Headlights not working

[gemmalou]

sorry if this has been covered before,
We have bought a Minor a few months ago and the side lights were rusty so I repalced them and had to rewire them, I have had problems with the headlights not working.
so far it has new sidelights/indicator holders and wiring - both side lights and indicators now working
new light switch - sidelights front and rear working
Headlights have had new bulds and wiring harness's but not working
We have a 1960 Minor
any help please

[simmitc]

Do you have a multimeter to help with diagnostics? Do you have a wiring diagram? The circuits are simple, but there are a few places where a loose connection will stop the lights from working. Note that there are no fuses n the lighting circuit.

Even though it's tempting to jump straight in, it pays to be methodical. At the new light switch you should have one thicker blue wire coming from the fusebox area and another that goes to the dip switch. With the switch on for headlights, there should be 12 volts on the terminals to which the blue leads are connected. When "off", 12 volts only on the supply lead, not the one to the dip switch. If you cant get that setup, then are there other terminals that you can use? The meter can help you identify which terminals connect at each stage of the switch.

As you have replaced the switch, and that is the first place where a single wire can affect all four head lights (dip and main, kleft and right), that is the most likely place for your trouble.

If the above is all correct, then move to the dip switch and check that 12 volts is present on the feed from the lighting switch and to main beam (blue/white wire) and dip beam (blue/red wire), depending on the position of the switch.

With 12 volts correct at the dip switch, move to front right hand corner of engine bay and check for 12 volts at the connectors where the wires split to each side of the car, and then lastly to the headlamp itself. If you have 12 volts there, then the bulbs have blown (the meter can test that) but I would be amazed if all four filaments had blown at the same time.

[gemmalou]

Thankyou, yes I have a multi metre so will try that I also have a power probe and tested the lights and the wiring harness and all work using the probe. I do have a new dip switch so I will change that but the wires on the back of the light switch are red I know these are not original but this is also why I have bought some new harness which have the correct wiring

[geoberni]

Thankyou, yes I have a multi metre so will try that I also have a power probe and tested the lights and the wiring harness and all work using the probe. I do have a new dip switch so I will change that but the wires on the back of the light switch are red I know these are not original but this is also why I have bought some new harness which have the correct wiring

RED wiring on the Lights switch is correct colour for the Side Lights.
BLUE is for the headlights; at the Dip Switch it splits into Blue/Red & Blue/White for DIP and Main respectively.

Simmitc has given you a lot of good pointers, but don't neglect the Earth connections.
The number of times people go off on wild goose chases, replacing bulbs, wiring, connectors/terminations.... and then it turns out to be a broken/bad earth....

[simmitc]

Berni has a very good point. The earth is made by bullet connectors into clips bolted to the body, and these can corrode or the clips break; but again, it is unusual for both to fail at the same time. The switch controls both the side lights (red wires) and headlights (blue wires) and some switches have additional terminals, so it can be easy to get the wrong ones.

[oliver90owner]

Do be aware that voltage is not necessarily a measure of the usefulness of a circuit - it also requires a current capacity. Any circuit should have a 12V voltage drop across the device being powered, not across any other part of the circuit.

For instance, a low wattage test light may well be illuminated, but that same current through a 50W lamp may not even make it glow dimly.

[gemmalou]

thankyou for the replies, I have been out on my Minor today with a multimetre I have 12v going into and coming out of the light switch and also have the same at the dip switch.
I know the headlights work and the light harness all works as Ive tested with a powerprobe so its the wiring in between so has anyone any ideas,
sorry to ask I was trained as a mechanic mainly working on older cars but unfortunetly about 15 years ago suffered a brain tumour which also has effected my eyesight so any help or hints Im very thankfull for

[geoberni]

At the moment I'm working on the assumption that you either have standard original headlamps or perhaps halogen replacements.
Now I don't have experience of the latter cars, which I believe have the dip switch wiring under the carpet, but I'm guessing your car has the earlier type switch, with the connections in the engine bay.

This bit confused me,

the light harness all works as Ive tested with a powerprobe so its the wiring in between so has anyone any ideas,

Where was the power coming from to use a 'powerprobe'??


But to continue....
You said you have 12v 'at the dip switch'. There is a possibility that the Dip Sw has failed....
Looking at this diagram, the 3 points arrowed in Blue are the connections to the Dip Sw, 1 input (Blue) and 2 outputs (B/W & B/R).
So with the Lights sw ON, there should always be 12v on the Blue, and the output with be either on the B/W or B/R depending on the operation of the Dip Sw.
You should have 12v available at each of the points marked with red, while operating the Dip sw.

Lights1.JPG (60.55 KiB) Viewed 1083 times

The Lamps are 31/34 Main Beam and 36/37 Dip Beam.

If you have the right outputs from the Dip Sw, then switch the Lights off and pull apart the B/W and B/R connections at the Dip Sw.
Use a multimeter to check those connections to earth, i.e. check the continuity of the wiring via each pair of lamp filaments, the reading should be very low with 2 identical lamps in parallel, probably only around 2-3 Ohms. If it's much higher than that there's a wiring fault, which you'll need to trace by breaking the circuits at subsequent break points on the inner wings.

I hope that's kept it simple but understandable, it's difficult writing this sort of thing down without it turning into a huge tome of writing.

Incidentally, I made a video during lockdown of taking an early Dip Switch apart to fix it....
https://www.youtube.com/watch?v=jCTcLwJVuDs

[simmitc]

Like Berni, I'm a little confused by hat statement; but if I understand correctly...

You have tested the bulbs in a completely separate environment. Either you have continuity between earth and dip, and earth and main, but nothing between dip and main. OR you have connected earth and the other terminals one at a time, and the lamps illuminate correctly.

The harness has 12 volts along its length, but where have you measured? Is it going into the harness at the dip switch, at the junction between the dip switch harness and the main harness (behind the driver's glovebox), at the 3-way connectors on the inner wing, or where the lamp fits in? These are the only places that I can think of where you might havbe a connection issue.

[gemmalou]

Thankyou everyone,
The powerprobe is a tool that is connected to the battery so you can either send positive or negitive power to but I have now found out the problem
the wiring had been meesed about with by a former owner and messed about with very poorly
I have a feed into the dip switch and both main and dip beam feeds out of the dip switch but the main and dip switch wires in the main loom have been cut for some reason so I will now check the main loom and replace those wires and try to find some correct type sleeving for the main loom,
hope this makes sence

[simmitc]

Well done for finding the problem. Make sure that you use the correct grade and colour wiring to effect the repair to make it easy for anyone else having to look at it.

[geoberni]

Glad you found it.
I think many of us find the occasional 'strange' thing has been done to our car by a past owner, but a couple of cut wires to the headlights is certainly one of the more unusual.

Though far easier to fix than what I found....
It took me a couple of years to discover that when my car was rebuilt in the late 1990s, they didn't fit adjusters to the Torsion Bars, they've each got a single bolt into the cross member .
One day I'll get around to cutting some slots in the right place
I flagged it up on here back in 2019 (I brought Basil in 2017) viewtopic.php?t=70626