hi folks, someone out there has the answer to my question. why has the centre pin on my 12s plug melted? thanks in advance. geoff
12s centre pin
- Thread starter geoff_5040010
- Start date
Damian
Moderator
Geoff, the centre pin is the fridge earth return. To melt it would indicate a very heavy load causing excess heat to be generated, possibly by the incorrect size of wiring used on the return.
Its not unusual to have problems with the centre pin as it is the lead in when the plug is inserted and this causes the + in the cantre to close up and arcing then causes heat build up.
Its worth opening the + with a penknife from time to time.
I had the melting but have since doubled up on the earth to the fridge by using unused pins so that the load is shared between two .
Have a look on
www.towitall.co.uk
They describe the pins to be used
Its worth opening the + with a penknife from time to time.
I had the melting but have since doubled up on the earth to the fridge by using unused pins so that the load is shared between two .
Have a look on
www.towitall.co.uk
They describe the pins to be used
If there's a connection problem with pin 3, either in the car's 12S socket or the caravan's 12S plug then the battery charging / 12v permanent supply current earth will flow via caravan earth, pin 7, car earth. This will cause the centre pin, 7, to melt because it's overloaded.
Hi Roger
I never thought of it like that but it makes sense that if the centre pin is carrying the load of the fridge as well as the rest then it will be even more overloaded than just by the fridge return.
In my case the load from the fridge was sufficient but pairing the pins cured the problem
I always use substantially thicker wire than normal and have wired from the car battery earth to the 12N/S sockets as well.
I think that people experience trouble when on long tows (ie Spain ) when the fridge circuit is in use all day.
I had to do a rewiring job for a friend en route to Spain one time.
Regards John
I never thought of it like that but it makes sense that if the centre pin is carrying the load of the fridge as well as the rest then it will be even more overloaded than just by the fridge return.
In my case the load from the fridge was sufficient but pairing the pins cured the problem
I always use substantially thicker wire than normal and have wired from the car battery earth to the 12N/S sockets as well.
I think that people experience trouble when on long tows (ie Spain ) when the fridge circuit is in use all day.
I had to do a rewiring job for a friend en route to Spain one time.
Regards John
Hi,
The 12S centre pin is also used as a "entry guide" for joining the plug and socket - so it stands proud of all the other pins - and easily gets knocked, closing up the connector and causing a poor join / high resistance connection..
The fat copper pins in a 12N or 12S socket should easily handle 30 or more Amps - the reason they "melt" is solely due to poor connections causing a high resistance - and rapidly melt the plastic plug or the pin itself.
Once the connector is replaced - both sides of course - a regime of cleaning and contact maintenance needs to be followed - or it has the potential to degrade and melt again.
The solution is to use the Euro 13 pin plug and socket - this has been properly designed for use as a caravan connector - the connector body aligns the plug and socket not the pins - the pins are plated to prevent corrosion - the plug and socket are waterproof - the twist-lock action ensures a good connection - etc.
Robert
The 12S centre pin is also used as a "entry guide" for joining the plug and socket - so it stands proud of all the other pins - and easily gets knocked, closing up the connector and causing a poor join / high resistance connection..
The fat copper pins in a 12N or 12S socket should easily handle 30 or more Amps - the reason they "melt" is solely due to poor connections causing a high resistance - and rapidly melt the plastic plug or the pin itself.
Once the connector is replaced - both sides of course - a regime of cleaning and contact maintenance needs to be followed - or it has the potential to degrade and melt again.
The solution is to use the Euro 13 pin plug and socket - this has been properly designed for use as a caravan connector - the connector body aligns the plug and socket not the pins - the pins are plated to prevent corrosion - the plug and socket are waterproof - the twist-lock action ensures a good connection - etc.
Robert
found this for you,same as johns i think,
12s Pin Burn Out. Is There a Cure?
What Is The Problem?
Up to October 1997 and the introduction of new wiring standards for caravans and leisure vehicles, all the 12S system (with the exception of pin 1, yellow, reverse) relied on one heavy wire (pin 3, white) for the earth return. Pins 5 (brown) and 7 (black) were unused. Since EN1648-1, the central pin 7 (black) has been allocated as the refrigerator earth return and pin 2 (blue) is now redundant (previously battery charging circuit). These changes roughly coincide with the introduction of new larger fridge/freezers which, naturally, draw more current.
