No taillights?

[Fast68back]

So I was working on the lights this weekend and I have nothing at the back of the car, outside of the emergency flasher circut. No taillights, brake lights or turn signals. Just hazards. At first I thought maybe it was the flasher, I have Mustang project taillights with the sequential flasher. I replaced it today with a standard flasher and still nada. The other odd thing is the reverse lights come on when I turn on the headlight switch. I have two headlight switches and both do the same. I guess that leaves the turn signal switch as the culprit? One side note, the brake light switch is not connected to the brake pedal, but the connector is connected to the switch, its just dangling. What am I missing?

[Midlife]

Well, all of your taillight power (brakes, turn signals) comes through the brake light switch, so if it ain't connected, you're gonna get squat.  The e-flasher bypasses the brake light switch.

That said, your headlights should provide running lights, which don't go through the turn signal switch.    Your backup lights should be completely independent of your headlight switch, turn signal switch, and brake light switch.  Most aftermarket LED tailight systems won't work with standard flashers, because there's not enough resistance for the flashers to work.  Some will work as long as your front lights haven't been changed to LEDs. 

You need an 'electrical guru to go through your wiring and make sure it's correct.  Golly gee, I wish I could recommend someone...

[Fast68back]

One side note, the brake light switch is not connected to the brake pedal, but the connector is connected to the switch, its just dangling. What am I missing?

[Sluggo]

The brake lights and flashers are on the same filament and get their power from the same source, the turn signal switch.

Your ground is most likely working since the backup lights come on even if it is when the headlight switch is on.

Stop light switch is irrelevant as far as being mounted.

Sounds to me like you have your running light circuit crossed or shorted to the reverse lights. You sure that connector we used to wire the msd box to was not the backup switch connector? That might explain the ignition problem as well.

[Fast68back]

No, its not the connector we used for the ignition. It sounds like the two plugs for the taillights and reverse lights are swapped, but the wires are the same colors so I dont see how they could be and if they were, wouldnt the reverse light blink with the turn signal on? I think the back up lights are on because the back up light switch is not connected so its open, closing the circuit, however that does not explain why they only come on when the headlight switch is "on"

[daveSanborn]

I've had some minor electrical issues before, but man this one takes the cake.... the reverse lights come on when the headlights come on?  Holy crap!

Is this new wiring or are you using the existing?

[Fast68back]

Its the original wire harness. There are the two plugs that connect the rear harness to the main harness and you would think they were swapped, but they arent. The wires match up as far as th colors and IIRC the plug ends are different in that the plugs coming from the rear assy, one has male connectors and the other has female, the main harness has the same to avoid connecting them incorrectly.

[daveSanborn]

I suck at troubleshooting electrical problems.  The only success I have is when I break out the schematic and my test light..... and even then it's usually a frustrating experience.

Which reminds me.... my fan speed switch for my blower motor is inop.  Brand new fan motor, brand new wiring (except for the switch harness).  Worse than TS electrical problems is when you have to lay on your back to get up under the dash to fix them. 

[Midlife]

Putting aside the connectors at the bottom of the steering column (where the turn signal switch interfaces with the rear lights), it is relatively easy to confuse the running lights (from the headlamp switch) with the backup lights.  The running light wires are black (bad choice...usually black is ground), and the backup lights are black with a small red stripe.

I apologize for not catching that the stop lamp switch was connected but not installed; you will not get stop lamps until you initiate the switch.  You should get turn signals, however, IIRC.

[Fast68back]

  it is relatively easy to confuse the running lights (from the headlamp switch) with the backup lights.  The running light wires are black (bad choice...usually black is ground), and the backup lights are black with a small red stripe.

So they are both four prong square connectors? Hmm, I'll have to dig around up there some more and see if I have one not connected. I know there is the one for the reverse switch which also powers the backup lights. I do know I was havin a helluva time trying to connect the reverse switch to the plug.


@%#*, now I want to leave work and go look....

[Sluggo]

No, its not the connector we used for the ignition. It sounds like the two plugs for the taillights and reverse lights are swapped, but the wires are the same colors so I dont see how they could be and if they were, wouldnt the reverse light blink with the turn signal on? I think the back up lights are on because the back up light switch is not connected so its open, closing the circuit, however that does not explain why they only come on when the headlight switch is "on"

How can it be open...closing the circuit?
If the backup switch is not connected the circuit is open period. They would be on all the time not just when the headlight switch is on.

