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UK Caravanning (uk.rec.caravanning) A forum for the discussion of caravanning undertaken by residents of the United Kingdom, whether in the UK or abroad. It encourages the interchange of views on the merits of models of caravan, makes of tow car, accessories, caravan sites, caravan clubs, and other related topics. The term caravan is to include trailer vans, motor caravans and trailer tents.

Wiring



 
 
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  #1 (permalink)  
Old July 7th 03, 06:43 PM posted to uk.rec.caravanning
Paul Cohen
external usenet poster
 
Posts: 50
Default Wiring


Can someone please do a sanity check for me?

I've been analysing the wiring on the 12S plug, and I surmise it must be
functionally thus:

The voltage sensing doo-dah has four wires:

Black - permanent live input;
White - Earth;
Green - Permanent live output
Purple - Live when voltage high.

Three relays are then fed, their triggers coming from the Purple wire, and
the main feed to them from the Green wire - does that sound about right
please?

Thanks.

Paul C.


  #2 (permalink)  
Old July 7th 03, 08:30 PM posted to uk.rec.caravanning
David Thornber
external usenet poster
 
Posts: 47
Default Wiring

In message , Paul
Cohen writes

Can someone please do a sanity check for me?

I've been analysing the wiring on the 12S plug, and I surmise it must be
functionally thus:

The voltage sensing doo-dah has four wires:

Black - permanent live input;
White - Earth;
Green - Permanent live output
Purple - Live when voltage high.

Three relays are then fed, their triggers coming from the Purple wire, and
the main feed to them from the Green wire - does that sound about right
please?

It sounds like a convoluted, although probably perfectly effective way
of wiring the thing up. I'm not entirely sure why you would need three
relays, as only two outputs (battery charge and fridge) need to be
switched, even on the older wiring standard. The more recent standard
only needs the fridge supply to be switched by the engine - it sounds to
me like your split charge relay was designed to feed this later
standard, and the extra relays have been used to make the car compatible
with an older caravan's requirement for a separate switched battery
charge supply. On later caravans, this is handled by a relay inside the
'van that connects the battery to the permanent live feed from the car
when it senses that there is power to the fridge.

If you can work out which pins the relays output to, it would shed a
little more light on the matter.

--
David Thornber
  #3 (permalink)  
Old July 7th 03, 09:22 PM posted to uk.rec.caravanning
Tony Maris
external usenet poster
 
Posts: 161
Default Wiring

Hello Paul,

Your interpretation of the voltage sensing doo-dah wiring is correct as
stated by the manufacturer. However, it can be significantly improved. You
will note the wires are rather thin. Additionally, there is voltage drop
through the doo-dah.

If I were you, I would run a separate thick power feed to the relay(s) (pin
30), and a thinner wire from the battery to the doo-dah just to sense
battery voltage. Forget using the thin green to power the relay(s).

Question. Why use three relays? Pin 4 should be p.live on all 12S systems.
On post 98 only pin 6 needs to be voltage controlled. On pre 98, both pin 6
and pin 2 need to be voltage controlled.

If switching a normally open 4 pin relay, run heavy wire to pin 30, purple
to 85, earth 86, 12S red (and/or blue on pre 98) to 87. If switching a 6
pin relay, run heavy live feed to 21, 12S green to it's mate alongside
(forgot the number), 12S red to 14, 12S blue to 11, purple to [a] and earth
[b].

In any event, just tape up the thin green from the doo-dah.

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers



"Paul Cohen" wrote in message
.uk...

Can someone please do a sanity check for me?

I've been analysing the wiring on the 12S plug, and I surmise it must be
functionally thus:

The voltage sensing doo-dah has four wires:

Black - permanent live input;
White - Earth;
Green - Permanent live output
Purple - Live when voltage high.

Three relays are then fed, their triggers coming from the Purple wire, and
the main feed to them from the Green wire - does that sound about right
please?

Thanks.

Paul C.




  #5 (permalink)  
Old July 9th 03, 09:40 PM posted to uk.rec.caravanning
Tony Maris
external usenet poster
 
Posts: 161
Default Wiring

Hi Paul,

The legislation was dated October 1997 and some UK manufacturers anticipated
it so it is possible to find some late 1997, early 1998 vans wired to it.
However, it appears a number of 1998 models were still the old standard.
The giveaway would normally be whether on not the fridge earths back through
the black (no 7 pin) or white (no 3 pin).

Because of the increase in cable sizes, most manufacturers went on to 5 core
cable (no blue or brown). With this, they introduced a changeover relay in
the caravan. Whilst not voltage sensing in the sense of the electronic
split relays in common use, it does wait for a voltage to be applied to the
fridge feed. (Note, the fridge does not need to be on, it is sufficient for
voltage to be there). Once a voltage is picked up, the changeover relay
changes the function of no 4 pin from permanent live (int. lights etc) to
battery charging. This is done through the green wire.

The changeover relay AFAIK is peculiar to UK vans. If the grey cable in the
12S plug is 5 core, it will definitely have the relay.

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers



"Paul Westwell" wrote in message
...
Tony,

Sorry... another question for you...

