Autoelectrickery co...
 

Autoelectrickery confusion

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I am attempting to fit a USB port in my car to replace one that has broken. By broken I mean that when you pushed a male end in the receiver would push back into the dash.

I bought a nice dual usb-c and usb-a switch to fit my car from a reputable auto electric company. Removed the old switch and it is fed by red black white and green wires. Inputs for the new switch are red black and blue and go to a connector to fit into the back of each the usb ports.

Google says the white and green can be capped or joined to blue… they’re really thin so I join them and all the wires are joined with solder heatshrink connectors.

I’m just fitting one of the ports for now because the wires are easily available from the single port I’m replacing.

Fit it together and there’s nothing happening at the port. 5v at the connector into the back of the port (ie after my connections) but I’ve even dismantled the switches and nothing is happening on the other side… they’re connector is the same for both ports and neither work.

Is the whole thing buggered or am I doing something wrong?

 

 


 
Posted : 21/02/2026 10:56 am
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well.. the fact that it has 3 wires going to it is cconfusing.

Is the 3rd wire not be a data line? or illumnition?


 
Posted : 21/02/2026 11:02 am
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As I understand it the third wire (and fourth) are data 


 
Posted : 21/02/2026 11:17 am
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Four connections is reasonable for USB A: Ground, 5V (edit aka VBUS), Data- and Data+

I'm not an electronics person, but a bit more detail of the port and vehicle might help someone who is


 
Posted : 21/02/2026 11:26 am
rogerturner reacted
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Have you blown a fuse while connecting it all up? 


 
Posted : 21/02/2026 11:27 am
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Did the reputable auto electric company not provide instructions?

With the caveat that all the wire colour reliably tells you is the colour of the insulation, I would assume the four wires to a USB port are VCC, Gnd, Tx and Rx (power, ground, transmit, receive).  Quite why something is telling you to short out Tx and Rx I can't fathom, nor do I know why your "switch" (whatever that is) is only expecting one data wire.  Assuming that it even is a data connector at all and not a switched live or something.

If I were to guess I'd say that your replacement is power only rather than power and data, and the "doing something wrong" I'd be doing would be guessing.

 


 
Posted : 21/02/2026 11:29 am
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Google suggests that:

Red is the VBUS, White is Data-, Green is Data+, Black is Ground

Red and black will give you power, which tends to suggest that connecting the two data wires together has mucked something up


 
Posted : 21/02/2026 11:36 am
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I tried without the green and white wires and it made no difference.


 
Posted : 21/02/2026 12:13 pm
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Posted by: oceanskipper

Have you blown a fuse while connecting it all up? 

no - there’s still 5v to the wires

 


 
Posted : 21/02/2026 12:16 pm
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post a link to the usb in question 


 
Posted : 21/02/2026 12:32 pm
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Posted by: reeksy

no - there’s still 5v to the wires

 

You are testing it with the ignition on, aren't you?


 
Posted : 21/02/2026 12:48 pm
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https://www.stedi.com.au/new-d-max-colorado-2012-push-button-switch.html


 
Posted : 21/02/2026 12:48 pm
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Posted by: Cougar

Posted by: reeksy

no - there’s still 5v to the wires

 

You are testing it with the ignition on, aren't you?

of course 

 


 
Posted : 21/02/2026 12:49 pm
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So if there's no power to the wires then that's not a switch problem.


 
Posted : 21/02/2026 12:52 pm
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Is it possible that, yes there’s 5v there (as you stated) at the wires but it won’t take any load due to not getting a switched voltage to the blue, so like a car radio it gets  a feed to enable power to the USB whilst the courtesy light is on or whatever?

It does sound like the wrong socket and won’t give you a data connection.

 


 
Posted : 21/02/2026 1:41 pm
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Red = positive
Black = negative
Blue = ignition positive?

Just a thought, but a number of vehicle electrical devices* have two positives, one for 12v and the other for the ignition positive which actually switches it on.

* have a marine stereo in front of me right now with this exact wiring.

5v at the connector into the back of the port (ie after my connections) but I’ve even dismantled the switches and nothing is happening on the other side…

Are you sure the new usb port isn't expecting 12v?


 
Posted : 21/02/2026 1:51 pm
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Also is it a switch or a socket? The link shows a wiring diagram for a switch, if I read it correctly.

Another thought, aftermarket USB ports often have 12-5v step down so you can wire them straight in. I’ve just fitted one to my car. If your socket is expecting 12v, obvs it won’t work on 5v

 

edit: too slow


 
Posted : 21/02/2026 2:06 pm
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Posted by: sharkbait

Are you sure the new usb port isn't expecting 12v?

If you've got 5v at the wire now then you need a new 12v supply to the new port - but you still won't have data.

(My money is on blue wire being for a dash light connection)


 
Posted : 21/02/2026 2:12 pm
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sharkbait and jamesoz seem to be on the money

It's a charger (if I've got the right doodah), not a data connection. I can't see a data connection on their support pages (scroll down to related articles)

https://support.stedi.com.au/hc/en-us/articles/43905889684505-Carling-Type-Rocker-USB-C-USB-A-Volt-Meter-Switch-Wiring-Diagram


 
Posted : 21/02/2026 2:15 pm
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You’d normally expect a 12v feed to a cigar socket, and I expect most aftermarket USB sockets would also take 12v as the input and then output 5-20v depending on the device being charged.

Can you post a picture of the wires?  As it was never a 12v socket and always a USB, there is a reasonable chance that it’s fed from your infotainment screen and is essentially a USB extension cable that takes 5v and the data from the screen.


 
Posted : 21/02/2026 5:16 pm
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Whenever I’ve fitted an aftermarket usb socket to a 12v vehicle electrical system I used a 12v to 5 v step down converter then took this feed to the usb socket.

 

 


 
Posted : 21/02/2026 5:38 pm
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Whenever I’ve fitted an aftermarket usb socket to a 12v vehicle electrical system I used a 12v to 5 v step down converter then took this feed to the usb socket

Seems like extra effort. The diagram Timba found shows 12v in.


 
Posted : 21/02/2026 6:46 pm
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**** me dead! Of course the power was coming from the back of the entertainment system wotsit at 5v already…

Thanks for the common sense everyone.

So today involved buying some micro fuse taps. Then buying some more with the correct type of fuse taps. Then finding the fuses in the fuse box are another type that are kind of compatible.

Got it working, however when I finally went to fit the socket into the dashboard it’s too ****ing small to click home. Arse.


 
Posted : 22/02/2026 8:39 am
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Cut a square  of thin plastic the correct size so the new usb socket fits in and the tabs locate them leaving a 5mm surround use some thin strips of double sided tape to stick it to the dashboard, or super glue if your feeling brave 


 
Posted : 22/02/2026 8:49 am
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That’s a nifty idea. 
I think I’m more pissed off that it is supposed to fit my car. I even popped out a blank in another spot to see if it would fit and that was wrong too.

 


 
Posted : 22/02/2026 8:56 am
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Posted by: reeksy

That’s a nifty idea. 
I think I’m more pissed off that it is supposed to fit my car. I even popped out a blank in another spot to see if it would fit and that was wrong too.

Can you cut a hole in the blank? That'll be neat and the correct colour

 


 
Posted : 22/02/2026 10:13 am
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No I don’t think so.

There’s a row of ports and a fag lighter down low in front of the gear stick so you can’t see much. It’s flopping around loose at the moment but if I put the extra bit of plastic behind the dash it will be invisible anyway.


 
Posted : 22/02/2026 10:24 am