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Discussion Starter · #1 ·
Sunday is probably not the best day to try to elicit the help of the electrical professionals on this forum, but hey, it's wet and miserable out there...

I'd like to keep the existing courtesy lights, supplemented by two more courtesy lights and some other 'leisure' lights, but I'd like them to be powered by the leisure battery. There are a number of threads on this forum that seem to discuss how to achieve this, but I've been left unsure if any of the offered solutions will work for me.

So this is my understanding of the existing circuit and my proposal for a new circuit:



Here is the link to the RS components solid state relay: DC Switching Plug In Relay 1 - 48 Vdc 5A A bit more expensive than I expected, so if you know of any alternatives...

My plan is to use one of these relays for each front/centre/rear 'zone' (it's an 08 Combi, so the side door turns on front & centre and the rear door does the back). The 'Manual Switch' will simply earth all lights so they all come on together (and don't time out when parked up).

My questions are: 1) will this work? and 2) do I have to put a resistor in place to deal with CAN or will the resistance in the relay be sufficient?
 

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Seems reasonable at a quick glance.

One question - any specific reason why you've chosen a solid state relay (and a DIN rail mount one at that)? I would have thought a conventional mechanical relay would have done the job fine and been a fair bit cheaper (less than a fiver each) and more compact. IIRC the advantage of solid state is low noise, low power consumed when on, and ultra-fast switching - none of which seems important in this case!

Not sure about needing a resistor, but I have my doubts that any of the interior lamps are monitored by any BCM, so you probably don't need to worry about so-called "CANbus compatible".
 

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I am an electrical numpty but want to do similar... Why do you need to involve the vehicle battery at all? Why not have the interior lights just on the leisure battery?... Is just take existing circuit but power it from the leisure battery alone
 

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Hi,

See my thread...

http://www.vwt4forum.co.uk/showthread.php?t=320487

Both the 'live' and the 'switched earth' run through the bcm i believe. This would make sense as you wouldn't have one switch for the interior light and another for the cluster display, alarm etc. So when people talk of a switched earth it is more of a virtual switched earth, and the constant live isn't constant!!!

Regards,

AB.
 

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Discussion Starter · #5 ·
Hi Abingdonboy

Your post was partly my motivation! I wanted to completely isolate any dependence on what the bcm would choose to do but still have the convenience of the lights coming on when I open the doors. Cornwallconvoy: I often use the van as a quick changing room between bike ride and pub, but will also need lighting for camping etc. Hence the relay and the manual switch to earth.

Here's a slightly updated proposed circuit using a standard (but SPDT) relay as suggested by Triffic:

 
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