# help please 1992 Hymer 544 Lighting Wiring Fault



## thegreatpan (Oct 29, 2007)

Help,

The following bank of lights on my 1992 Hymer 544 MH are all fed from the same fuse; cab lights, above cab bed light and and the bench seat fluorescent. None of these have worked since I bought the van.

Today I have spent the day with multimeter and found out that all fuses are ok, I am getting 12.4 volts on the blue wire that feeds all these fittings(according to the wiring diagram). But worryingly I am also getting 11.6 volts on what should be the earth?

Please can someone tell me how I can get the earth to read voltage without blowing the fuse?

The Truma boiler etc works from the same fuse and is fine as it has a different earth path.

I removed the fluorescent and wired it to a spare battery and it works fine, I also did this with all the festoon bulbs from the cab lights and they are fine.

Any one tell me where to start


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## 101820 (Nov 17, 2006)

Hi

It puzzles me on how you measured 11.6v to earth. Which earth did you use? ie did you measure from one earth to another and as you would hope you should get 0V.

If you got 11.6v from earth to earth then yes some thing wrong.

If you connect these two earths together via a fuse and it blows then you have a partial short somewhere along the line.

I would disconnect the earth to the lights and connect another earth from somewhere else and see if that works.


David


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## sallytrafic (Jan 17, 2006)

Those are the classic symptoms of an earth fault. Wire isn't completely off otherwise you would have measured the same voltage both sides of your light fitting (a dvm draws so little current that there is no voltage drop across the device).


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## thegreatpan (Oct 29, 2007)

All voltages were read with the multimeter being earthed to the chassis via the clutch pedal?

Has me perplexed, I can only assume the earth has become insulated/broken from its normal return path to the battery negative and is picking up a live feed?

The wires run through the pull down bed,that is next on my list to check.

Any ideas anyone?


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## sallytrafic (Jan 17, 2006)

thegreatpan said:


> All voltages were read with the multimeter being earthed to the chassis via the clutch pedal?
> 
> Has me perplexed, I can only assume the earth has become insulated/broken from its normal return path to the battery negative and is picking up a live feed?
> 
> ...


No as I said before all that has happened is the earth has gone from the circuit. You don't have to have another live feed. The one that is connected to the lamp or whatever you are measuring is all you need to explain this fault.

Take the first lamp circuit shown below if you measured it at point A you would get zero volts if the other meter prod was atttached to earth.

The second circuit is the same as the first with a broken earth. If you measured at B you would get about 12V. If the earth was just badly corroded you might get a lesser voltage say 10V and indeed the lamp might show a glimmer.


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## JohnsCrossMotorHomes (Jul 21, 2007)

Hi,

If you can't get it sorted and as your in East Sussex, bring it in to us and we will have a look and see if we can sort it.

But as Gerald says it look like you have not got an decent earth, try putting a wire lead the other side of the lamp and earth it to the chassis somewhere.

Regards and good luck.

Peter


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## sallytrafic (Jan 17, 2006)

JohnsCrossMotorHomes said:


> Hi,
> 
> If you can't get it sorted and as your in East Sussex, bring it in to us and we will have a look and see if we can sort it.
> 
> ...


Gerald? (not that I mind being mistaken for the great Gerald  )

Any feedback thegreatpan?


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## thegreatpan (Oct 29, 2007)

Dear All,

Thanks for the suggestions so far, 

Frank(Gerald?) any more diagrams to help a numpty like me would be much appreciated.

Due to stropy neighbours and restrictive covenants, I have had to put the MH back into storage, as I am away on work this week, 

I am coming up to my duty weekends with days off mid-week where I will have another go with the mutimeter. I aim to trace all the wiring and label them, as the leisure battery area is a bit like spaghetti, due to all the extras that were fitted to the van by the previous owner.

What was bewildering was that all of the various light fittings that shared the common earth showed the same voltage on the earth wire, whether they were connected to the fitting, or removed and a reading was taken from the naked unconnected spade connector (using the chassis earth). Hence my reasoning for the system getting a feed on the earth side.

What would happen if I were to create a new earth for these lights?


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## sallytrafic (Jan 17, 2006)

thegreatpan said:


> Dear All,
> 
> Thanks for the suggestions so far,
> 
> ...


They would work!

In the circuit shown below all the lamps would not work but where ever you connected your multimeter prod A,B or C for example you would measure 12V (assuming the other prod was at earth).

In case A that shows the effect of measuring either at the lamp or at the unconnected earth lead - 12V just the same.


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## 108717 (Dec 12, 2007)

I have a full manual for 88/89 models which might be the same. Includes the full wiring diagram and in English. Too big to post to the files section but could send by other means. PM me if you fancy trying it. In PDF format and in 2 parts covering all models from those years.


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## thegreatpan (Oct 29, 2007)

I have today found the defective wire. When I looked at the van last week I assumed the wires ran forward to the leisure battery, when I reached a dead end there, I traced the wires back to the space under the wardrobe, where I found a connector with the spade terminal broken.

I replaced the terminal and everything works  

What I still can't work out, is that even though I had taken the live and earth wire off every fitting, I was still getting 12.4 volts on the earth wire when I provided a different path to earth (through the clutch pedal), does this mean I have a current drain?


Having also re-instated the blown air heating pipes today , all I now need is to find a washer to sort out a slight leak from the UK propane adaptor to the german regulator connection, make the Oyster digital sat TV find an English speaking channel and I will have everything up and running.


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