Wiring a Fuse tap

[Mpa1991]

Hi,
Absolute novice here, sorry if this question seems dumb but I'm confused. Almost done installing heated seats (i know this site is about dash cams but i saw posts about the add a fuse here so thought maybe you could still help) in my wife's car, just need to plug in to the fuse box. Every tutorial either glosses over the wiring or only discusses the hot wire going into the add a fuse. There are two wires coming from my device and I'm unsure how to wire this up. I already know which spots in the fuse box are only on when the car is on, which side of the fuse is the hot side, but no idea how the wiring works. Thanks in advance to anyone who can help my inept self.

 

[Mtrev]

The second pic is a fuse holder, designed to be tapped into a wire. The add a fuse will remove the need for that, just put it’s fuse into the top slot of the add a fuse (assuming it’s the correct size, otherwise you will need a new fuse).
The add a fuse then sits in the fuse holder with the original fuse in the bottom slot. The red wire connects to the power wire of whatever you are fitting. For a heated seat a 10A fuse sounds quite low though, is that correct? Also check the circuit you are using the add a fuse on can carry the extra load, in this instance I would put the leg on the wire side of the add a fuse into the hot side of the fuse box, this would mean the seat supply has to go through both fuses meaning that the circuit can’t be overloaded.
Dash cams are low current so it’s not that important but with heated seats it will be more critical.

 

[Mpa1991]

The second pic is a fuse holder, designed to be tapped into a wire. The add a fuse will remove the need for that, just put it’s fuse into the top slot of the add a fuse (assuming it’s the correct size, otherwise you will need a new fuse).
The add a fuse then sits in the fuse holder with the original fuse in the bottom slot. The red wire connects to the power wire of whatever you are fitting. For a heated seat a 10A fuse sounds quite low though, is that correct? Also check the circuit you are using the add a fuse on can carry the extra load, in this instance I would put the leg on the wire side of the add a fuse into the hot side of the fuse box, this would mean the seat supply has to go through both fuses meaning that the circuit can’t be overloaded.
Dash cams are low current so it’s not that important but with heated seats it will be more critical.

Thank you for your answer, good to know that i dont need both parts. The Fuse holder it came with had a 10a fuse already installed in it. Removing the fuse holder will still leave me with two wires. While one gets crimped into the fuse tap, where does the other wire go?

 

[Mtrev]

Thank you for your answer, good to know that i dont need both parts. The Fuse holder it came with had a 10a fuse already installed in it. Removing the fuse holder will still leave me with two wires. While one gets crimped into the fuse tap, where does the other wire go?

If you only have 2 wires to power it then the other one will be a ground wire which goes a bolt or ground connector which has an electrical path back to the cars body and hence the negative of the battery.

 

[Mpa1991]

If you only have 2 wires to power it then the other one will be a ground wire which goes a bolt or ground connector which has an electrical path back to the cars body and hence the negative of the battery.

Got it. Thank you so much. I feel like a moron not knowing that but gotta learn somewhere. You are an awesome person. Thank you again.

 

[LAKKS]

One point about using fuse taps: the side opposite of the outgoing wire is where the source of the power is coming from (right side in the photo) and the wire side is outgoing. When testing the fuse box for power, one of the plugs where the fuse goes into will be hot. That is the supply side. If you put the fuse tap into the fuse box with the wire facing the hot side, the fuse won't provide protection. I learned this from another contributor here in this forum, even though I'd been using fuse taps for years!!! Some fuse boxes won't have space for you to plug in the fuse tap facing the correct way. I had to find another fuse that allowed clearance.

 

[Mtrev]

One point about using fuse taps: the side opposite of the outgoing wire is where the source of the power is coming from (right side in the photo) and the wire side is outgoing. When testing the fuse box for power, one of the plugs where the fuse goes into will be hot. That is the supply side. If you put the fuse tap into the fuse box with the wire facing the hot side, the fuse won't provide protection. I learned this from another contributor here in this forum, even though I'd been using fuse taps for years!!! Some fuse boxes won't have space for you to plug in the fuse tap facing the correct way. I had to find another fuse that allowed clearance.

The wire is always protected by at least one fuse by design of the fuse tap. If you put the wire side (b) into the hot side then the current passes through both fuses, put it the other way around and only the new fuse protects it.
In this case as they are using it for heated seats I advised they put the wire side in the hot side, this means that both circuits together can only pull the amount of the original fuse and therefore not overload the supplying circuit above it’s designed level.

 

[SawMaster]

It's an ongoing debate regards fuse tap orientation, but as a practical matter with dashcams using so little current it doesn't matter. A higher-current draw would matter more. I've never heard of one single case with dashcams where orientation caused any kind of issue in the 6 years I've been rather deeply involved with them.

