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I have an issue with 12v power to a socket. I have retired a socket and it no longer has power to it. Other 12v  sockets aok.

 

I have had a multimeter, pictured, for ages. I can never remember how to work the dammed thing. It’s a simple task but hey ho!

 

The black lead goes in the black socket. (I can work that one out),

First question where should the red one go for ascertaining power at end of cable. 
Where should the dial be set?

 

I realise this is very simple to some, but it’s me.

DEB504EC-99EA-43BD-9DF7-8A2EE937DB5D.jpeg

Edited by Nightwatch
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Just now, Nightwatch said:

I have an issue with 12v power to a socket. I have retired a socket and it no longer has power to it. Other 12v  sockets aok.

 

I have had a multimeter, pictured, for ages. I can never remember how to work the dammed thing. It’s a simple task but hey ho!

 

The black lead goes in the black socket. (I can work that one out),

First question where should the red one go for ascertaining power at end of cable. 
Where should the dial be set?

 

I realise this is very simple to some, but it’s me.

 

Look in the electrical notes on www.tb-training.co.uk

 

Its all there with images

 

 

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21 minutes ago, Nightwatch said:

I have an issue with 12v power to a socket. I have retired a socket and it no longer has power to it. Other 12v  sockets aok.

 

I have had a multimeter, pictured, for ages. I can never remember how to work the dammed thing. It’s a simple task but hey ho!

 

The black lead goes in the black socket. (I can work that one out),

First question where should the red one go for ascertaining power at end of cable. 
Where should the dial be set?

 

I realise this is very simple to some, but it’s me.

DEB504EC-99EA-43BD-9DF7-8A2EE937DB5D.jpeg

 

 

Red lead in the RH side red socket

Dial set to 20v on the 'yellow' (DC) scale (the scale it is on now but 'up-a-click')

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Got the socket working. If........I have the pos/neg incorrectly wired up will a table light work but blow the USB charger and the 12v connector to the telly?

Edited by Nightwatch
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10 minutes ago, Alan de Enfield said:

 

Yes

 

 

Yes

 

 

Maybe

Thank you for that. It’s what I feared. I am working in the saloon at the bow. The cables coming from the stern are both brown. One has a reddish line. I am presuming the reddish lined one is positive. (Only just seen the red bit after rubbing the cable with the wife’s wet finger.) H&S!

So I have to ‘assume’ I have the cables wrong way round.

In addition, the TV 12v connector adaptor had a blown fuse. Replaced fuse but still doesn’t work. Has it bu*gered the adaptor? Is it repairable. The USB multi socket charger does not have an accessible fuse as far as I can see. Is that irreparable?

Edited by Nightwatch
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1 minute ago, Nightwatch said:

Thank you for that. It’s what I feared. I am working in the saloon at the bow. The cables coming from the stern are both brown. One has a reddish line. I am presuming the reddish lined one is positive. (Only just seen the red bit after rubbing the cable with the wife’s wet finger.) H&S!

So I have to ‘assume’ I have the cables wrong way round.

 

Now you know why my notes suggested connecting the meter negative direct to the battery negative, or in most cases the hull will do. That way you find the positive when the meter shows a voltage so if that brownish wire is negative it would have sown zero when connected to the meter. You seemed to ask how to set the meter up, not how to use the meter to check cables and circuits.

  • Greenie 1
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6 minutes ago, Nightwatch said:

Thank you for that. It’s what I feared. I am working in the saloon at the bow. The cables coming from the stern are both brown. One has a reddish line. I am presuming the reddish lined one is positive. (Only just seen the red bit after rubbing the cable with the wife’s wet finger.) H&S!

So I have to ‘assume’ I have the cables wrong way round.

 

If you test them and get them the wrong way around (ie touch your + probe to the negative wire , and - probe to the postive wire) your meter should show a - sign (mine does)

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1 minute ago, Tony Brooks said:

 

Now you know why my notes suggested connecting the meter negative direct to the battery negative, or in most cases the hull will do. That way you find the positive when the meter shows a voltage so if that brownish wire is negative it would have sown zero when connected to the meter. You seemed to ask how to set the meter up, not how to use the meter to check cables and circuits.

Thank you.

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4 minutes ago, Alan de Enfield said:

 

If you test them and get them the wrong way around (ie touch your + probe to the negative wire , and - probe to the postive wire) your meter should show a - sign (mine does)

This type of socket. Red in top, black in bottom shows, engine running, 12.6. Volts. However, Red in bottom, black in top same voltage but with - sign.

