Thanks very much for this information regarding the 'Resister Value' required from Pin#5 (or Pin 'X') to Ground:-
RE: Garmin Nuvi GPS Power Connector connector pinout
It was difficult finding USB Mini 'B' Plugs ,preferably 90 Degree angled UP, with a Pin 5 (or Pin 'X') that a Resistor can be soldered onto.
Garmin seem to mount the USB Min B Socket upside down (compared to 'conventional' orientation) on Nuvi GPS Navigators for some reason?
I did come across some 'Tip' adapters that came with 'SBC-10' from CDR King, among which was DC 2.5mm sticking out of the shell of a USB Mini B. The shell had a detachable top, and there was a 200K Ohm Resister to GND. Rather than remove it, I soldered a 20K OHm resister in parallel with that 200K Ohm already fitted. The combined Resistance Value is 18.18K and worked fine in my Garmin Nuvi255
Except I use my Garmin Nuvi 255 on my Motorcycle in a handlebar mounted water resistant case. There is not enough depth in the case, to connect the DC 2.5mm Female connector onto the back of this Adapter 'Tip'.
The solution was to cut the shell with a mitred 45Degree and 'Superglue it back together, so it became 90 degrees. Did the same with the clip on shell cover. I wrapped insulating tape around to help keep moisture out and more mechanical strength (fill the inside with epoxy glue, would be better now I know that it works).
Have not been able to find such Adapter Tip on its own (except from China if you order 50 or more, and just a hole (presumably for a cable or DC2.5mm Plug, but cable strain relief not DC 2.5mm Plug supplied with it). Finding DC 2.5mm Socket is bit more of a problem.
I also experimented, by cutting the cable of the genuine Garmin 12V Power Cable.
There is 3 wires coming from the 12V Cigar Lighter plug body - Red (+5V), Black (Gnd) and White (VO+) which is presumably via a 'Pull up' Resistor off the +5V rail.
This seems logical, to give a potential divider with the Resistor Value to Gnd on Pin #5 of the Garmin Nuvi USB ID Volts = 1.78V. In theory if the Resistor on Pin#5 was about 18K Ohm, then 33K Ohm as the Pull Up Resistor connected to that White Wire, should give the desired USB ID Volts.
However since the Garmin will give a USB ID Volts reading, when a USB Mini B with such Resistor fitted is connected but no 5V yet applied, there must be another Pull-up Resister, within the Garmin Nuvi itself, surely?
Anyone able to confirm this and state what is the value of such pull-up Resister in a Garmin Nuvi?
If that white wire (VO+) of the Garmin 12V PSU Cable, does not connect to Pin #5 of the Garmin GPS, the +5V Power does not turn on.
I decided to join the cut cable of my Garmin 12V PSU, with a 'USB A Female' Socket, on the 12V Plug end, and a 'USB A Male' Plug on the USB Mini B end. This means I can use that cut cable from the Garmin 12V PSU in any USB socket and it connects as a Power Cable (which is what I want on my Motorcycle 12V outlet with PowerJolt Duo USB (from Griffin Technology). This allows me to power my Garmin Nuvi off the 12V Motorcycle Battery via the Griffin PowerJolt or equivalent (and still have another USB for charging my Cell phone, or something).
Trouble is the Garmin 12V Power Cable, now wired to 'USB A Female' Socket, instead of the special 'USB Mini B' Plug, with that 17.3K Ohm Resister to Gnd, does not power up! (until I plug in the Nuvi with that other half of the cable, now terminating in 'USB A Male' Plug.
So I am contemplating if a Resistor (200K Ohm) can be fitted inside the Garmin 12V Cigar Lighter Plug body from that White Wire to Ground (I already know 200K with 18K in parallel works, with correct USB ID Volts saying it is Power Cable). If this allows it to power up and give +5V output, with no Nuvi (or the special cable to USB Mini B plug) connected, then it can be used to power other USB devices (or my Garmin Nuvi if the PowerJolt fails).
Will give an update, if fitting such Resistor works (or if different Value required)