High Beam Headache

[Walluski]

Howdy,
My 1972 Series 3, 2+2 is giving me a high beam headache.
The high beams were working about a week ago. Now, the low beams work fine but the head lights go out when I flip the high beam 'dip' switch on the dash. The 'blue' indicator light comes on, but the lights go out.
I tried pulling the turn signal indicator and same story. The blue light comes on, the lights go out.
I've checked the fuses, all good. I checked the wiring at the switches and it is all solid connections and looks correct against some of the MANY reference pictures I have (including my own of this car).
I haven't ruled out a simultaneous failure of both high beam bulbs in the lights themselves, but this seems unlikely.
I'm not sure what to do next. I don't know if these cars have relay switches for the headlights? It feels like a loose ground wire somewhere, but I am novice and wouldn't know where to start looking.
I got behind the 'dip' switch on the dash and checked those connections as well, all good. I guess it could be the switch, but wouldn't the turn signal pull still work?
Your help is very much appreciated.
Mark in Seattle.

[Ole-xke1974]

There's a big round connector inside the LH front wheel arch below the headlight. That carries all the cables for the headlights and indicators. It is prone to fail over time. It could be having bad connections and wiggle it might help. Mind you, if that is the culprit, you might be looking at having to fit a new connector.
Cheers ..... Ole

[Walluski]

I went through everything again.
Couple of things, the headlights don't flash with the emergency flashers (I'm not sure if they're supposed to).
I misstated in the first post, pulling the turn signal lever has no effect other than lighting the blue 'dip' light.
I rechecked the fuses and made sure of the voltage on the high beams and low beams on the fuse box.
I get 12.5v on the high beam fuse when the dip is on, but no lights.
Thanks to Ole, I checked the connector in the wheel well and it seemed fine. Jiggled it a bit. Pulled it out (it was smeared with dielectric grease) and reinserted with prejudice.
I think all that's left is the dip switch is defective? or both high beam bulbs are blown?
I also took 3 Advil for my headache. At least that worked.

[lowact]

Original did not have headlight relay. Pwr to the headlights AND the H/B indictor (blue) light is from the fuses after the dip switch. So it can't be the dip switch?

[chris420sa]

Hi Mark - have you taken a look at the wiring diagram which you can download from the Knowledge Base - Series 3? High beam lamp cct is on the LHS of the diagram. Also see SNG Barratt parts - "Other Electrical - harness"
It seems that you've checked the circular cable plug to the front of the underside of the LH wing and found no apparent fault but have you tested for continuity from the dip switch set on high beam to the cable plug "prong"? The prongs are numbered. If there's continuity there, then the fault is possibly at the wiring block connector (SNG B part number C2532) situated under the LH headlamp nacelle and which is "accessed" by removing the indicator lamp. This original connector block is for all of the lights' wiring and it's possible that there's a bad connection in that block - or perhaps the block is somewhat past its sell-by. (Obstetrics would be a helpful attribute when accessing.) I replaced my block with individual connectors for ease of fault finding but that was done when the headlamp nacelle had been removed for a respraying rather than trying to access via the indicator light opening.
It may also be possible (although I haven't tried it) to remove the 8 pin plug and socket retaining plate - Item 2 -part number C16997 (3 nuts accessed with some difficulty via the indicator lamp removal) and withdraw the block connector through the hole provided there's enough slack on the lamp wiring. To refit the retaining plate does require an assistant to position it (whilst you're lying in a very uncomfortable position getting neck ache) and hold it whilst you place the nuts.
Good luck and hope you find the fault - please let us know.
Best regards
Chris

[Walluski]

Well, I finally got around to testing the 'plug and socket' behind the headlights. Being a novice at this I'm not exactly sure what I found. When the highbeams are 'ON' (via the dip switch) with the harness plug pulled, I get 12.5v in the center prong of the plug. When the highbeams are 'OFF' I get zero volts on the center prong. I do get an on/off for a different prong (not sure what the numbering nomenclature is for these) with the lowbeams off/on so I am assuming that the center is carrying the highbeams and there is a fault either in the receiving socket or at the connector block behind the light. Shaking and jiggling and talking nicely hasn't helped.
Couple of questions: Does my diagnosis sound correct and I need to probably replace the connector block and/or the plug and socket? And, how difficult is this to do? It seems straight forward and I've got nothing but time so I'm up for it but I hate to go to the effort if I'm still looking in the wrong place.
To recap, I've checked the fuses, power on either side of the fuses, dip switch, and the rocker on/off switch and wiring. All of those have checked out OK. Also, I discovered that one of the headlights highbeams was burnt out so I have replaced both headlights. Then I went to Costco and got another big bottle of Advil.
Thanks for your help!
Mark

[lowact]

When headlights are on, side lights would also be on, so not much proved yet?
The centre pin is #4?
According to my wiring diag:
2 = high beam
3 = low beam
5 = side lamps
7 = RH flasher
8 = LH flasher
The others don’t feature. The wiring diag suggests that the supply to the rear sidelights is from the front sidelights, i.e. back through the plug, however I can’t readily believe they would do this.
Don’t bother trying to dismantle the plug to see which (colour) wires are connected to which pin – the black plastic sheath is crimped into the back of the plug.
You have replaced both headlights, did u check the headlight plug?