I was familiar with the electrics on my pre 1998 van and as such have a
permanent live and two witched live feeds to my 12S socket. I ma about to
pick up a posy 1998 van and was interested to note the change you mention
whereby the charging circuit no longer has to be switched.

What have they changed to allow this to be the case, is the voltage

sensing
now done at the van end and does that apply to all post 98 vans?

Regards,

Paul


"Tony Maris" wrote in message
...
Hello Paul,

Your interpretation of the voltage sensing doo-dah wiring is correct as
stated by the manufacturer. However, it can be significantly improved.

You
will note the wires are rather thin. Additionally, there is voltage

drop
through the doo-dah.

If I were you, I would run a separate thick power feed to the relay(s)

(pin
30), and a thinner wire from the battery to the doo-dah just to sense
battery voltage. Forget using the thin green to power the relay(s).

Question. Why use three relays? Pin 4 should be p.live on all 12S

systems.
On post 98 only pin 6 needs to be voltage controlled. On pre 98, both

pin
6
and pin 2 need to be voltage controlled.

If switching a normally open 4 pin relay, run heavy wire to pin 30,

purple
to 85, earth 86, 12S red (and/or blue on pre 98) to 87. If switching a

6
pin relay, run heavy live feed to 21, 12S green to it's mate alongside
(forgot the number), 12S red to 14, 12S blue to 11, purple to [a] and

earth
[b].

In any event, just tape up the thin green from the doo-dah.

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers





  #6 (permalink)  
Old July 10th 03, 09:54 PM posted to uk.rec.caravanning
Paul Westwell
external usenet poster
 
Posts: 76
Default Wiring

Tony, thanks for that....

Just to clarify as I don't have a diagram at the moment.

Are only two 12V feeds required now, one switched for the fridge on pin 6,
and one permanent on pin 4 which supplies caravan lighting and is also
switched via a relay in the caravan for battery charging. The trigger for
this really is effectively the fridge wire on pin 6 going high?

Just trying to think if I need change my pre 98 vehicle wiring in any way
for a post 98 caravan? They only thing I can see is that the heavy duty
switched supply to pin 2 previously for battery charging in now redundant?
If I parallel what used to go to pin 2 to pin 6 then I will have a parallel
switched feed and less voltage drop....

Regards,

Paul

"Tony Maris" wrote in message
...
Hi Paul,

The legislation was dated October 1997 and some UK manufacturers

anticipated
it so it is possible to find some late 1997, early 1998 vans wired to it.
However, it appears a number of 1998 models were still the old standard.
The giveaway would normally be whether on not the fridge earths back

through
the black (no 7 pin) or white (no 3 pin).

Because of the increase in cable sizes, most manufacturers went on to 5

core
cable (no blue or brown). With this, they introduced a changeover relay

in
the caravan. Whilst not voltage sensing in the sense of the electronic
split relays in common use, it does wait for a voltage to be applied to

the
fridge feed. (Note, the fridge does not need to be on, it is sufficient

for
voltage to be there). Once a voltage is picked up, the changeover relay
changes the function of no 4 pin from permanent live (int. lights etc) to
battery charging. This is done through the green wire.

The changeover relay AFAIK is peculiar to UK vans. If the grey cable in

the
12S plug is 5 core, it will definitely have the relay.

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers



"Paul Westwell" wrote in message
...
Tony,

Sorry... another question for you...

I was familiar with the electrics on my pre 1998 van and as such have a
permanent live and two witched live feeds to my 12S socket. I ma about

to
pick up a posy 1998 van and was interested to note the change you

mention
whereby the charging circuit no longer has to be switched.

What have they changed to allow this to be the case, is the voltage

sensing
now done at the van end and does that apply to all post 98 vans?

Regards,

Paul


"Tony Maris" wrote in message
...
Hello Paul,

Your interpretation of the voltage sensing doo-dah wiring is correct

as
stated by the manufacturer. However, it can be significantly

improved.
You
will note the wires are rather thin. Additionally, there is voltage

drop
through the doo-dah.

If I were you, I would run a separate thick power feed to the relay(s)

(pin
30), and a thinner wire from the battery to the doo-dah just to sense
battery voltage. Forget using the thin green to power the relay(s).

Question. Why use three relays? Pin 4 should be p.live on all 12S

systems.
On post 98 only pin 6 needs to be voltage controlled. On pre 98, both

pin
6
and pin 2 need to be voltage controlled.

If switching a normally open 4 pin relay, run heavy wire to pin 30,

purple
to 85, earth 86, 12S red (and/or blue on pre 98) to 87. If switching

a
6
pin relay, run heavy live feed to 21, 12S green to it's mate alongside
(forgot the number), 12S red to 14, 12S blue to 11, purple to [a] and

earth
[b].

In any event, just tape up the thin green from the doo-dah.

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers







  #7 (permalink)  
Old July 10th 03, 10:42 PM posted to uk.rec.caravanning
Tony Maris
external usenet poster
 
Posts: 161
Default Wiring

Hello Paul,

You've got it!

One thing you will need to do is earth the black wire (pin 7) in your
vehicle's 12S if it hasn't already been done. Doubling up on the power feed
to reduce voltage drop is a sensible idea.

