Switched Power pickup

[Blumr2]

Hey All, 

I'm looking at installing a DC DC Converter for USB power supply, i have a Dual one in the 5 series family hack and works great, however in the 986 i connected to switched power from the fuse box a well as from the audio / telephone supple and Nav system ( as my Nav CD unit is long dead ) but no GO !  connect the converter to a permanent 12V supply and no issue working at all.

I can't work it out, the switched ha 11.68v on acc but with the engine running has 12.68v - 13.70v so there shouldn't be a problem but the device still won't kick.

I have put a ground to a body bolt, maybe you need  to run it to the harness but that should be to the body anyway ! the unit would work between 7-21v input so low power with out the engine running shouldn't be an issue.

Has anyone used the connections and switched etc for aftermarket dash cam, GPS etc and had any similar issues? 

 

cheers all.

[neil.c]

Have you checked the voltage with the device connected to see if it is pulling the voltage down?

Earth on the body should be fine.

[Blumr2]

Boy hood mistake NO ! i did without it connected to make sure the voltage increased as switched from acc to IGN and that was correct.

the device works if on a perm 12V supply and also hooked up a relay off the switch to act as a switch and perm 12V and the relay didn't kick as well.

it may need a closed loop for the switched power and not to body earth and it does come one and go off slowly so without a jolt it may not wake the device ?

Odd one, was going to try and hook it up to the BMW where if fitted one the same and see if the same happens or not but from memory the BM switched power is more definitely on or off.