Just got back from a 2 week stay in France, and despite having previously already replied to this thread stating that my Siena 6 TD (Dealer special of Sprite Major 6 TD) doesnβt do this, I can confirm that it does
Not a every time a tap is closed, but I would say around 50% of the time.
However, Iβm not remotely concerned and although I havenβt had the chance to investigate, I expect it to be as Howzatt says. Thereβs a slight change in tone of the pump just before it stops, as it is subject to an increased load, after which the pump abruptly stops and there is a very brief flash of the LED lighting strips above the kitchen units and those above the units in the rear.
Iβm not familiar with the design of this particular pump, but am now considering the possibility that after closing a tap, once the pump has re-pressurised the system, the 12v feed Is removed, and then the pressure within the system is causing the pumps impeller to momentarily spin the opposite way ? - as since the +12V feed to these LEDβs is physically switched, it is impossible they they are receiving power through the 12V supply, and so my suspicion is that when this occurs, the pump is somehow introducing a small back emf on the -βve (or 0V) rail which is enough to cause a momentary illumination of the LEDβs.
I will put my fluke meter across the terminals of one of the LEDβs when I can find their time and will report back. Iβm guessing that this has only become an issue with the later models of van with the LED lights.
I really hadnβt noticed this previously as during daylight itβs not easy to spot. It only came to my attention after my son used the bathroom tap during the night. Coincidentally, I hadnβt previously noticed the change in tone of the pump which occurs a couple of seconds after switching the tap off.
I really am not concerned about this, and if it is as above, If it does ever end up bothering me, I will just put a diode in the 0V (or -βve) connection to the pump.