12s plug centre pin

Mar 14, 2005
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my 12s plug centre pin has overheated and melted the casing, on my way back from scotland this was the first time ive been able to get the fridge to work off 12v any ideas what has caused it before i replace the plug on the van as its out of shape and took a lot of effotr to get the pins to align. thanks for any help.
 
Mar 14, 2005
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David, this is a common problem. Pin 7, the centre pin, is the -ve return for the fridge cct (post 99 convention). There can only be one reason for heat and that is a high resistance. Check that the pin is a snug fit in the socketand spread it if neccessary. Make sure that the black wire on pin 7 is a good contact in both plug and socket and ensure that in the car it is going to a good earth.
 
Mar 14, 2005
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This indeed a very common problem due to the load on the fridge earth return.

Have a look on www.towitall.co.uk under trailer wiring. They tell how to use spare terminals in the plugsocketto share the load.I have done this with no further problems
 
Mar 14, 2005
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This indeed a very common problem due to the load on the fridge earth return.

Have a look on www.towitall.co.uk under trailer wiring. They tell how to use spare terminals in the plugsocketto share the load.I have done this with no further problems
John, it's very strange that this did not seem to happen on the pre 99 convention when the supply was on pin 2 with return on pin 3. It's also strange that it is only happening on the return pin 7 and not the feed on pin 6 on post 99 convention. It has got to be the centre pin that is not making good contact for whatever reason. What are your thoughts?
 
Mar 14, 2005
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This indeed a very common problem due to the load on the fridge earth return.

Have a look on www.towitall.co.uk under trailer wiring. They tell how to use spare terminals in the plugsocketto share the load.I have done this with no further problems
Ray I don't have a definate answer but some factors could be .

Fridges have got bigger and could be drawing more current

The centre pin being the lead pin is more likely to be squashed and this could cause arcing and heat build up.I wonder if swapping the fridge earth with pin 3 would improve matters.

Certainly linking pin7 with pin5 and pin 6 with pin2 on post 96ish vans has worked for me (ie ones with habitation relay)

I have always used heavier cable than standard to wire the 12 S socket with good earth connection so that is ruled out of the problem for me.The quality of the materials used in the 12S plug could possibly be better heat reistant .When mine went the plastic melted.Another BIG factor is length of tow.Towing to Spain on a hot day means that the fridge is on for hours via the 12S. Hope that helps
 
Mar 14, 2005
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Ray I don't have a definate answer but some factors could be .

Fridges have got bigger and could be drawing more current

The centre pin being the lead pin is more likely to be squashed and this could cause arcing and heat build up.I wonder if swapping the fridge earth with pin 3 would improve matters.

Certainly linking pin7 with pin5 and pin 6 with pin2 on post 96ish vans has worked for me (ie ones with habitation relay)

I have always used heavier cable than standard to wire the 12 S socket with good earth connection so that is ruled out of the problem for me.The quality of the materials used in the 12S plug could possibly be better heat reistant .When mine went the plastic melted.Another BIG factor is length of tow.Towing to Spain on a hot day means that the fridge is on for hours via the 12S. Hope that helps
I note that David was towing back from Scotland probably a long tow and more time for heat buid up to cause the problem perhaps
 
Mar 14, 2005
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Good advice to change the plug and socket

In practice the plug would have to be replaced but strangely the numerous ones I've seen on rallies etc only the plug has been affected and not the socket.This again raises doubts about the quality of the 12S plug plastic.

I wonder if anyone has had the same problem with the metal bodied 12S plug.The plastic between the pins is a different colour so could perform better ?
 

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