Pin 7 is an extended male segmented pin in the plug and acts as the 'lead' to guide the plug into the socket. As such, it is the one pin most likely to suffer damage in use. This, coupled with the higher current draw and the smaller cross sectional area of the wire is causing voltage drop, higher resistance, heat build up and consequently, melting plugs and/or sockets.
And The Answer?
You could change your double socket system on car and caravan to one of three continental 13 pin plug systems (either Jaeger or Feder/West Multicon). This, however, would entail changing other caravans and trailers that you may want to tow (though the Feder/West Multicon sockets will accept a standard 12N plug in the centre),and would prove expensive.
Alternatively, you could do a minor modification to the caravan 12S plug wiring. As pin 5 is unused, it is possible to link pin 7 to pin 5 and (provided the brown wire is earthed in the towing vehicle) share the load between both. Additionally, as pin 2 is now unused (though still probably connected to the split charge relay) the same can be done with the feed by linking pin 6 to pin 2.
The advantages are obvious. The combination of 2 cores gives a greater CSA than called for in the legislation and the load (feed and return) is shared by 4 pins instead of two. There will be less voltage drop, less resistance and less heat build up. It is a relatively simple DIY alteration and is inexpensive.
I would recommend using 28/0.30 (17.5 amp) cable for the linking wires.
Tony Maris
Towbars & Trailers, Chesterfield 28/08/2001
The writer has been Proprietor of Towbars & Trailers (Chesterfield) for over 20 years and lectures on Towbar Installations and Trailer Maintenance to members of the industry. He is a Council Member of the NTTA, is a founder member of the 'Quality Secured' working group and is currently chair of the NTTA's I.T. working group. His company was the first in the UK to be accredited to the NTTA's 'Quality Secured' standard. Additionally, he was the founding Treasurer of the re-formed Chesterfield and District Small Business Club and is a D.O.T. and RYA certified Yachtmaster (Offshore).
Supplementary to the above, tests performed by students on the last 3 NTTA courses have produced an improvement in the voltage drop to the fridge of 1.1 volts when using the two links as described. Towbars & Trailers as a company have been earthing the brown wire (pin 5) on all our towbar fittings since late 2001 and implementing the alteration to our customers caravans at their request. There has not been a single repeat instance of pin burn at this time (5/1/2003).
Disclaimer
The information in this guide is as accurate as the writer is able to make it, however, no responsibility can be accepted for any inaccuracies which may be in the text. It is the responsibility of any person wishing to depend on the facts to check for themselves with original documentation or any updating regulations, instruments or changes in the law. Interpretation of the law is a matter for the courts.
Copyright 2001 Tony Maris.
Tony Maris.The writer has been Proprietor of Towbars & Trailers (Chesterfield) for over 20 years and lectures on Towbar Installations and Trailer Maintenance to members of the industry. His company was the first in the UK to be accredited to the NTTA's 'Quality Secured' standard.
Towbars & Trailers Davian Works, Storforth Lane Chesterfield S40 2TU Tel: 01246 202543 Fax: 01246 202543
12s Pin Burn Out. Is There a Cure?
What Is The Problem?
Up to October 1997 and the introduction of new wiring standards for caravans and leisure vehicles, all the 12S system (with the exception of pin 1, yellow, reverse) relied on one heavy wire (pin 3, white) for the earth return. Pins 5 (brown) and 7 (black) were unused. Since EN1648-1, the central pin 7 (black) has been allocated as the refrigerator earth return and pin 2 (blue) is now redundant (previously battery charging circuit). These changes roughly coincide with the introduction of new larger fridge/freezers which, naturally, draw more current.
Pin 7 is an extended male segmented pin in the plug and acts as the 'lead' to guide the plug into the socket. As such, it is the one pin most likely to suffer damage in use. This, coupled with the higher current draw and the smaller cross sectional area of the wire is causing voltage drop, higher resistance, heat build up and consequently, melting plugs and/or sockets.
And The Answer?
You could change your double socket system on car and caravan to one of three continental 13 pin plug systems (either Jaeger or Feder/West Multicon). This, however, would entail changing other caravans and trailers that you may want to tow (though the Feder/West Multicon sockets will accept a standard 12N plug in the centre),and would prove expensive.
Alternatively, you could do a minor modification to the caravan 12S plug wiring. As pin 5 is unused, it is possible to link pin 7 to pin 5 and (provided the brown wire is earthed in the towing vehicle) share the load between both. Additionally, as pin 2 is now unused (though still probably connected to the split charge relay) the same can be done with the feed by linking pin 6 to pin 2.