 

Wired correctly or not.

F40A25DD-A816-4BB5-8DBD-29C9DF2D04BC.jpeg

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5 minutes ago, Nightwatch said:

This type of socket. Red in top, black in bottom shows, engine running, 12.6. Volts. However, Red in bottom, black in top same voltage but with - sign.

 

Wired correctly or not.

 

 

Modern multimeters do that to tell you have reversed the polarity/put the test probes the wrong way round. From what you say I would suggest that the top slot is positive and the bottom one negative.

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2 minutes ago, Tony Brooks said:

 

Modern multimeters do that to tell you have reversed the polarity/put the test probes the wrong way round.

Whereas old analogue multimeters tell you you have reversed the polarity by the needle slamming into the end stop to the left of the zero reading.

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16 minutes ago, Tony Brooks said:

From what you say I would suggest that the top slot is positive and the bottom one negative.

 

 

It would appear that somewhere in the wiring (between battery and socket your colours / polarity have been reversed

 

By convention it should be

Red / Positive /  Live and

Black / Negative / Neutral.

 

Live and neutral are not usually used in the Uk for 12v systems - are the sockets Chinese ?

 

There doesn't look to be any way to orientate the plug to ensure correct polarity** (it can go in either way) so whatever way you wire it up it could be incorrectly 'plugged in'.

 

 

 

Edit

 

* * is the bottom slot a fraction smaller than the top one so it cannot be reversed ?

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24 minutes ago, Tony Brooks said:

 

Modern multimeters do that to tell you have reversed the polarity/put the test probes the wrong way round. From what you say I would suggest that the top slot is positive and the bottom one negative.

My assumption also.

5 minutes ago, Alan de Enfield said:

 

 

It would appear that somewhere in the wiring (between battery and socket your colours / polarity have been reversed

 

By convention it should be

Red / Positive /  Live and

Black / Negative / Neutral.

 

Live and neutral are not usually used in the Uk for 12v systems - are the sockets Chinese ?

 

There doesn't look to be any way to orientate the plug to ensure correct polarity** (it can go in either way) so whatever way you wire it up it could be incorrectly 'plugged in'.

 

 

 

Edit

 

* * is the bottom slot a fraction smaller than the top one so it cannot be reversed ?

The bottom slot is slightly smaller.

  • Happy 1
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Thank you all for you suggestions and help I think I’ve done it. The usb charger is defunct as is the adaptor for the TV. There is power to the adaptor (light) but nowt coming through to the telly. Telly is now a mains only telly. I have bought a new USB charger and it works! Job done.

 

Electrics have always confused me as does terminology. My concentration is almost non existent. I may come across as stupid and flippant but I’m not always.

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I think you may have more of a problem if you have anything that plugs into those outlets. They seem to have been wired in reverse polarity but where is the issue. I expect that if you take the unit off the wall you will find its easy to simply swap the connections over on each socket so the + and - markings are correct but then you would need to do the same for any plugs that are used in those sockets. By doing that and checking any other sockets you minimise the chances of anyone damaging equipment in the future.

 

If you find the wire colours at the back of the socket seem wrong then the best thing to do is to work back until you find where  they have been transposed. It could be behind another socket closer to the fuse box.

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21 hours ago, Alan de Enfield said:

Dial set to 20v on the 'yellow' (DC) scale (the scale it is on now but 'up-a-click')


This is fine for what is expected to be a 12V system, but the more general guidance if one is not sure of the voltage, would be to start set at the maximum range (in this case 600V), and work down to a sensible. Perhaps this is a bit old fashioned and less of a problem with digital meters, it was very applicable to meters with moving needles.

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2 hours ago, Tony Brooks said:

I think you may have more of a problem if you have anything that plugs into those outlets. They seem to have been wired in reverse polarity but where is the issue. I expect that if you take the unit off the wall you will find its easy to simply swap the connections over on each socket so the + and - markings are correct but then you would need to do the same for any plugs that are used in those sockets. By doing that and checking any other sockets you minimise the chances of anyone damaging equipment in the future.

 

If you find the wire colours at the back of the socket seem wrong then the best thing to do is to work back until you find where  they have been transposed. It could be behind another socket closer to the fuse box.

Didn't he say they were both brown wires

 

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28 minutes ago, ditchcrawler said:

Didn't he say they were both brown wires

 

If so then I think at least one needs a bit of red sleeving on it at each outlet and the polarity of the sockets and any plugs he uses changing. At the moment its asking for damage to equipment.

 

 

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