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Hallo Everone,

I've recently bought an S-type, 1966, 3.8 m/od and am systematically (hmmm!) working through the faults noted so far. As with all classics I've owned, it's not a huge list but does need sorting.

As the title says, the sidelights will not switch off. They did when I bought it, I sat admiring it from a cafe window on the way home & they were off then.

At the moment, I'm using the battery isolator switch when it's parked up, but it's a nuisance to have to go under the bonnet each time I stop.

I cannot find anything online or in the workshop manual with respect to parking lights.
I've checked all connections, earths, etc & think this just leaves the headlight switch as faulty. There is a diode (?) connected to one of the wires on the switch & the casing seem to have a big crack in it.

Can anyone point me in the right direction here & also explain what the diode is for? Or has the car got a parking lights setting that I haven't worked out yet?

many thanks, Peter.

Hello Peter,

the master light switch is where I would look at first, the side lights are red wires and the heavy brown\white is the main feed into the switch. Is the diode? connected between the terminals with the blue wire and the red\yellow? Blue is the feed to the dip switch and red\yellow is the fog lights. Just wondering if someone has modified the circuit so as to have the option of having both on together?

Alec

Alec, thanks for the reply...

the colours are extremely faded and I can't make them out. The terminals are the 2 furthest away when the centre panel is folder down.
I can say that the headlights & foglights work independently of each other as I think they should. Fog lights don't work well wehn the headlights are on, in my opinion.
There is a big crack in the diode, though...

Hello Jackois,

it's a very long time since I looked at my light switch so I can't comment on the positions. I think I would remove the diode, as I don't know why it is there. There is a resistor which is used on the automatic or overdrive warning light, but there should be no supply to that with the ignition off.

I would think the most likely cause is the switch itself and if you have a meter should be relatively easy to prove?

Alec

Hi Jackois
I agree with Alec that this is most likely a switch fault. There is a 47 ohm resistor between terminals 2 and 10 on your light switch that is part of the overdrive warning light circuit; this has a set of coloured stripes painted on it - yellow, violet, black silver in that order. The body is usually a dark brown colour. If you have a diode wired to your light switch this will be an addition by a previous owner, but I am not sure what function this would serve unless you can find out which terminal number(s) it is attached to. Any diode would have to be reasonably meaty to take lighting circuit current; the diode body is usually black and there should be a silver or white stripe at one end, or maybe a + sign.
Best wishes, David

Ah! Now that may throw some light on the resistor fitted.

The car was originally an automatic, confirmed by chassis number & the fact it has the 'hold' switch to the right of the steering wheel. It seems to have been a quality job as the steering column shroud was installed with the overdrive & indicator lights fitted.

The car is going into a local specialist on wednesday for a 'look over' & a safety check as it hasn't done more than a couple of hundred miles a year for the last 7 or 8 years, as evidenced by it's past MOT forms.

Once it's back, I'll try ordering a new switch, fitting it, & will report back.

Other than the leaving the sidelights on, was there a parking light setting anywhere?

Hello Jackois,

unless the 'S' Type has a different switch my MK2 manual gives the switch positions as off, side lights, headlights and side lights, fog lights and side lights with no mention of parking lights.

Alec

Firstly, thanks for all the responses.

Investigation of the diode(!) has proved it to be the resistor mentioned in a previous post. As also stated, the colour coding shows this to be a 47 ohm (10% variation) resistor which is definately damaged through age/disturbance.

Obviously this will need to be replaced as it's there to stop the overdrive warning light from burning out (I assume when the lights are on). Searching online gives a variety of these, with varying wattages. Does anyone know what wattage I should buy?

Also, would anyone know if this resistor being broken would cause the original fault (side lights not switching off)?

many thanks

Hello Jackois,

the parts book has it as a 2W lamp, and with the resistor in series it will be less. Depending what resistors you have found but something about 2W should be ample. I don't see how this can keep your side lights on as that part of the circuit is only live with the ignition on, unless of course it has become displaced and is shorting from the live to the side light switch contact?

Alec

Or perhaps the +ve cable is fed by accident from an incorrect live tag on the switch?

Closed circuit contact burn outs are also possible. Switches of this age can become notoriously unreliable.

Mike

Hello all,

reporting back with regards to fitting the new resistor & no change with respect to the sidelights. New switch to be fitted for the next step & a further report back when done.

On a similar note, electrical, should the front doors have spring switches for the courtesy lights? My rear doors have them, but not the fronts. A bit inconvenient when trying to find the ignition switch in the dark...

again, many thanks, Peter

Hello Peter,

yes the plunger switches for the doors should be spring loaded.

Alec

Does anyone know where i can get hold of a pic or diagram that shows the location and fitment of these switches as my 420 has the wires but no switches fitted,cheers,H.

Same here... I have a feeling that should I find my way behind the front side interior panels, I'll find the wires for mine.

I'm assuming them to be fitted to the forward shut plate, like the rear ones, but a picture would be nice... hint, hint!

Hello Jackois,

the door switches are inside the hinge recesses and operated by the hinge itself.

Alec