Do I need to bring the power probe up there?

[Sluggo]

I suck at troubleshooting electrical problems.  The only success I have is when I break out the schematic and my test light..... and even then it's usually a frustrating experience.

Which reminds me.... my fan speed switch for my blower motor is inop.  Brand new fan motor, brand new wiring (except for the switch harness).  Worse than TS electrical problems is when you have to lay on your back to get up under the dash to fix them. 

Works on high only?

[Fast68back]

How can it be open...closing the circuit?
If the backup switch is not connected the circuit is open period. They would be on all the time not just when the headlight switch is on.

Do I need to bring the power probe up there?

Because there is no switch on the end, the two wires are just hanging there. The T5 does not use a "switch" like the stock 3spd or the toploader that was in there, it has two prongs on the side of the case that the wires connect to. However, reading Mids reply, I'm thinking its not that at all, its get the 12V for the rear lights and not from that switch. I did mis-speak in saying it was open/closing the circuit. I did not recall how the reverse switch worked, if the probe was depressed or extended to close the loop.

[Sluggo]

Looking at the diagram there appears to be two 2 pin connectors in the trunk. Could these be swapped?
One is backup and one is brake/turn

[Fast68back]

No, the taillights come right off the harness, no connectors, there are two, 2 pin connectors, one for each of the backup lights.

[Sluggo]

Because there is no switch on the end, the two wires are just hanging there.  

Thus the circuit is open and the reverse lights should not function at all. Regardless of whether the switch is normally open or closed,
there is no connection.

It looks like the reverse light switch is also a starter interrupt. Did the original set have to be in reverse to start?
 

[Fast68back]

Thus the circuit is open and the reverse lights should not function at all. Regardless of whether the switch is normally open or closed,
there is no connection.

It looks like the reverse light switch is also a starter interrupt. Did the original set have to be in reverse to start?
 

Its not a starter interrupt, its a four prong plug, but two wires jumper, the other two go to the reverse switch. However the car will not start with the connector diconnected, ask me how I know......

[AzPete]

I wonder if the tail lights are actually grounding thru the back up lights, causing them to light. Double check the ground wires on the tail lights. I have seen this before. Also, disconnect the back up lights and see what the tail lights do.

Looking at the schematics, there appears to be a grounding lug in the trunk area for all the lights. Is this good?

[Fast68back]

yes, they share the common ground that is right by the fuel filler tube. I'll try disconecting the back up lights. I'm very curious about Mids suggestion thouh, it kinda makes sense, which really confusses me........

[daveSanborn]

Works on high only?

No, it doesn't work at all, which should help me figure out whats going on.  I mean it's not like I turn the fan motor on and my reverse lights illuminate or anything mind blowing like that.

[Midlife]

No, the taillights come right off the harness, no connectors, there are two, 2 pin connectors, one for each of the backup lights.

Quite right: each backup light has a hot (black/red) and a ground (black).  The running lights (black wire) is a single lead connecting at the bottom of the turn signal switch.  This is where I think you've mixed the backup lights and running lights.

[Sluggo]

You did not put 1157 bulbs in the reverse light sockets did you?

[Sluggo]

No, it doesn't work at all, which should help me figure out whats going on.  I mean it's not like I turn the fan motor on and my reverse lights illuminate or anything mind blowing like that.

I would be guessing a fan switch or power issue.

[Fast68back]

Quite right: each backup light has a hot (black/red) and a ground (black).  The running lights (black wire) is a single lead connecting at the bottom of the turn signal switch.  This is where I think you've mixed the backup lights and running lights.

But the plugs for the reverse lights are in the trunk and this one is at the turn signal switch?


I used the bulbs that came with the new back up light assemblies. I tried unplugging the back up lights to see if they were drawing everything and got nothing. I need to break out the manual to see the TS switch wiring.

[Midlife]

Well, the tail light harness has two ends: one at the turn signal switch, and the other at the tail lights.  I believe you have plugged the running light lead from the headlamp into the backup light connector near the turn signal switch.  Your reverse light pig tails are plugged into the correct connectors near the tail lights, but that signal is incorrectly connected at the other (long) end of the tail light harness.

Does that make sense now?