Decent 12V keyed "accessory" power source

[Greg Roles]

Hi all,

This may have been answered elsewhere, I had a bit of a look online, and couldn't find anyone who had a really good accessory power source in their T5, as it turns out the cig lighter and more surprisingly the stereo "accessory" lead has power all the time. Gotta love CAN BUS cars....

I wanted keyed 12V power, and also wanted the new radio to have a true accessory power source rather than the "acc" lead getting constant 12V power via the factory loom. It's only a China radio so not very well documented.

Read about a specific fuse with a tiny wire on Brickyard, and then that some people were using the back of the light switch, but these were either way too small and or only live with the engine actually running.

I did a fair bit of unsuccessful prodding and poking with my multimeter, and short of going to the ignition barrel itself, finally found what appears to be true accessory power in a hefty source.

When you key on and turn off, there is a decent relay noise from below the steering wheel. It also remains on for about 30 seconds after power off. On investigation there is a smaller 40A relay, and a hefty "100" one, and it is from this latter relay I took a source of keyed accessory power. I used this to trip another relay on the cig lighter power, which is always on, and decent sized wire. This "100" relay has a decent build and thus power handling, so the tiny bit I am pinching to run my additional relay is unlikely to cause any problems, but I will monitor it and see how it goes.

Here's a pic of both the fuse, location, and how I soldered onto the correct leg ( number 5 ) to get my accessory power. The relay sits a little proud now obviously but has plenty of connection still and working as per normal. I'm done wiring up all the accessories in my dah now, and have powered USBs and my gauges all set up, just need to stick them all up out of the way so the head unit can slide in, quite a feat in itself!

[Sunny43.5]

I have a Chinese Head unit in both our vans and they plugged straight into the original head unit plug . On our newer model the unit supplied can bus converter was used but our older one does not need the converter to be connected . Have been using both of them for well over 12 years or more with no issues .

[Greg Roles]

I have a Chinese Head unit in both our vans and they plugged straight into the original head unit plug . On our newer model the unit supplied can bus converter was used but our older one does not need the converter to be connected . Have been using both of them for well over 12 years or more with no issues .

Yeah probably the case and good to know, I was all about avoiding any possible voltage drain as this will sit for weeks at a time, and a Chinese head unit is the most likely culprit in my mind. Anyway it all works well, plus I needed this switchable source for aftermarket USB chargers, Speedhut gauges and a bit more trickery I've put into the dash / cabin!

[Sunny43.5]

Rather than soldering onto relays why not use "Add a Fuse " much safer https://ceautoelectricsupply.com/wp-...Tap_In_Use.jpg

[The_Hawk]

or at least a wire tap?

SCA Electrical Terminals - Wire Tap Connector, 3-4mm, 6 Pack | Supercheap Auto

[Sunny43.5]

or at least a wire tap?

SCA Electrical Terminals - Wire Tap Connector, 3-4mm, 6 Pack | Supercheap Auto

We used to use those back before add a fuse came along , they arent as reliable as they cut the strands of wire and over time wont conduct electric power as they get loose around the cable . I used to import the add a fuses from China in the hundreds still have some if someone needs a small number .

[The_Hawk]

Agreed they are a potential point of failure, but they have to be better than soldering to the relay.
I tend to use the wire taps when I'm being lazy and just want to tap something remotely (like my reversing camera) but will use a tap when I'm installing a dedicated thing like a reversing camera where the add a fuse are magic