Cigarette lighter voltage too high (?) - how can I fix it?

[Mercmartin]

Whenever I plug in a mobile phone charger into the cigarette lighter socket of my K-reg W124 320 TE, it (the charger) blows immediately. I've destroyed three so far... I have measured the voltage to 13.4 V, whereas I understand it should be 12 V. This was measured with a number of lights/fans going at the same time. I have had no other problems with the electrics whatsoever and none of the fuses in the box under the bonnet is blown.

I'd be very grateful for any thoughts on what might be wrong and advice on how I can fix this - I need to be able to charge my mobile on longer trips as it runs the sat nav!

Thanks.

 

[television]

Whenever I plug in a mobile phone charger into the cigarette lighter socket of my K-reg W124 320 TE, it (the charger) blows immediately. I've destroyed three so far... I have measured the voltage to 13.4 V, whereas I understand it should be 12 V. This was measured with a number of lights/fans going at the same time. I have had no other problems with the electrics whatsoever and none of the fuses in the box under the bonnet is blown.

I'd be very grateful for any thoughts on what might be wrong and advice on how I can fix this - I need to be able to charge my mobile on longer trips as it runs the sat nav!

Thanks.

Hi Martin, all cars run at 13.8 volt negative earth since the 60's. The fault must be with the phone charger, may they are reversed polarity incorrectly built, it does happen

 

[television]

A phone charger is not suitable for SAT NAV as they consume in the order of 3 amps

 

[peter nicholls]

The voltage you are reading is correct it can go to 14.2 volts depending on how good your alternator is and what load is being drawn from the battery:roll:
have you checked that the voltage is the correct way in the lighter socket IE positive in the middle and not on the outside surface? .The two pin plug which connects the power could be the wrong way round hope this helps

 

[Mercmartin]

Ah... thanks for this Malcom, much appreciated! The weird thing is that the chargers were all different brands and indeed the cigarette lighter socket variety but marked "input 12V"... And the one I blew I had previosuly used without problem in another car. Not terribly clued up on electrics, but could it be some other problem with the car electrics, rather than the voltage?

 

[Mercmartin]

The voltage you are reading is correct it can go to 14.2 volts depending on how good your alternator is and what load is being drawn from the battery:roll:
have you checked that the voltage is the correct way in the lighter socket IE positive in the middle and not on the outside surface? .The two pin plug which connects the power could be the wrong way round hope this helps

Will check - thanks for the advice!

 

[television]

Ah... thanks for this Malcom, much appreciated! The weird thing is that the chargers were all different brands and indeed the cigarette lighter socket variety but marked "input 12V"... And the one I blew I had previosuly used without problem in another car. Not terribly clued up on electrics, but could it be some other problem with the car electrics, rather than the voltage?

Martin, your radio is on the same fuse line as the cigar lighter, any fault would take the radio out. I do not know and cant think of any other fault that could possibly do this

 

[Parrot of Doom]

The charger should contain a regulator anyway, many devices do not require 12V, some require only 4-6V. I can't see voltage blowing anything up there.

I'd check the polarity as Malcolm has suggested, someone may have wired it incorrectly.

 

[Mercmartin]

Checked the polarity and it is indeed wrong. Will correct this and with that hopefully the charger problems. Many thanks to all for sharing your knowledge!