The advantages are obvious. The combination of 2 cores gives a greater CSA than called for in the legislation and the load (feed and return) is shared by 4 pins instead of two. There will be less voltage drop, less resistance and less heat build up. It is a relatively simple DIY alteration and is inexpensive.
I would recommend using 28/0.30 (17.5 amp) cable for the linking wires.
Tony Maris
Towbars & Trailers, Chesterfield 28/08/2001
The writer has been Proprietor of Towbars & Trailers (Chesterfield) for over 20 years and lectures on Towbar Installations and Trailer Maintenance to members of the industry. He is a Council Member of the NTTA, is a founder member of the 'Quality Secured' working group and is currently chair of the NTTA's I.T. working group. His company was the first in the UK to be accredited to the NTTA's 'Quality Secured' standard. Additionally, he was the founding Treasurer of the re-formed Chesterfield and District Small Business Club and is a D.O.T. and RYA certified Yachtmaster (Offshore).
Supplementary to the above, tests performed by students on the last 3 NTTA courses have produced an improvement in the voltage drop to the fridge of 1.1 volts when using the two links as described. Towbars & Trailers as a company have been earthing the brown wire (pin 5) on all our towbar fittings since late 2001 and implementing the alteration to our customers caravans at their request. There has not been a single repeat instance of pin burn at this time (5/1/2003).
Disclaimer
The information in this guide is as accurate as the writer is able to make it, however, no responsibility can be accepted for any inaccuracies which may be in the text. It is the responsibility of any person wishing to depend on the facts to check for themselves with original documentation or any updating regulations, instruments or changes in the law. Interpretation of the law is a matter for the courts.
Copyright 2001 Tony Maris.
Tony Maris.The writer has been Proprietor of Towbars & Trailers (Chesterfield) for over 20 years and lectures on Towbar Installations and Trailer Maintenance to members of the industry. His company was the first in the UK to be accredited to the NTTA's 'Quality Secured' standard.
Towbars & Trailers Davian Works, Storforth Lane Chesterfield S40 2TU Tel: 01246 202543 Fax: 01246 202543
Hi Michael
That's the one
As far as changing to the 13pin superior system is concerned I will do that after Christmas.
Now where did I put that sledgehammer?
There may be some nuts to crack
That's the one
As far as changing to the 13pin superior system is concerned I will do that after Christmas.
Now where did I put that sledgehammer?
There may be some nuts to crack
There were never any problems with Pin 3 melting when it was the only -ve feed to the car and shared the return of both the fridge and the battery charger. Its got to be due to a high resistance in the Pin 7 plug and socket connection - the pin is obviously not a snug fit in the socket.
Is it possible to answer this question in simple terms please
I have a new lunar quasar and it is giving me problems re charging the fridge. I am now told by my dealer the fridge will not work on 12volts unless the battery is fully charged so i have to bring it home or drive to a site and hook up.
So if i collect it from storage and went to a c l without a hookup the battery would never get charged and the fridge wouln't work?
I understand about adding an extra earth wire as on our recent trip to spain the fridge stopped working and i had to keep opening up the middle pin every time we reconnected
Sorry to ramble
I have a new lunar quasar and it is giving me problems re charging the fridge. I am now told by my dealer the fridge will not work on 12volts unless the battery is fully charged so i have to bring it home or drive to a site and hook up.
So if i collect it from storage and went to a c l without a hookup the battery would never get charged and the fridge wouln't work?
I understand about adding an extra earth wire as on our recent trip to spain the fridge stopped working and i had to keep opening up the middle pin every time we reconnected
Sorry to ramble
Hi geoff
The state of charge of the caravan leisure battery should have no bearing on the fridge on 12V as it only works on 12V via the car battery when on tow.
The leisure battery is only needed for the fridge interior light and the gas igniter if its electronic rather than a pinger !!
The state of charge of the caravan leisure battery should have no bearing on the fridge on 12V as it only works on 12V via the car battery when on tow.
The leisure battery is only needed for the fridge interior light and the gas igniter if its electronic rather than a pinger !!
Thanks John
The fridge manual states the it will not work unless the battery is fully charged So I tried phoning Lunar customer service and they said their electrican would ring but he didn't.
I am now charging the battery to see if the fridge will work when it is fully charged it didn't today after collecing from dealer
How are you suppose to know if its charging when the fridge light is flashing?
