2 replies to this topic

[JonnyAlpha]

Hi;

 

I am fitting a new radio (well second hand). On the existing radio when you press the horn the radio sound mutes so there may be a wiring issue here? so I may re-wire it.

 

Couple of questions:

 

1. What gauge wire should I use?

 

2. Where should I pick up a constant 12v and switched 12v?

 

3. Where should I ground the radio power?

 

Many thanks  

 

 

[wile e coyote]

Can't comment on guage - I have a huge roll of 27A rated cable that I used - probably overkill but there you go....

 

I am loath to splice anything into existing wiring so run new - constant 12V (with a 15a fuse inline)  taken from the solenoid, switched from 2nd or 3rd  fuse down of a 4 fuse block, cant remember which offhand but easily checked!  both entering via a new 10mm hole in the bulkhead (with obligatory grommet) - you may get away with smaller but my vac guage pipe uses the same route,  and earth to a self tapping screw into the bulkhead or heater screw head....

[JonnyAlpha]

Can't comment on guage - I have a huge roll of 27A rated cable that I used - probably overkill but there you go....

 

I am loath to splice anything into existing wiring so run new - constant 12V (with a 15a fuse inline)  taken from the solenoid, switched from 2nd or 3rd  fuse down of a 4 fuse block, cant remember which offhand but easily checked!  both entering via a new 10mm hole in the bulkhead (with obligatory grommet) - you may get away with smaller but my vac guage pipe uses the same route,  and earth to a self tapping screw into the bulkhead or heater screw head....

 

Thanks for the help.

 

In my setup I failed to mention that as well as the radio I will be powering a Raspberry Pi Car PC / Touchscreen (Low Powered Mini PC). The Pi powers the touchscreen which in turns gets its power from a 3A Car Switch circuit board designed to initiate a shut down when the ignition is turned off (i.e. when it senses that there is no longer a switched 12v).

 

Main Power Wire

I need to calculate the gauge of wire to run from the Solenoid to a distribution box (this wire will feed both the Car Radio Head Unit and the 3A Switch for the In Car PC). I intend to instal an inline fuse on the main power wire within about 12 inches of the solenoid. The wire size will depend upon the amp rating of the Head Unit and the Car PC Switch. The radio is fitted with a 10Amp Fuse so assuming the PC Switch is 3A then the combined draw is 13Amps. Based on this 18AWG or greater (e.g 16AWG) would be suitable.

 

Switched Power Wire

If I run the 12v switched from the Cars Fuse box then this will already be protected so wont need an additional fuse? Again the switch wire needs to be 18AWG or 16AWG.

 

Ground Wire

Depending on whether I use separate ground for each component or a combined ground the gauge of the ground wire needs to match the supply so 18AWG or 16AWG if I use a combined ground on the supply side of the distribution point. The ground will be as close to the distribution point as possible so into the bulkhead or under the dash rails? 

 

Fuses

For the fuse on the main power wire if the Radio has a 10Amp Fuse Fitted to it and the Car Switch is 3A then an 13Amp Fuse or lower should be OK? If I then also fit a 10Amp In Line fuse between the distribution box and the Head Unit and a 3A Fuse between the Distribution Box and the 3A Switch everything should be adequately protected?

Edited by JonnyAlpha, 30 December 2016 - 11:45 AM.