Electrical (Blinkers) Question ???

[TWJ]

I'm trying to work out an electrical gremlin with my blinkers/flashers (not grounds, not relay, not bulbs but blows fuses) and need a little help:

Since my blinkers aren't working I can't tell...is the blinker/flasher on the passenger side rear socket 1 or socket 2 in the image below?

If socket 1 is it tab A or Tab B?

General question:
Shouldn't all bulb sockets test as "infinity" for ohms even with everything off? Every bulb socket on the car does EXCEPT tab B in the image below. Does this mean anything? It's the same on both sides, rear only. ????

[NeunElf]

The L-57 wiring diagram suggests that the inboard one [A] is the brake light and the outboard one [B] is the tail light. With luck, they'll have terminal numbers.

Yes, without bulbs you should see infinite resistance. Low or zero resistance is a short.

Right Rear Light on L-57 wiring diagram

Yellow Black brake light [58]
Grey Red Tail Light [54]
Grey Brown Backup
Black Green Right Turn [49R]

[TWJ]

Thanks Jim!

So the blinker socket in the pic is socket "2"?

I sorry, what do you mean by terminal numbers?

[NeunElf]

Thanks Jim!

So the blinker socket in the pic is socket "2"?

Yes, the turn signal/blinker is #2, the tail light-stop light is # 1 and the reverse light is in between.

I sorry, what do you mean by terminal numbers?

Bosch Terminal Designations (DIN Standard 72 552) are those numbers on the wiring diagram. It seems that the designations in 1966 aren't all the same as they are now so if you Google for a list it won't always match a SWB 911.

You'll have to forgive me for not pulling a rear light from my car to confirm they're on the rear light unit but those numbers are usually molded into plastic parts beside the terminals. If there's a 54 by the "B" terminal there's no doubt "B" is the brake light.

It happens that some replacement lights are for sale on this forum right now: NOS BOSCH 64-68 set of lights plus an xtra nos one for a terrifying price.

[TWJ]

Thanks again Jim, great information.

Actually the car I'm asking about is my '72 not the '66.

One more question: So socket 2 for the turning/emergency should register as open with bulbs out and ignition off? Measuring using the side of the socket and the tab.

Currently all 4 register as closed (0 Ohms). ???? Does this indicate a short?

[NeunElf]

Thanks again Jim, great information.

Actually the car I'm asking about is my '72 not the '66.

One more question: So socket 2 for the turning/emergency should register as open with bulbs out and ignition off? Measuring using the side of the socket and the tab.

Currently all 4 register as closed (0 Ohms). ???? Does this indicate a short?

Oops. I should have recognized that the lens off the light housing implies a LWB car.

Later wiring diagrams are also available at Rennlist. My documentation just covers SWB cars so I'm not certain whether you should use SL 33 or SL 35.

Zero ohms (short circuit) doesn't sound right but all four? That implies that four separate sockets or four separate wires back to switches and relays are all shorted. I guess physical damage or fire damage could do that but it mightn't be the most likely cause.

Maybe you could pull the housing, disconnect the wires, remove the bulbs and check the hot terminals resistance to the ground terminal. All of those should be open circuits [very high or infinite ohms] without the bulbs.

Similarly, with all the circuits de-energized:

1. ignition off,
2. transmission not in reverse,
3. brake pedal not depressed,
4. turn signal centered,
5. lights off

the ends of the power wires to the rear lights should have very high or infinite ohms to ground.

I fear there may be something wrong with you test methods but I can't put my finger on it.

[TWJ]

Maybe I have my terms wrong...could be. With ignition off and all 4 bulbs removed I test each socket by placing the black lead against the side of the socket then touch the tab at the back of the socket with the red lead. With all four sockets the needle on my tester (image below) moves from the position shown (on the left) all the way to the opposite side on the right. Just as if I just touch the two leads together. This is with the dial set to the "1K" position.

More info:
The fuses blow as follows noting that the same happens with all 4 bulbs in or removed:

Fuse #2
- With ignition on or off.
- When the emergency flasher switch is activated.

Fuse # 8
- With ignition is in position 2.
- When the turn signal switch is activated, either side.
- Note that when ignition switch is in position 0 or 1 and the turn signal switch is activated (either side) the running lights turn on for the appropriate side and the fuse does not blow. I believe this is correct (European parking lights?).

Also note that I have replaced the relay with a new Wehrle brand one. With the old relay in the fuses do not blow under any condition but no flashers either. At first I though I had gotten a bad new relay but I bought a second one which gives the same result.

[NeunElf]

Maybe I have my terms wrong...could be. With ignition off and all 4 bulbs removed I test each socket by placing the black lead against the side of the socket then touch the tab at the back of the socket with the red lead. With all four sockets the needle on my tester (image below) moves from the position shown (on the left) all the way to the opposite side on the right. Just as if I just touch the two leads together. This is with the dial set to the "1K" position.

More info:
The fuses blow as follows noting that the same happens with all 4 bulbs in or removed:

Fuse #2
- With ignition on or off.
- When the emergency flasher switch is activated.

Fuse # 8
- With ignition is in position 2.
- When the turn signal switch is activated, either side.
- Note that when ignition switch is in position 0 or 1 and the turn signal switch is activated (either side) the running lights turn on for the appropriate side and the fuse does not blow. I believe this is correct (European parking lights?).

Also note that I have replaced the relay with a new Wehrle brand one. With the old relay in the fuses do not blow under any condition but no flashers either. At first I though I had gotten a bad new relay but I bought a second one which gives the same result.

I have a feeling the problem might be the new relay. Maybe the "pinouts" on the new relay are different from the old relay and you've generated a short by hooking it up the same as the old relay (the wrong way).

Another possibility is that the new relay functions differently from the old relay.

Does the new relay have DIN pin numbers or a printed or molded circuit diagram?

Do you know anybody who can take a power supply (or battery) and a voltmeter and "map" the relay? I don't think I'm good enough to describe that process although I could do it.

[TWJ]

I first thought the problem was the new relay so I bought a second one and it acts the same way. The old relay and the new relay(s) both have terminal designations (numbers) next to the pins and the old and new are identical. They are also the same part number.

Also, I put the old relay back in and with all 4 bulbs out the sockets test the same (closed, 0 ohms) as with the new relay.

Emergency flasher switch?

Do both circuits pass through the turn signal switch on the steering column?

Is anything else common to both the turn signals and the emergency flashers?

[NeunElf]

I first thought the problem was the new relay so I bought a second one and it acts the same way. The old relay and the new relay(s) both have terminal designations (numbers) next to the pins and the old and new are identical. They are also the same part number.

Also, I put the old relay back in and with all 4 bulbs out the sockets test the same (closed, 0 ohms) as with the new relay.

Emergency flasher switch?

Do both circuits pass through the turn signal switch on the steering column?

It looks like (both SL33 and SL35 wiring diagrams) the emergency switch and the turn signal are parallel sources for the right and left indicator lamps. They join on the front trunk side of one of the connectors through the front of the people compartment.

By the way, if I'm reading the diagrams correctly, only the front turn signals are fused.

Is anything else common to both the turn signals and the emergency flashers?

I can't see anything, but I'm afraid I'm also having trouble finding a relay for the turn signals or emergency flashers on either SL33 or SL35. I can only find a headlight flasher relay and a horn relay.