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What are your thoughts on whether I can power a CB radio from the internal light. I have deducted that the centre wire (red/black) is the live withe the other 2 wires being permanent earth and convenience earth. Is the power enough and is the wire thick enough. Some people have said yes it’s ok but some people have said no it’s not advisable to.

Would appreciate any more thoughts on this one, currently powering off a fuse with unit in lower dash. Ideally I want to place the unit in the cubby hole in roof and it made sense to use the light wiring there rather than feed a new wire up through.
 

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The correct way to power any transceiver is directly off the battery - positive & negative fused cables sized to suit the load when the unit is transmitting.
 

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What are your thoughts on whether I can power a CB radio from the internal light. I have deducted that the centre wire (red/black) is the live withe the other 2 wires being permanent earth and convenience earth. Is the power enough and is the wire thick enough. Some people have said yes it’s ok but some people have said no it’s not advisable to.

Would appreciate any more thoughts on this one, currently powering off a fuse with unit in lower dash. Ideally I want to place the unit in the cubby hole in roof and it made sense to use the light wiring there rather than feed a new wire up through.
I would have said it may be a bit too much.
It is actually a very easy thing to route a wire up behind the A Pillar trim and across to the cubby (the T5 is one of the easiest vehicles to do that to in fact) so I would do that.
FWIW, I wired mine from a direct battery supply, but via a relay that gets energised by the ignition signal, so a good solid supply but only live when key is in.
 

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Hello Karen,

What you want to do is the same as I have done, the interior light fuse is 15 amps, the CB draws about 2 amps max on transmit,
maybe even a bit less, so the wiring will handle it ok, I've been using mine like that for 6 years without any trouble, except for forgetting to switch it off sometimes, because it draws a small amount of current in standby it will discharge the battery somewhat if left on for a day or two.
The CB should have its own inline fuse (usually 3-5 amps). I'm assuming you are fitting a standard UHF CB transceiver radio.
 

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My interior light fuse in my T5 is 7.5A
Rus
Yes, that's correct, there is a 15A fuse to the control unit and 2 x 7.5A fuses after the control unit. so the radio if
connected to the interior light would be through one of the 7.5A fuses, however, with most later series UHF CBs
drawing less than 1 amp on standby, and less than 2 amps on transmit then I consider it is safe to connect to the 7.5A
fuse (in reference to wiring and fuse sizes). Just rechecked recommended fuse size for my CB is 2 Amps.
 

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Just because you could, it does not follow under good electrical practices that you should.

Taking power for such a load off the lighting circuit is a shabby idea, the fuses are there to protect the cabling from excessive current draw, and adding such a load to a lighting circuit just shouldnt be done tbh.

The guys have tried to advise you but I suspect theyre facing the "but I really want to" principle, so go for it and maybe see why they tried to help. LOL:
 

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Perhaps this thread is not serving any useful purpose, as I'm not convinced that Karen.fisher999 has any intention of returning to it.

But... one of the frustrating things about the interior light circuitry is that as far as I'm aware, NONE of it is suitable to power anything other than the interior light, because there is no source of permanent live at the interior light fitting. On both the T5 and T5.1, the supply is on a PWM circuit that will dim it to (almost) zero after a period of inactivity. This makes the discussion pretty much irrelevant - you are going to have to run in a separate live anyway.
 

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triffic
I respect your knowledge of T5s, however, either you didn't read or take any notice or don't believe my comment in reply #5, "I've been using mine like that for 6 years without any trouble"

The positive connection of the interior lights is constant live, the negative (doors) connection is modulated for the dimming to off process by the control unit. Easy to make yourself aware, if you test it for yourself. The discussion remains relevant to the OP's enquiry, (although Karen.fisher999 is probably either rolling eyes or having a chuckle at this point of the thread).

mindriot
I respect you also are knowledgeable, but can't agree that adding a load of <175mA (receive) or an -intermittent- load of 1.5 - 1.7 Amps (transmit) is an excessive current draw, or a "shabby idea".

The OP wanted to know if "...it made sense to use the light wiring there rather than feed a new wire up through..." Since I've used the same without any problems at all (and made the calculations beforehand) then yes it's ok.
 

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Karen.fisher999
Just if you are still interested -
You should have enough replies with info to reach a decision, but I'll just add that if you are still concerned about any excess current draw you could change to LED lamps for your interior lights, requiring much less current than the originals.
 

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triffic
I respect your knowledge of T5s, however, either you didn't read or take any notice or don't believe my comment in reply #5, "I've been using mine like that for 6 years without any trouble"

The positive connection of the interior lights is constant live, the negative (doors) connection is modulated for the dimming to off process by the control unit. Easy to make yourself aware, if you test it for yourself. The discussion remains relevant to the OP's enquiry, (although Karen.fisher999 is probably either rolling eyes or having a chuckle at this point of the thread).
Ok, fair enough. Perhaps there are differences between T5 and T5.1. I have personal experience and have tested this myself (on a T5.1) to try to run a clock in the roof lining cubby hole. On my van, there is no permanent 12V supply there. There is a 12V supply that remains live as long as the ignition is switched on or you keep opening and closing doors, but once that stops, 12 minutes later the supply is dropped. I should stress that this is true on my van (2013 Kombi SE). It may not be true on others.

In order to run the clock, I had to run a wire up from the dash, which wasn't difficult as I also had to run a 5V supply to my dashcam, which for neatness is supplied from the headlining. It's almost trivial to do on a T5 - the most difficult bit in my experience being the removal of the A pillar trim.
 
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