Phil

 

[Raising Arizona]

It's an ongoing debate regards fuse tap orientation, but as a practical matter with dashcams using so little current it doesn't matter. A higher-current draw would matter more. I've never heard of one single case with dashcams where orientation caused any kind of issue in the 6 years I've been rather deeply involved with them.

Phil

I disagree with you on this matter. A dashcam will likely draw about 0.5A or so (500 ma). Although this may seem small, if one were to leave the car parked for say a while ... that is, not start it and drive ... that could be as much a double the normal parasitic current draw for the car. If the car's battery is only so-so, it could easily contribute to a more rapid draining of the battery. And if the car's battery were to drain to say a level of about 10.0 to 10.5 volts, you would be at the threshold where you may not be able to start car. And to the original person's question, there is a possibility that incorrect orientation of a fuse tap could lead to having continuous power on the dashcam.

Steve

 

[Mtrev]

I disagree with you on this matter. A dashcam will likely draw about 0.5A or so (500 ma). Although this may seem small, if one were to leave the car parked for say a while ... that is, not start it and drive ... that could be as much a double the normal parasitic current draw for the car. If the car's battery is only so-so, it could easily contribute to a more rapid draining of the battery. And if the car's battery were to drain to say a level of about 10.0 to 10.5 volts, you would be at the threshold where you may not be able to start car. And to the original person's question, there is a possibility that incorrect orientation of a fuse tap could lead to having continuous power on the dashcam.

Steve

The post you quoted was referring to the minimal draw not causing an issue in overloading the circuit supplying the fuse nothing to do with parasitic drains.
Also the orientation of the fuse tap (which leg is in which side of the fuse) has no impact at all on parasitic drains and whether the dash cam has continuous power. That is dictated by which fuse it is connected to which isn’t the discussion.

 

[Raising Arizona]

The post you quoted was referring to the minimal draw not causing an issue in overloading the circuit supplying the fuse nothing to do with parasitic drains.
Also the orientation of the fuse tap (which leg is in which side of the fuse) has no impact at all on parasitic drains and whether the dash cam has continuous power. That is dictated by which fuse it is connected to which isn’t the discussion.

Actually, what I was replying to was the reply about orientation ... and there are cases where orienting a fuse tap incorrectly could result in drawing continuous power rather than switched power. And if due to incorrect orientation of the fuse tap you are drawing continuous power then you will be contributing to an increase in the parasitic current draw on the car's battery. Yes, a small contribution, but in the grand scheme of things every little bit counts.

Another point is the size of the original fuse you are tapping into. Let's say you decide to tap into a 5A fuse location. If you orient the fuse tap incorrectly, that original fuse will be carrying the existing current load plus whatever load your dashcam draws ... or whatever you decide to put on the fuse tap.

 

[Mtrev]

Actually, what I was replying to was the reply about orientation ... and there are cases where orienting a fuse tap incorrectly could result in drawing continuous power rather than switched power. And if due to incorrect orientation of the fuse tap you are drawing continuous power then you will be contributing to an increase in the parasitic current draw on the car's battery. Yes, a small contribution, but in the grand scheme of things every little bit counts.

Another point is the size of the original fuse you are tapping into. Let's say you decide to tap into a 5A fuse location. If you orient the fuse tap incorrectly, that original fuse will be carrying the existing current load plus whatever load your dashcam draws ... or whatever you decide to put on the fuse tap.

If the fuse tap is in a permanent fed fuse it will draw permanent power regardless of the orientation, if it’s in a switched fuse it will draw switched power regardless of the orientation.

The only difference orientation has is your last paragraph, that’s exactly what the post you replied to was about.
Putting both loads through the original fuse better protects the circuit from overloading but in the case of a dashcam the extra load is so small it doesn’t matter. Better to overload a 5A fuse than the wiring or ecu that supplies it.

 

[md70Yesh]

there are cases where orienting a fuse tap incorrectly could result in drawing continuous power rather than switched power.

I am struggling to understand how that might happen.. Tap-a-fuse is not a relay. Could you give an example?

If you orient the fuse tap incorrectly, that original fuse will be carrying the existing current load plus whatever load your dashcam draws ... or whatever you decide to put on the fuse tap.

Agree, but I am not sure if I would call it "incorrect", it depends on the application. Suppose you put it in "correct" orientation and the original fuse was designed for let's say 10A load. You go ahead and insert a tapped fuse for your secondary device that also consumes 10A. Neither of the fuses will blow when loads are powered on simultaneously because each fuse only caters to its own device. But the input wiring is probably not designed for 20A combined load. Of course as other people already mentioned, dash cams rarely consume more than an amp, so the wiring is going to be just fine.