# Full beam, horn, hazards, radio all not working



## 504329lt (Nov 6, 2006)

I have a 1994 Hymer 544 on a Ducato chassis.

When driving the other day, the following stopped working;

Full beam headlamps
Horn
Hazard Lights
Radio
Cigarette lighter
Fan

This has happened previously around six months ago but it righted itself, however this time I have driven around 400 miles since and everything is still not working.

Does anyone have any idea what could be wrong?

Thanks


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## lamperter (May 27, 2005)

I had a similar problem and it was found to be the fuse not sitting correctly in the holders, it is certainly worth a check as it is easily corrected


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## pjrenault (Aug 14, 2009)

*Hymer lost electrics*

Hello 504329lt (Fletcher by any chance  )
Help for your problem, (unless there's somebody here with knowledge of your vehicle who can then probably point you straight to the offending area) depends on a couple of things:
1) Do you have a wiring diagram and can you read it? If you haven't got one then you need one: owner's club, dealer or Ebay are possibilities.

2) Do you have either a test lamp or better still a voltmeter and do you know how to use it? If you can't use a testmeter or test lamp go straight to the advice at the bottom of this message.

3) You have checked all fuses to be intact and substituted any iffy looking ones with good new ones of the correct rating? 
Make sure they are the correct rating. My Renaults for instance have some fuses that have a different value on different variations of the vehicles, depending on what accessories are fitted. It can lead to fuses blowing after a prolonged period of use because they have soldiered on under just a little bit of overload. Also check the fuse for proper seating as the previous poster said, but also check the contacts are clean and bright on both the fuse and its holder. Clean with fine sandpaper or those nice green abrasive dish washing sponges if the memsahib isn't looking. If you find any fuses that have obviously died (particularly if it was violently) then you should trace the cause and DEFINITELY DO NOT increase the fuse value just to stop it blowing. Blown fuses are trying to tell you something!

After that here's a general guide as I don't claim any specific knowledge of your Hymer and its electrical circuitry: to lose all those services points to one of two possibilities: one or more failures in the wiring from the 12V supply to those devices or in the return to vehicle earth. Now it is possible that it could be multiple failures E.g. more than one blown fuse for instance, but that's much less likely than a single point of failure that is common to all those devices, esp as you seem to imply they all ceased to function at the same time.

Again I'm working without knowledge of your specific vehicle so I take it that when working correctly all the offending circuits should be available without the ignition key in or the ignition switched on?
They certainly are on my Renault trafic based vehicles.

Now for any electrical circuit to function the following needs to happen: there must be an electrically conducting path (usually a wire) from the voltage source (e.g a +12V point on the vehicle) to the device (usually a terminal on the device) and there must be an electrically conducting path back from the device to the other side (the negative) of the 12V supply. That return path to the negative side can be via direct contact from the device's case to the vehicle metalwork, or via a wire going to chassis or even sometimes routing direct back to the negative terminal on the battery on some vehicles (esp anything with a fibreglass body).

Nevertheless the same rule holds: from the positive voltage source, through an unbroken conducting path to the device then back from the device through an unbroken conducting path to the negative of the voltage source. Unfortunately modern manufacturers mess up this simple "wire to device, wire from device" idea because they tend to fit multiple connector plug/socket arrangements in the wiring of modern vehicles, so any plug/socket connector in that wire must also be checked for electrical and mechanical integrity too.

If we just set the circuit up like that it would work, but we couldn't control it: the device would be on forever. To stop it working we have to break the conducting path, by inserting a switch (or on many modern vehicles an electrically controlled switch called a relay) in the wire somewhere. Usually the "break" is put in the positive lead (as if the device's case is firmly in physical contact with the chassis/body metalwork we could hardly break into that negative return path). Judging from the number of devices you've got not working it is unlikely the fault is in the return side anyway.

More likely it is in the common feed that should be supplying the switches that control all the various devices. That's where your wiring diagram comes in. You need to identify where the +12V originates that feeds all those circuits. Look in your owner's manual (it should tell you which fuses feed all of the dead devices).

If it's a single fuse common to all of them then either +12V isn't reaching it (in which case you need to trace back along its feed wire to find the problem (broken wire, broken terminal, bad connector) or the +12V isn't leaving the fuse in which case it's a blown fuse, bad contact on the fuse socket or even a broken wire leaving the fuse connector. Two points:1) fuses can appear ok but actually have a tiny break in them (particularly at the ends) that is very difficult to spot: substitution with good and new is the best method and 2) when checking wires for mechanical soundness make sure you can actually see the wire end come under strain when you pull it. Many a fractured wire has been missed because the outer plastic sleeve was intact and hiding the fracture point as it was just before the bare end of the wire.