I was running a training course yesterday and the only time the students
managed to get 12 volts to the 'fridge' was after doubling up on the fridge
earth and live feeds, reverting to a mechanical relay with a voltage sensing
switcher and using 6 mm supply cable from the vehicle battery. This was on
a Saab 900 producing 14.2 volts at the battery whist a 19.2 amp load (Fridge
and battery charging) was being drawn.

For details on the doubling up procedure, have a look at
http://www.towitall.co.uk/faq/information.htm and read the 12S pin burn out
article.

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers



"Paul Westwell" wrote in message
...
Tony, thanks for that....

Just to clarify as I don't have a diagram at the moment.

Are only two 12V feeds required now, one switched for the fridge on pin 6,
and one permanent on pin 4 which supplies caravan lighting and is also
switched via a relay in the caravan for battery charging. The trigger for
this really is effectively the fridge wire on pin 6 going high?

Just trying to think if I need change my pre 98 vehicle wiring in any way
for a post 98 caravan? They only thing I can see is that the heavy duty
switched supply to pin 2 previously for battery charging in now redundant?
If I parallel what used to go to pin 2 to pin 6 then I will have a

parallel
switched feed and less voltage drop....

Regards,

Paul



  #9 (permalink)  
Old July 11th 03, 07:01 PM posted to uk.rec.caravanning
Paul Cohen
external usenet poster
 
Posts: 50
Default Wiring

In article ,
(Tony Maris) wrote:

One thing you will need to do is earth the black wire (pin 7) snip


I've now completed my 'works' and completely redone the wiring. I've
doubled up on the fridge feed (blue into red) as you suggested, but I
think even more importantly doubled up on the earth (earthed brown into
black) (which you also suggested). What really brought this home was when
I said to my wife "Right, I'm going to plug the caravan's 12S male in to
my nice new 12S socket. Remember how I used to struggle? Well watch how
easy it goes in now..." and then proceeded to struggle. I then had a
*good* look at the 12S male, and the plastic around pin 7 was a bit
melted. When I took the plug apart I could not believe how badly melted it
was! (I had to cut the black wire - there was no way it could be unscrewed
- and the wire end was badly corroded.)

Anyway, it now works lovely - fridge comes on when car is idling, so
resistance looks like it's low. I used 4mm wire for the battery charging
feed, and on idle that supplied 6A to a half-discharged battery, so that
wasn't too bad.

I'm glad I ordered a box load of crimps - I got through a fair few - I
changed my mind more than once!

And I'm really really glad I used a crimper - it was much quicker and much
stronger than soldering (and probably lower resistance too).

JAAMOI, I noticed that the caravan's 12S wire ends were tinned. I'm
surprised. It's not a good idea. Over time, the solder flows and the
connection loosens. Maybe Bailey didn't know that :-).

Paul C.


  #10 (permalink)  
Old July 11th 03, 07:34 PM posted to uk.rec.caravanning
Tony Maris
external usenet poster
 
Posts: 161
Default Wiring

Hi Paul,

Glad you've got it sorted. You should now have cured pin burn out for good.
With any luck, you might also get cool beer and non-runny butter!

On the pin burn out thing, some of the examples I've collected are truly
frightening. (I save them to show students on the NTTA Towbar Installations
course). One I have, the middle pin (earth) has displaced so much it is
literally within a whisker of sitting on no 4 pin (P. Live). There must
have been instances where these have touched, with the obvious result.

We now give a lifetime guarantee on our towbar electrics and I do not tin
the ends of the wires. I prefer instead to make sure the insulation is cut
back only slightly and the locating screw in the pins actually holds the
insulation rather bearing straight down on the copper. We also use grease
in the sockets as it appears impossible to prevent moisture ingress (or
condensation).

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers



"Paul Cohen" wrote in message
.uk...
I've now completed my 'works' and completely redone the wiring. I've
doubled up on the fridge feed (blue into red) as you suggested, but I
think even more importantly doubled up on the earth (earthed brown into
black) (which you also suggested). What really brought this home was when
I said to my wife "Right, I'm going to plug the caravan's 12S male in to
my nice new 12S socket. Remember how I used to struggle? Well watch how
easy it goes in now..." and then proceeded to struggle. I then had a
*good* look at the 12S male, and the plastic around pin 7 was a bit
melted. When I took the plug apart I could not believe how badly melted it
was! (I had to cut the black wire - there was no way it could be unscrewed
- and the wire end was badly corroded.)

Anyway, it now works lovely - fridge comes on when car is idling, so
resistance looks like it's low. I used 4mm wire for the battery charging
feed, and on idle that supplied 6A to a half-discharged battery, so that
wasn't too bad.

I'm glad I ordered a box load of crimps - I got through a fair few - I
changed my mind more than once!

And I'm really really glad I used a crimper - it was much quicker and much
stronger than soldering (and probably lower resistance too).

JAAMOI, I noticed that the caravan's 12S wire ends were tinned. I'm
surprised. It's not a good idea. Over time, the solder flows and the
connection loosens. Maybe Bailey didn't know that :-).

Paul C.




 



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