Roof Cables for 12V?

Hi, new here, in the early stages of a van conversion of a 2017 promaster. I’d like to prewire my roof so I can later add some lights. Any recommendations for cables that can withstand the tough conditions (sunlight, ice, snow) up on a roof? I’m thinking 12/2 or 14/2 stranded, but am not sure about what can withstand conditions on a roof. Thanks for your help! Maybe someone has purchased light systems for roof and knows that they come with cables, and that you should use them instead of prewiring with others before you get the system because otherwise you’ll need to connect wires on the roof and that’s not ideal. Any thoughts? Thanks!

Greetings & Welcome!

Your wiring size needs to be determined by the load they will carry.


"Be the reason someone smiles today!" ~ Van_Dweller

Yes, thanks. I know I’ll need 14 awg. But I’m not sure whether, for example, marine grade romex jacketed will work, or if there’s a more weatherproof option out there. The top of a roof is a brutal environment - extremes in heat, moisture, cold, vibration, wind…


Normally with the possible exception of solar, no wires are run on the roof. For lights etc. the wires come up through the roof and directly into them without being exposed to the weather. With solar, the wires are shaded from the sun at least.

I think I would try to wrap whatever wires I was using, to help protect them. I don’t know what wire insulation is best, but added protection certainly can’t hurt.


"Be the reason someone smiles today!" ~ Van_Dweller

What I’ve seen people do in some off road builds for their lights, they use a hose (well, something that is meant for cables) that goes along the a-pillar from underneath the bonnet to the roof. That way you do not need to make any holes in the roof itself.

This is just wires going outside

You could draw several wires through a hose so it would look nicer and shield them from the elements at the same time.

I don’t know how you would shield the cables on the roof though if you pre-wire them. Could you just roll the cables under the bonnet and finish them when you get the lights?

Marine wire, which is tinned, and hardware. Blue Seas Systems has all sorts of HD hardware. CRC HD Corrosion Inhibitor spray on all exposed hardware. Split loom all wiring for a clean,pro look. Ancor heat shrink connectors.