Which rear lights should be on? Options

[watsonrx13]

I'm having electrical issues with the rear lights and need some information for my 1974.

Please use the following numbers (from outside to inside).

1. side marker
2. tail light
3. brake light
4. back up light

A. Which lights should be on when the brakes are pressed?

B. Which lights should be on when the blinker switch is on?

C. Which lights should be on when the tranny is put into reverse?

D. Which lights should be on when the light switch is pulled on?

E. Which lights should be on when the light switch is pulled on and the brakes are pressed?

F. Which lights should be on when the light switch is pulled on and the blinker switch is on?

G. Which lights should be on when the light switch is pulled on and the tranny is put into reverse?

H. Which lights should be on when the light switch is pulled on and the brakes are pressed and the blinker switch is on?



How do I check the continuity of a circuit? Please use a very simple explination, I'm not real familiar with the electrical terms.

The following is the current wiring for the '74

Left side - driver side
row 1 (inside to outside)
(2) BR - ground
(1) BK/WH - turn signal

row 2 (inside to outside)
(2) WH/BR - back up
(2) BK/YW - stop
(1) WH/BK - side marker

Right side - passenger
row 1 (inside to outside)
(2) BR - ground
(1) BK/GR - turn signal

row 2 (inside to outside)
(1) WH/BR - back up
(1) BK/YW - stop
(1) WH/RD - side marker

-- Rob

[ejm]

The lights have seperate filments, they can all be on at the same time

Questions E thru H makes me think you have a ground problem

[watsonrx13]

OK, this wasn't a trick question, I was just trying to understand which light should be on....

So, I'll answer what I think they should be and if I'm wrong, can someone correct me?

A. 3
B. 1
C. 4
D. 2
E. 2,3
F. 1,2
G. 2,4
H. 1,2,3

-- Rob

[Porsche Rescue]

I think the side marker and the turn signal (which you don't include) are two different bulbs. Pull the lense and you should see (from left to right, looking at the driver side assembly):
side marker(1), turn signal(2), tail/stop(3/4), back-up(5).
I am doing this from memory, but if I recall correctly, the stop/tail is a dual filament bulb (your 2 and 3 are the same bulb). The others are single.
So, using your questions and my numbers:
A 3/4 (bright filament)
B 2
C 5
D 1 and 3/4 dim filament
E 1 and 3/4 both filaments
F 1 and 3/4 both filaments and 2
G 1 and 3/4 dim filament and 5
H 1 and2 and 3/4 both filaments

Testing of voltage or continuity is done with a volt/ohm meter. Very inexpensive at Radio Shack.

[John]

There is another bulb/filiment you are leaving out.

Stop bulb/filiment

The side marker bulb is a smaller bulb mounted near a side reflector.

The Turn Signal/Tail Light is a dual filament bulb.

The Tail Light/Side marker bulbs are wired together (illuminate together)

Looking at a Tail light Housing from the rear. From outer to inner

1. Side marker (small bulb)
2. Tail light/Turn Signal (dual filiment large bulb)
3. Stop (large bulb)
4. Backup Light (large bulb)

A - 3 (bright Filiment)
B - 2
C - 4
D - 3 (dim filiment), 1
E - 3 (bright filiment), 3 (dim filiment), 1
F - 2, 3 (dim filiment), 1
G - 4, 3(dim filiment), 1
H - 3(bright filiment), 2, 3(dim filiment), 1

And when you are in reverse, with the lights on, and turn signal switch on:

1, 3 (bright filiment), 3 (dim filiment), 2, 4

Please don't ask me to do that again from memory.....

[Porsche Rescue]

John may be right. There is one dual filament bulb in the mix. Could well be turn/tail rather than stop/tail.

[John]

no Jim, you were right. It is a stop/tail. I fixed my post as quickly as I could.

[watsonrx13]

Thanks guys, this really helped. I got the lights working correctly....

-- Rob