Is this progress?
The fridge manual states the it will not work unless the battery is fully charged So I tried phoning Lunar customer service and they said their electrican would ring but he didn't.
I am now charging the battery to see if the fridge will work when it is fully charged it didn't today after collecing from dealer
How are you suppose to know if its charging when the fridge light is flashing?
Is this progress?
Geoff are you trying to work the fridge on gas and it won't ignite?
If you are trying to use it on 12V you will have a long wait as it is only used on 12V when the car engine is running and the alternator is operating.
The 12V operation takes about 12amps which would soon flatten a leisure battery
What make/model is your fridge?
If you are trying to use it on 12V you will have a long wait as it is only used on 12V when the car engine is running and the alternator is operating.
The 12V operation takes about 12amps which would soon flatten a leisure battery
What make/model is your fridge?
Hi again Geoff I looked on the Lunar website and it lists the Dometic 7 series
Have look here for your model
http://www.dometic.com/templates/ProductCategory.aspx?id=424
Have look here for your model
http://www.dometic.com/templates/ProductCategory.aspx?id=424
Hi John
No mines is fitted with the thetford one with manual changeover
it works fine on 240volt and gas the problem is only with 12volt
sometimes it will work and sometimes not. The dealer states that untill the battery is fully charged this is ok I will check later today when the battery has been on charge fo 24hrs and report back
Thanks for the input
No mines is fitted with the thetford one with manual changeover
it works fine on 240volt and gas the problem is only with 12volt
sometimes it will work and sometimes not. The dealer states that untill the battery is fully charged this is ok I will check later today when the battery has been on charge fo 24hrs and report back
Thanks for the input
Geoff to repeat the fridge is not designed to work on 12V except when the van is hooked up to the car and the engine running.
If the light is flickering when the engine is running then the problem is most likely with the 12V relay in the car.
If its voltage sensing it may need adjusting or replacing.
You could try getting someone to increase the engine revs slightly to see if the light stays on .
Hope that helps
If the light is flickering when the engine is running then the problem is most likely with the 12V relay in the car.
If its voltage sensing it may need adjusting or replacing.
You could try getting someone to increase the engine revs slightly to see if the light stays on .
Hope that helps
Hi john
just an update van been on charge for 24hrs now went out and connected up fridge works fine first time
So it appears that the book is right only works with a fully charged battery.
think this a step backwards
Still waiting for a phone call from lunar customer services
Hi john
just an update van been on charge for 24hrs now went out and connected up fridge works fine first time
So it appears that the book is right only works with a fully charged battery.
think this a step backwards
Still waiting for a phone call from lunar customer services
when i took the van back to the storage place this afternoon the fridge wouldn't work
So back to square one going to leave till after chritmas now
thanks all
just an update van been on charge for 24hrs now went out and connected up fridge works fine first time
So it appears that the book is right only works with a fully charged battery.
think this a step backwards
Still waiting for a phone call from lunar customer services
when i took the van back to the storage place this afternoon the fridge wouldn't work
So back to square one going to leave till after chritmas now
thanks all
Geoff I hope that you get it sorted.
I can't see how a fully charged or not leisure battery can affect the running of the fridge on 12V when it draws the 12V from the car battery.
Also when you use the 12V to the fridge from the car this activates the caravan habitation relay which cuts all power from the leisure battery on tow.
You can verify this by putting the caravan interior lights on and starting the car engine.They should go out as the habitation relay cuts off the power from the leisure battery.
I still think that your problem lies in the car wiring relay or connections
Do you have scotchlocks ?
I can't see how a fully charged or not leisure battery can affect the running of the fridge on 12V when it draws the 12V from the car battery.
Also when you use the 12V to the fridge from the car this activates the caravan habitation relay which cuts all power from the leisure battery on tow.
You can verify this by putting the caravan interior lights on and starting the car engine.They should go out as the habitation relay cuts off the power from the leisure battery.
I still think that your problem lies in the car wiring relay or connections
Do you have scotchlocks ?
Hi John
Thanks for the tip about the light
The van in storage and I will get it out and try again in january
I don't understand about the fully charged battery ideal either
But as I am still waiting for Lunars Electrian to ring I will report back later
Have a merry christmas everyone
Thanks for the tip about the light
The van in storage and I will get it out and try again in january
I don't understand about the fully charged battery ideal either
But as I am still waiting for Lunars Electrian to ring I will report back later
Have a merry christmas everyone
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