[Walluski]

Thanks Colin and to answer your question, nope I did not check the three prong plug for the head lights when I installed them (slaps forehead). Seeing as replacing the headlights was probably the easiest undertaking I've had since acquiring the car, I will pull the headlights today or tomorrow and check.

[Walluski]

There is no power at the three prong plug that connects to the headlight for the highbeams.
My 8 pin connector cable is missing two metal inserts. Is that correct? (see picture).
The center socket pin shows 12v when the highbeam dip switch is on, 0v when the switch is off.
I tested the socket for low beams, flashers and turn signals and got 12v for all when on. Someone told me the center socket is not used, yet I get 12v there when the highbeams are turned on?
I pulled the large metal cover off the back of the headlight assembly to get a look at the terminal block. Nothing loose or obvious and no signs of corrosion (see picture).
I hate to replace the socket and/or the terminal block, especially when I'm not sure it will solve my problem.
Any other suggestions?
Thanks

[lowact]

I’m calling the connector with the holes the plug and the one with the pins the socket.
My car is ’72 us spec, I imported it, should (?) be the same as yours. My plug is not missing any metal inserts, each hole on the plug (and pin on the socket) is labelled with a number, 1-8. Holes 1-4 are slightly larger than holes 5-8.
It may be that a previous owner of your car had some issues that he fixed by making modifications…
You can tell what the wires do by their colours, as per the wiring diag, as Chris advised, you can download this from the forums knowledge base.
https://www.dropbox.com/s/a4ubnltt94dnq ... g.pdf?dl=1
Blue with white trace = high beam
Blue with red trace = low beam
Red = sidelamps
Green with red trace = left flasher
Green with white trace = right flasher
Black = earth
You can verify any part of a circuit by continuity test. E.g. between a pin on the socket and a terminal on the headlight plug. Isolate the circuit and use an extension wire to connect both ends back to your multimeter and measure the resistance. If the wire is good you will get a resistance of a few ohms. If the wire is broken somewhere you will get an “error” or open circuit reading.

[Walluski]

First, thank you Colin. I really appreciate the help and your patience with me. I'm enjoying the learning experience and looking forward to solving this problem. When I started I new little or nothing about car wiring and am only slightly better now, BUT I am getting much better at reading wiring diagrams.
OK, I think the problem is two parts. The piece that 'plugs' (holes) into the socket (pins) is missing the metal inserts and not able to make the correct connections. Secondarily, the 'socket' has been modified and doesn't match the wiring from the harness.
I think you are correct that this was modified by a previous owner and I'm not sure what they were trying to accomplish. On the socket side there is a short 'purple and yellow' wire coming out of the center pin (see picture) it is then connected to a 'red and yellow' wire and then sent back to a different pin. This makes no sense to me at all.
I disconnected the 'purple and yellow' wire from the socket and connected the blue and white headlight to that pin and 'voila' high beams. However, low beams wouldn't work.
So, my plan is replace the 'plug' and the 'socket' and put them back to the original wiring diagram. The wiring harness looks original so I'm hoping the wiring inside of it is original too.
I'm thinking as long as the wiring from the plug matches the socket, I should be good to go.

[lowact]

Seems to me you have proven that the problem is exactly as Ole predicted, broken pin/hole connections in this plug.
Seems PO work around was to reroute the headlight supply from pin 2 or 3 to the centre pin 4 – via purple/yellow, red/yellow wires on the back of the socket. If this is correct u should find that there is similar rerouting on the back of the plug?
That low beam stopped working could be a lot of things, including that the PO found not enough reliable connections to run everything, so he kept low beam and didn’t connect high beam.

[MSM]

Congratulations to Mark and Colin for working together and finding the solution to the problem. This is what these forums(fora?) are all about.

Just to satisfy my curiosity can anyone tell me if the bonnet connector in Mark's car is original or has it been replaced at some time? The reason I ask is that the connector shown is the type that SNG Barratt now supply with solid brass plugs and sockets with grub screws to retain the wires but the original connectors, certainly on Series 1 and 2 cars, used folded sheet brass pins and sockets with soldered connections. I am just curious if the solid connector version was used as standard in Series 3 cars or if is is a modern replacement.

[Walluski]

Hmm.
Looks like there is no wire in the harness for the fog lamps.
I'm not sure if that means the harness is wrong or the fog lamps are wrong but it explains why the high beams were wired as they were.
Apparently the PO took the wire from the high beams and ran that power to the fog lamps. I guess he wanted them to work and figured the high beams were a trade off.

Anyway to power the fog lamps from the harness without running new wires? Or am I missing something here?

Thanks
Mark

[Mephistopheles]

Hi Mike,
series III has the same connector comprising of folded sheet pins like series I and II, see photo of the refurbished connector of my series III. Before refurbishing it I had to experience the unsatisfactory quality of a repro part with solid brass plugs.
Regards
Holger

[MSM]

Thanks Holger - that is interesting and your refurbished connector looks beautiful.

[Walluski]

Thought I'd post a final note.
I ended up replacing the terminal block (it fell apart into pieces when I handled it).
Then I replaced both sides of the non-original 'replacement' wiring connector (nothing original here apparently). That said, everything works now as it should.

I sure like the look of Holger's refurbished plug, but I didn't have the original to refurb and I couldn't find an alternative?

Thanks again to Colin and Ole for the guidance.

Cheers,
Mark