense now.

As an aside, that darned reverse light switch wire is the easiest to forget when removing the engine & transmission.

[dcmarsh]

The wiring diagram (1st thin image below) shows a white wire going from the fuse to the switch, and a green/brown from the switch. It implies the switch connection is towards the rear of the car. Mine is red/black and a white, (2nd image below) and I can find nothing the length of the wire towards the rear of the car. The wires are also together in one bullet connector, which doesn’t match the 4 way one mentioned above, and shown on the wiring diagram.

The helpful comments do clear one thing up though, which is that the connection is behind the dashboard somewhere, and the feed to the reverse lights is back there as well. I don’t feel capable of a dashboard removal and rewire, unfortunately.

And yes I have the 3 fuse box version, divided by the square route of broccoli to determine the correct circuit.

Thanks for the tips!

[Bud English]

You shouldn't have to remove the dash. All the wires going to the rear run through the interior up against the side rail and across the top of the driver's foot well. You should have two loose wires in the vicinity of heater. The wires that you show in your picture go through this hole in the body near the bellhousing:

If you pull the carpet down in this area you should find both of your missing wires. They originally had bullet connectors, one male and one female. You're getting close!

The four way I mentioned is where the white wire that you are looking for gets its power. Your car has that male/female bullet connector on the switch pigtail. Mine has separate male and female bullets. You may find that the two wires that you are looking for have either separate bullets or the male/female mating connector to your switch pigtail.

[stugilmour]

Dave, is the reverse light bullet plug in the picture inside the car body, under the car proximal to the running gear, or somewhere in the under hood area? Perhaps the non-standard wire colours result from the switch and pigtail lead being changed out at some point? As I recall the stock switch wires are soldered on to the switch terminals, but it has certainly been a while since I have looked at the stock setup.

I can’t imagine the dash will need removal though. Bud can clarify, but in the Federal cars all the runs to the rear of the car are located inside the body. I can’t be sure for your model, but I expect the reverse light runs were located on the left side under the carpeting proximal to the soundproofing felts. Typically they terminate down by the pedals with a whole bunch of bullets.

Perhaps confirm you have Green/Brown at the tail light housing, and then hunt down the Green/Brown at the firewall connectors?

In any case, the reverse lights can be made functional without the transmission switch. I bodged mine to get going by temporarily installing a lever action micro switch under the console so it was closed by the shift lever. Worked fine for years and got.me through inspection and on the road.

Honestly just spitballing. Let us know how you make out. Hope this helps.

[dcmarsh]

Dave, is the reverse light bullet plug in the picture inside the car body, under the car proximal to the running gear, or somewhere in the under hood area? Perhaps the non-standard wire colours result from the switch and pigtail lead being changed out at some point? As I recall the stock switch wires are soldered on to the switch terminals, but it has certainly been a while since I have looked at the stock setup.

I can’t imagine the dash will need removal though. Bud can clarify, but in the Federal cars all the runs to the rear of the car are located inside the body. I can’t be sure for your model, but I expect the reverse light runs were located on the left side under the carpeting proximal to the soundproofing felts. Typically they terminate down by the pedals with a whole bunch of bullets.

Perhaps confirm you have Green/Brown at the tail light housing, and then hunt down the Green/Brown at the firewall connectors?

In any case, the reverse lights can be made functional without the transmission switch. I bodged mine to get going by temporarily installing a lever action micro switch under the console so it was closed by the shift lever. Worked fine for years and got.me through inspection and on the road.

Honestly just spitballing. Let us know how you make out. Hope this helps.

Thanks, Stu!

The wire comes from the transmission under the car and in the picture I have it pulled into the engine compartment and held there temporarily with a wire so I don’t lose it. You can see the exhaust header to the left. The black at the top is the upper heater hose coming from the thermostat housing. I have the wire pulled to it’s max length just to show how far it goes, which isn’t far enough to get anywhere near the wire broccoli by the fuse boxes. You guys have confirmed it shouldn’t go into the engine compartment.

Yes, I’ve confirmed the correct Green/Brown wires in the twilight housing, but haven’t found them in the mass of spaghetti under the steering wheel, but I haven’t checked where Bud’s picture suggested but will do that next.

Will post what I learn.

Dave

[dcmarsh]

You shouldn't have to remove the dash. All the wires going to the rear run through the interior up against the side rail and across the top of the driver's foot well. You should have two loose wires in the vicinity of heater. The wires that you show in your picture go through this hole in the body near the bellhousing:

Reverse Switch Wire Entry.jpg

If you pull the carpet down in this area you should find both of your missing wires. They originally had bullet connectors, one male and one female. You're getting close!

The four way I mentioned is where the white wire that you are looking for gets its power. Your car has that male/female bullet connector on the switch pigtail. Mine has separate male and female bullets. You may find that the two wires that you are looking for have either separate bullets or the male/female mating connector to your switch pigtail.

Thanks much, Bud, especially for the picture. Will check that next, as soon as I can warm up the garage enough in the next day or two! Will post progress.

Dave

[dcmarsh]

Here is what my drivers side floor and tunnel looks like. The only hole appears to be a drain hole in the middle of the floor. Don’t see any unconnected wires hanging down but I’m going to request a younger relative who is still flexible to lie down underneath and check further! The passengers side would be closer to where the wire comes from the transmission so will check there next.

71 +2S (U.S.) driver’s footwell

[Bud English]

The hole is higher on the tunnel, up by the heater on the sloped portion of the firewall near the bellhousing. It faces forward and downward. It's definitely on the driver's side (US). You can actually see it from the engine bay. Here's a wider view.

[dcmarsh]

Found it! Thank you Bud and Stu!

Will be posting my next dumb electrical question with a drawing shortly, but in a separate topic. A mysterious voltage drop at the source end of the ballast resister.

Dave