Help needed please, lighting anomaly!!

[laimeduck]

I have been having problems with parasitic drain ever since I bought this van & have made various posts on this forum.

For various reasons that are immaterial, I had to stay in my motorhome last night. I had to get up to turn off an alarm at 05.45 & noticed that 2 of the 12V G4 LED spots over the sink were emitting a very slight glow, even though the switch(A) for these lights was off.

This morning I ran a series of checks and find that the glow from these 2 lights only occurs when the EHU is attached.

 

1)I have checked the switch & it operates correctly.

 

2)When the main 12V panel is on, there is a slight glow when the switch(A) is off.

 

3)When the main 12V panel is off, there is a slight glow when the switch(A) is off, but this glow stops when the switch(A) is turned on.

 

4)When I uncouple the EHU there is no glow in either position.

 

5)When I uncouple the EHU and charge the system with the engine running, there is no glow.

 

This leads me to believe that somehow there is current bypassing the switch(A) from the on-board battery charger(only works when EHU attached)(This is integral to the control panel)

 

HELP!!! :'( :'(

 

What other checks can I do? & what should I look for?

How can this happen when switch(A) is off? (I even took the switch off, disconnected the wires and still got a glow!)

I have managed to stop the drain by turning the main 12 Volt panel off, while leaving the Switch (A) in the “on” position.(as in 3) above)

(The bulbs are 12V G4 5050 SMD 9LED, recently bought)

The van is a 2004 build, 2005 registered Benima Perseo 710 CCX, 2.8 JTD Ducato

[Keithl]

Jeremy,

 

This sounds like the phenomenon whereby if you carry a fluorescent tube under power lines it will illuminate. In your case it is the current flowing in adjacent wires inducing a current in the wires to the LEDs. It has a technical name something like Induced EMF.

You can check whether it is the cause by taking the wire off the switch which goes to the LEDs and connecting it to the negative at this point. The glow should then disappear.

Another thing to check would be for voltage across this wire and negative under the conditions when the LEds are glowing.

 

If this is the correct diagnosis then the only solution I can think of at the moment would be to change the switch from a Single Pole Single Throw (SPST) to a SP Double Throw (SPDT) or 'changover' switch with the common connected to the LEDs and use this to connect the LED positive wire to negative when switched off. I hope this makes sesnse (it does to me :-D ).

 

Keith.

 

PS It would not have been noticeable with conventional bulbs as insufficient current would have been generated to illuminate the bulb.

[lennyhb]

I agree with Keith probably caused by spikes on the 12v lines from the switched mode power supply in the charger.

You could try looping the the 12v cables from the charger through some ferrite coils - something like this

[laimeduck]

Keithl - 2011-12-01 12:34 PM

 

You can check whether it is the cause by taking the wire off the switch which goes to the LEDs and connecting it to the negative at this point. The glow should then disappear.

Another thing to check would be for voltage across this wire and negative under the conditions when the LEds are glowing.

 

 

Keith.

 

PS It would not have been noticeable with conventional bulbs as insufficient current would have been generated to illuminate the bulb.

 

Keith & Lenny thanks for this.

Just a query though on the check you mention above.

Do you mean disconnect the wire on the LED side of Switch(A), then connect it to earth ( ie the negative of the 12V battery)?

If this is the cause of the glow, will it do any harm to the LED's or shall I simply ignore it? The glow is very faint - like the luminous glow from an old watch.

 

 

[Keithl]

laimeduck - 2011-12-01 5:28 PM

Do you mean disconnect the wire on the LED side of Switch(A), then connect it to earth ( ie the negative of the 12V battery)?

If this is the cause of the glow, will it do any harm to the LED's or shall I simply ignore it?

 

Yes that is correct, all you would then be doing is dissipating any voltage induced to negative and the LED's should then not glow.

I don't believe it will harm the LED's as you will not be applying any voltage to them, you will simply be connecting their positive and negative wires together.

 

Keith.

[Derek Uzzell]

This is a link to a thread about 'domestic' LED bulbs still glowing when switched off

 

http://www.candlepowerforums.com/vb/showthread.php?283847-LED-s-glow-when-off

 

I don't know how relevant the comments are to Jeremy's problem, but some (but not others) of the LED bulbs I've fitted to my own motorhome definitely have a capacitor in their circuitry.

