Topic: Dash cam hardwire, help with fuse tap!

[milkpumba]

Just bought an A119S and plan to hardwire it. Will be hardwiring it by using an Add-a-fuse. Might be a stupid question but I know that I need to pull out a fuse (let's say the cigarette fuse) and then add it onto the bottom portion of the add-a-fuse. What about the second fuse for the top port of the add-a-fuse, how do I find out which one to use? I'm so lost...

Here's the hardwiring kit that I got for the dash cam: https://www.amazon.ca/Spy-Tec-Dash-Camera-Vehicle/dp/B01N0GR4ON/ref=sr_1_4?ie=UTF8&qid=1490693844&sr=8-4&keywords=a119+hardwire

Here's the dash cam: https://www.amazon.ca/gp/product/B01NAERFRT/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

[kijho]

Use the same fuse as the fuse you're tapping into, Ie. You'll want 2x 10amp fuses plugged into your tap. I believe one acts for the original function and the second acts for what you're adding (dashcam).

My video may help you Start around 2:30 to see the exact fuse / tap setup.

[Unholysavage]

add a fuses are pretty simple, it usually takes 5x longer to finda suitable circuit to use than it does to plug one in.
the first thing you need to decide is whether you want to use a switched circuit (only has power with the key turned), or one that's always got power. some people want their dash cams on 24/7, others only want it recording/drawing power when they're driving. a test light or multimeter are the easiest tools to use, but trial and error works too. the last two add a fuses I've used used the windshield wiper circuits for switched power.

pull out an existing fuse that suits your purpose (make sure it's the same size as your add-a-fuse holder or it won't plug in), and plug your add a fuse holder into that empty slot. take the fuse that you just pulled out and plug it back into one of the two slots on the top (should go into the slot that isn't being used for the new power lead, it should be obvious to see when looking at it from what I remember). this re-fuses the original circuit that you're Y-ing off of.
then plug in a second fuse next to it, which fuses the new power lead for your cam.

I can't imagine you need anything more than a 3-5A fuse to power a dashcam. if your dashcam has a fuse size suggestion, use it.

[RockThePylon]

It's powered by USB, I'd keep the fuse size max. 3A.

[milkpumba]

Use the same fuse as the fuse you're tapping into, Ie. You'll want 2x 10amp fuses plugged into your tap. I believe one acts for the original function and the second acts for what you're adding (dashcam).

My video may help you Start around 2:30 to see the exact fuse / tap setup.

Watched your video and you used 2x 7.5amp fuses on your tap or am I missing something here?

It's powered by USB, I'd keep the fuse size max. 3A.

Just out of curiousity, what would happen if I used a fuse more than 3 amps?

[RockThePylon]

Just out of curiousity, what would happen if I used a fuse more than 3 amps?

The fuse is supposed to blow before the wiring/component is damaged. If the fuse is rated for more than your wiring, there's no point.

Skinny wires don't carry a ton of current before they start getting start-a-fire hot. USB is often 28AWG, which isn't good for much more than 1amp before they start getting warm, 10amps would make em glow red real quick.

[kijho]

Should I change my fuse down to something lower like 3a? 

How do you know which fuse is for which line on the tap, though? Like I should keep the 7.5 for the ignition then change which one to 3a?

[milkpumba]

The fuse is supposed to blow before the wiring/component is damaged. If the fuse is rated for more than your wiring, there's no point.

Skinny wires don't carry a ton of current before they start getting start-a-fire hot. USB is often 28AWG, which isn't good for much more than 1amp before they start getting warm, 10amps would make em glow red real quick.

Okay so I think I got it! If a fuse rated for more than the wiring is used, then basically if things do go wrong, the wiring will get uckfayed before the fuse can do it's job of protecting the circuit?

Should I change my fuse down to something lower like 3a? 

How do you know which fuse is for which line on the tap, though? Like I should keep the 7.5 for the ignition then change which one to 3a?

I was reading threads online last night and people said that you're supposed to put the fuse that you took out of the fuse box on the bottom part of the tap, and the new fuse on top.

[RockThePylon]

Should I change my fuse down to something lower like 3a? 

How do you know which fuse is for which line on the tap, though? Like I should keep the 7.5 for the ignition then change which one to 3a?

Probably should. If the camera claims to draw 1A, a 2A fuse should be plenty. They don't blow the instant you go over 2A, so higher startup draw should be irrelevant.

Makes sense that the top fuse would be for the add-on circuit, though.

Okay so I think I got it! If a fuse rated for more than the wiring is used, then basically if things do go wrong, the wiring will get uckfayed before the fuse can do it's job of protecting the circuit?

Yup. The fuse is the weakest link.

[Unholysavage]

based on memory, the fuse for the add a circuit should be directly in line with the wire coming out of it.
what size wire is with your add a circuit? every add a circuit I've owned has had a 16ga wire lead coming out of it. assuming yours is 16ga, too, with a ~7ft wire run most online 12V charts for current draw show that you should be fine with up to an 10A peak draw.
not all 16ga wire is made equally (same can be said for fuses), so I'd err on the conservative side and stick with a <5A fuse as others have mentioned.