If there's more than one fuse involved then again you need to check for +12V arriving at each fuse. Almost certainly this time you'll find it isn't arriving and again you need to trace out the feed wire and find out where it ceases to provide +12V.

Note: I am disregarding the possibility that the 12V is failing to reach the devices because it is being short-circuited to chassis somewhere ahead of the common feed point, as you haven't mentioned anything about burnt wire, smoke and all other such excitement that usually accompanies short-circuits.

Hope that helps a bit.

If you're still stuck because electrical circuits are not your thing then I'd call in an autoelectrician or a buddy who does know about them, rather than simply play about: electrical gremlins could strand you at an inconvenient time, they could put you at the scene of a serious accident or they could even end up setting your vehicle on fire (and your garage etc if you park it under cover).


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## 504329lt (Nov 6, 2006)

Thanks for the replies.

I have checked all the fuses and all appear OK. I am trying to get hold of a wiring diagram.

The odd thing is that this was continually occurring when we were in France in December, but all the items mentioned would only go for a few minutes and then come back on.

Since then everything has been OK until last week although this time it seems to be more permanent. Although after parking up for 3 days, the horn did start to work again (very briefly!).


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## Jezport (Jun 19, 2008)

As a guess I would look for supply to the fuse box To start I would put a meter between the supply side to each of the fuses for the items not working and if the +ve supply is missing I would work back upstream. With so many items at fault I would suspect a big fuse in the engine bay fuse box which supplies many circuits is at fault (if it has one).

If the +ve supply is present at the fuses I would then check all the earthing points next.


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## sallytrafic (Jan 17, 2006)

All those services have one thing in common they require the ignition switch to be made so perhaps your are looking for a loose connection between that switch and any fuses, there may also be a super fuse or a relay that protects/controls all of those circuits.

I would have thought it highly illegal (IMHO) to drive a vehicle in that state.


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## Jezport (Jun 19, 2008)

sallytrafic said:


> All those services have one thing in common they require the ignition switch to be made so perhaps your are looking for a loose connection between that switch and any fuses, there may also be a super fuse or a relay that protects/controls all of those circuits.
> 
> I would have thought it highly illegal (IMHO) to drive a vehicle in that state.


Hazards are not through the ignition


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## emmbeedee (Oct 31, 2008)

sallytrafic said:


> All those services have one thing in common they require the ignition switch to be made so perhaps your are looking for a loose connection between that switch and any fuses, there may also be a super fuse or a relay that protects/controls all of those circuits.
> 
> I would have thought it highly illegal (IMHO) to drive a vehicle in that state.


I doubt the hazard lights require the ignition to be on. Normally they will work independently of the ignition. On some vehicles the horn will also work independently of the ignition.
Definitely agree about the illegality of using the vehicle though, the non-working horn alone makes it illegal.


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## sallytrafic (Jan 17, 2006)

emmbeedee said:


> sallytrafic said:
> 
> 
> > All those services have one thing in common they require the ignition switch to be made so perhaps your are looking for a loose connection between that switch and any fuses, there may also be a super fuse or a relay that protects/controls all of those circuits.
> ...


You are right,I read hazards thought indicators Doh!


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## raynipper (Aug 4, 2008)

I would first check the common earth points either side of the engine compartment chassis.

There is one below the horn and another below the battery. Either can get corroded and rusty. It's easy to dismantle and clean up the contacts as a first step.

Ray.


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## 504329lt (Nov 6, 2006)

emmbeedee said:


> sallytrafic said:
> 
> 
> > All those services have one thing in common they require the ignition switch to be made so perhaps your are looking for a loose connection between that switch and any fuses, there may also be a super fuse or a relay that protects/controls all of those circuits.
> ...


Horn / hazards / radio all work without ignition. Fan and headlights require ignition.


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## 504329lt (Nov 6, 2006)

Thanks for al the advice.

I have managed to get everyhting working by taking the dash off and fiddling with bunches of wires. Not sure what was loose but all OK now! Hope it stays that way.


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## aultymer (Jun 20, 2006)

> Not sure what was loose but all OK now! Hope it stays that way.


So next time it all goes off and it is dark/pissing down and you are 300 miles from home you will know how to fix it.
Enjoy!
But remember sod's law.


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