Tow Bar Electrics 7 or 13 pin plug

Fascinating...

Really?

Yes - there was a practical standard for a 12V live pin - pin 2, instead of the fog light which not many people had in any shape or form in the 70s.

All the cars that I have owned have the left and right side tail/side-lights separately fused and a single fuse for the brake-lights. Trailer wiring matches that.

Steve W

NY presented the following explanation :

There were two specs for the 12N. The later one has no provision for a

The original 12v supply on the 12N wasn't intended to supply such a heavy load as a fridge, but back then the standard wasn't really much of a standard. You would tend to have to test how car and caravan had been wired and make adjustments. Often a relay would be used, operated by the charge warning light, to switch that 12v power.

Modern fridges are able to operate from gas, 240v, or 12v when on the move. The 12v is not nearly as effective as the gas or 240v - usually they can just about hold the temperature down enough to cope.

Tim Watts used his keyboard to write :

They were very effective and more effective I think, than the modern coupling with built in friction.

Back in the late 70s/early 80s there was a plug and socket available (possibly 13-pin, but I can't remember) that had the same round pins as the normal 7-pin 12N, with additional flat pins around the outside edge. This was a far better system than the current one, as it gave all the extra connections required, while still allowing a 7-pin, 12N trailer plug to be plugged in, ignoring all the extra connections where they were no required - no adapters required.

SteveW

As I said earlier it's a requirement in some countries - or was. Namely Germany. Hence German made cars having it - even those made in RHD. All my BMWs had, and so does my present Porsche. The large Fords at one time were only made in Germany.

Eh? Piss easy with switches and relays (fixed pitch font required):

Ind SW o--- Left +---------+

LHS ommited for clarity but just has the relay with its NO and NC contacts paralled with the RHS relay and common to the LHS brake light. All switching is SPDT, (center off for the indicator switch...).

Rest: All open circuit, no lights on.

Brake: Circuit via NO brake switch and NC relays to brake lights. Brake lights on until brake switch is no longer made.

Indicate: Current flows through flasher and relevant side front bulbs they light and the relay energises causing the same side brake light to come on via the brake light switch NC and relay NO. The thermo electric flasher unit regularly interupts the +V causing all the relevant sides lights to flash together.

Indicate & Brake: As above except the relay energising switches the brake light off. The relevant sides front and back lights flash in anti phase. The other side brake light stays on via brake switch NO and that sides NC relay contact.

Simples.

I found it rather difficult to be sure. The requirements in Germany read much the same as in the UK: Vehicles and trailers parked on the road at night must be lit, with an exemption for vehicles (but not trailers) parked in a marked parking bay or on the road and adequately lit by street lighting. However, it is unclear from the sites I could find whether the German regulations permit the use of a single light, while the UK regulations definitely do not.

There are enough stupid people out there to ensure that it will happen on a regular basis and it does!

Ignition off, all lights set to off. Hold indicator stalk in appropriate position for side wanted for a second or two. An illuminated P with light "Rays" appears in the multifunction display in the rev counter to confirm.

That's how it is on an R56 registered in Dec 11.

G.Harman

Ah - thank you :)

It's interesting that cars are still being designed with this feature if it's no longer to park with only one front and back light showing in places where you need to use parking lights. I bet a lot of people think "if the feature is there, it must be legal to use it".

Strange that I've never been aware of it in any of the cars I've owned (Renault 5 Mark 1 and 2, VW Golf Mark 2 and 3, Peugeot 306 and 308). Maybe I've just not read the instruction manuals in sufficient detail, because it's never been something that I've thought to look for :-)

As I said, all my German made cars have this. Switch off the engine and lights. Move the indicator to the right, and only the right hand side light and tail light come on. Similarly with the indictor to the left. Which says to me this is or was a requirement in Germany. Of course at one time in the UK you needed parking lights too.

I really can't see any car maker designing it in if no longer needed anywhere? I've used the feature in the UK too. May not be needed, but may just make the car more visible.

Perhaps the really large quantities of non German spec VWs made meant it made sense to save the few extra pennies.

You still do!

Not in a 30mph or less limit if you are parked in the direction of traffic flow. Way back that wasn't the case but an often used accessory was a clip on light that showed white to the front and red to the rear that was clipped to the rain gutter of the car on the offside and roughly in the middle as required. This meant only the load of one lamp being taken from the battery, and even if the battery went a bit too flat to start most cars of that era had a starting handle. As cars progressed the manufacturers built the ability to leave the off side lamps on for parking, two lamps now but batteries and charging systems had progressed. Meanwhile our law changed so you don't actually have to use any lamps in 30 limits, but I occasionally use the parking lamp facility as a belt and braces , 30 mph limit ,no pavements, no street lighting narrow single track lane with field hedge on other side and slight bend. 99.9% of the time our vehicles are off road completely but occasionally we have to shuttle to get a visitor in and park on the edge for a bit. Dark Winter evenings are the most dangerous from about 15.00 , School run time

G.Harman

My father had one with an electromagnet to hold it on the car body. Fine when there were steel bodied cars