[Brian Kirby]

Derek Uzzell - 2011-12-02 9:33 AM

 

This is a link to a thread about 'domestic' LED bulbs still glowing when switched off

 

http://www.candlepowerforums.com/vb/showthread.php?283847-LED-s-glow-when-off

 

I don't know how relevant the comments are to Jeremy's problem, but some (but not others) of the LED bulbs I've fitted to my own motorhome definitely have a capacitor in their circuitry.

Wonderful link, Derek! Streams of highly informed theorising, and then the killer! The chap who, after all the theories had been expounded, shot down the lot by revealing that his LEDs continued glowing even after they had been completely removed from the fitting! Priceless! :-D

 

For those disinclined to read the lot, he postulates a capacitor built into the LED lamp itself. Convinced me, but I have no idea if he is right.

[Keithl]

I have to agree that it is an excellent theory on an in-built capacitor, but unfortunately this is not the case for Jeremy as he can turn his glow on and off at will.

 

I still favour my original theory of induced voltage from other wiring and this follows the same logic as that given for 2-way switch wiring in the link.

 

I have recently replaced all the lighting (Halogen and Fluorecescent) with LEDs in our MH so will have to experiment to see if I can induce any glowing in the dark :D

 

Keith.

[BrianBW]

Only when the EHU is connected. If this Electrical Hook Up, then the problem could be due to the mains Earth cable attached to the chassis. This is an electrical necessity and often drops off due to corrosion and leakage current. If off, the leakage current is passing through the LED's. Hard to find but its there somewhere!

[Brambles]

Jeremy.

 

Try putting one of these, a 1uF non polarised capacitior

 

http://www.ebay.co.uk/itm/1UF-1MFD-250V-ASHCROFT-CAPACITIOR-1-PC-/350194057369?pt=UK_Consumer_VintageAudio_RL&hash=item5189314099

 

 

across the switch(A) contacts. This may and probably will cure your problem of the glowing lights.

 

If it does not work it is not a waste of money or time because it will help analyse where one is needed.

The other place is possibly going to be across one of the lights itself.

 

 

Trust me, I am a Doctor!!!!! No, serously I know what I am talking about as is my specialist area to cure electrical noise on vehicles. This solution is a bit of bandage rather than solving the problem at source but then that will be a lot harder and require a lot more investigation on your part. It is caused by the mains cables distributed around the vehicle being cross coupled onto the 12 volt wiring, or even conducted because of some earth loop, maybe at the fridge which has both 12 volt and 240 volt supplies connected.

 

The key to me suggesting it goes across the switch is because when you have the 12 volt panel off but the light switch on the glow stops. This is because you have connected the 12 volt feed up to the switch which also has noise induced on the cable. If you assume, simpistically, noise is induced on the ground lead to teh lights, but not on the positve feed then the light may glow and it does. So, by connecting the Positve with switch A you stop the glow because you have now injected noise to the lamp on both positive and negative. It is called common mode and the light sees no voltage across it.

By fitting the capcitor we are feeding noise from the positve up to the switch across onto the positve feed to lights by capacitively coupling it. The ac noise will go across the capacitor to other side but the dc will not. It is as if the switch is closed for the induced noise. What worries me though is when you switch the 12 volt panel on again there may be another path for the noise or will be a lot higher now on the 12 volt circuit. So fingers crossed it won't.

 

Basically rather than filter the noise or ground it, I am deliberately balancing it so net effect common mode noise which is not going to be a problem.

 

The capacitors I suggested are comonly used as supressors in all sorts of mains appliances, hence why I picked it. You may find one kicking about or in a local electrical repair shop can give you one.

 

 

Enough from me for now.. I will take a look again later and check what I have written makes sense.

 

Jon.

[laimeduck]

Thanks to everyone for replying, especially Derek Brambles & Keith - you have given me much to work on! I will keep you informed - I haven't had chance to test things yet, but will be using the van in anger this coming weekend. Will advise what I find.