Flickering lights

[ProfJohnL]

My van has the same feature. I believe it’s a back emf from the pump motor as it stops rotating. Not remotely concerned, but if I was I’d introduce a diode in series with the pump on the negative side.

Why on the negative side? that will have the effect of raising the potential of the pump negative by a diode drop, and will do nothing to stop the back emf from the motor affecting the +ve supply.

It would make more sense to put a diode in the +ve supply to the pump.

But what would make even more sense would be for the control circuits to be properly designed to stop the issue in the first place.

 

[Icaru5]

My van has the same feature. I believe it’s a back emf from the pump motor as it stops rotating. Not remotely concerned, but if I was I’d introduce a diode in series with the pump on the negative side.

Why on the negative side? that will have the effect of raising the potential of the pump negative by a diode drop, and will do nothing to stop the back emf from the motor affecting the +ve supply.

It would make more sense to put a diode in the +ve supply to the pump.

But what would make even more sense would be for the control circuits to be properly designed to stop the issue in the first place.

It wouldn’t have any adverse effect. Nor would its intention be to stop the back emf from affecting the +’ve supply.

I believe that the flickering of the overhead LED lighting is being caused by the pump momentarily generating a small emf on the -‘ve rail. After studying the simple wiring diagram, this is the only possibility as the +’ve supplies to all of the affected luminaries are broken by the air gaps in their respective single-pole switches.

The purpose of the diode would be to prevent this small voltage from leaking onto the -‘ve rail.

With regards to the circuit design, no doubt the fundamental design originates from when the manufacturer was fitting tungsten filament lamps rather than the latest generation of LED luminaries, which obviously exhibit this characteristic when there is a small, floating emf present on the -ve side.

Now of course by definition, applying a small voltage to the cathode of a conventional LED would have no effect whatsoever, but the latest generation of luminaries which are commonly referred to as “LED” contain their own circuitry to illuminate a number of individual diodes, and bear very little resemblance to the red LED’s which rose to prominence amongst electronic enthusiasts and hobbyists during the 1970’s !

 

[Craigyoung]

Is there anything new to report on this issue? My Quattro FB has the same 'feature' and I know if I take it to the dealer they will insist they don't know / can't find / haven't heard of this problem.

Sorry leewurf , been away a few weeks & just back , we had our van in to get sorted a few weeks ago before I went away and removed the bunk spotlights and replaced them with new ones and full new wiring system from the spotlights but my flickering was from my wife igniting the gas , all is well now and as for the pump, they did put some kind of rubber grommet over the edge of it to silence it .

Craig

 

[GD485]

By “flickering lights” do you mean they flash when they are switched off or when they are on?
Occasionally my under cupboard light (LED) flashes even though it is switched off when the pump fires up or the master switch is switched off.
I put this down to a fast spike being generated when the pump or caravan switches off.
I dragged out my old oscilloscope and connected to the lamp. My suspicion was confirmed. I got a peak voltage of 96v but less than 25mS. As an experiment a 0.1uf capacitor was connected to the light feed and ground.
This suppressed the spike and stopped the light flashing.
I think the same trick may need th be repeated with each light.
I didn’t bother as the flash really doesn’t bother me too much.
I didn’t investigate the flickering when the lights are switched on but I think this maybe no more than poor voltage regulation or wiring resistance.

Good luck with yours!