Orientation of the Fuse Tap into Fuse Box?

thethreegs

New Member
Joined
Jul 10, 2021
Messages
7
Reaction score
2
Location
California
Country
United States
(1) As I understand it, I need to test which side of the fuse insert shows 12 volts. I am supposed to insert the blade that is furthest from the cable into the side that shows 12 volts. Is this the correct way to install and orientate the fuse tap?

(2) Does it matter which way the new fuse and the original fuse are inserted into the fuse tap? I know the original fuse is supposed to be inserted into the slot nearest the blades but does it matter which way it goes in?

(3) What are the most common fuses to use for continuous power and only when turned on? Only turned on, should I use the cigarette lighter and continuous use an interior light? I have a 2014 Hyundai Elantra GT for reference, if that even matters.
 

kamkar

Well-Known Member
Joined
Oct 11, 2013
Messages
30,426
Reaction score
17,103
Country
Denmark
Dash Cam
10 years, many dashcams
Welcome to the forum.

I must admit i never bothered with what side of the fuse was the live one when i have hard wired cameras, could be i have just been lucky cuz the 2 times i have tried it have worked just fine.

I have put 5A fuses in my fuse tab, and i am running 2 systems off that, though only the one are used in parking guard, this is a 3 channel viofo camera and a 2 channel street guardian system.
The fuse i am riding are just a 10 A one as i recall.
 

SawMaster

Well-Known Member
Joined
Apr 10, 2015
Messages
9,098
Reaction score
7,925
Location
SC
Country
United States
Dash Cam
Numerous and ever-changing
2- In theory there is a best way to orient a fuse tap for a dsahcam. In practice the current being drawn is so small that it doesn't matter :cool: I've not heard of a single person having problems doing it either way, but if you're tapping for a device with a higher current draw then it does matter.

3- Each car differs and many cars today use computer-controlled power schemes which drop power to certain circuits after a delay time, making general recommendations tough. Always avoid safety-related circuits like air bags (SRS), ABS, ECM/PCM (engine computers) and exterior lighting. Some good chances for always-on power are cigarette lighter or power ports, power unlocking, and the secondary for the radio which operates it's clock and memory.

Phil
 

rcg530

Active Member
Joined
Jan 23, 2021
Messages
62
Reaction score
111
Location
California
Country
United States
Dash Cam
Thinkware, VIOFO, BlackVue, Blueskysea
(1) As I understand it, I need to test which side of the fuse insert shows 12 volts. I am supposed to insert the blade that is furthest from the cable into the side that shows 12 volts. Is this the correct way to install and orientate the fuse tap?
Yes, the blade / leg that is furthest from the wire (left leg) is the one that should receive the power from the fuse box fuse socket. If the right leg gets the power from the fuse box fuse socket, it's routing the power through the lower fuse and then through the upper fuse to the new accessory (dash camera in this case). It's a general good practice to make sure you're inserting the left leg of the fuse tap into the side of the fuse box fuse socket that provides the power.

(2) Does it matter which way the new fuse and the original fuse are inserted into the fuse tap? I know the original fuse is supposed to be inserted into the slot nearest the blades but does it matter which way it goes in?
The top fuse socket in the fuse tap is the one that gets the fuse for the new accessory. The bottom fuse socket of the fuse tap gets the fuse that was present in the fuse box fuse socket (if any was present in the fuse box fuse socket).

There is no "directional" aspect to the blade fuse itself.

Here's a video on my YouTube channel that shows how to test for the proper fuse tap orientation in the fuse box fuse socket.

 
OP
thethreegs

thethreegs

New Member
Joined
Jul 10, 2021
Messages
7
Reaction score
2
Location
California
Country
United States
Hey guys - so when I used the multimeter, BOTH sides of any fuse I tested that had any voltage, showed voltage. I thought one side was supposed to show voltage only? How am I supposed to know which way to orientate the fuse tap if BOTH are showing voltage?
 

rcg530

Active Member
Joined
Jan 23, 2021
Messages
62
Reaction score
111
Location
California
Country
United States
Dash Cam
Thinkware, VIOFO, BlackVue, Blueskysea
Hey guys - so when I used the multimeter, BOTH sides of any fuse I tested that had any voltage, showed voltage. I thought one side was supposed to show voltage only? How am I supposed to know which way to orientate the fuse tap if BOTH are showing voltage?
If the fuse box fuse socket has power supplied to it and you test for voltage on either side of the fuse, it will show power on both sides if the fuse is a "good" fuse.

You need to remove the fuse and test for power from the fuse socket itself. I demonstrate a way to easily perform that test in the video I posted a couple of posts back using the fuse tap itself with only a fuse in the top fuse socket of the fuse tap.
 
OP
thethreegs

thethreegs

New Member
Joined
Jul 10, 2021
Messages
7
Reaction score
2
Location
California
Country
United States
If the fuse box fuse socket has power supplied to it and you test for voltage on either side of the fuse, it will show power on both sides if the fuse is a "good" fuse.

You need to remove the fuse and test for power from the fuse socket itself. I demonstrate a way to easily perform that test in the video I posted a couple of posts back using the fuse tap itself with only a fuse in the top fuse socket of the fuse tap.
Thank you, this makes perfect sense.
 

Mtrev

Active Member
Joined
Aug 15, 2020
Messages
209
Reaction score
147
Location
Shropshire
Country
United Kingdom
Yes, the blade / leg that is furthest from the wire (left leg) is the one that should receive the power from the fuse box fuse socket. If the right leg gets the power from the fuse box fuse socket, it's routing the power through the lower fuse and then through the upper fuse to the new accessory (dash camera in this case). It's a general good practice to make sure you're inserting the left leg of the fuse tap into the side of the fuse box fuse socket that provides the power.


The top fuse socket in the fuse tap is the one that gets the fuse for the new accessory. The bottom fuse socket of the fuse tap gets the fuse that was present in the fuse box fuse socket (if any was present in the fuse box fuse socket).

There is no "directional" aspect to the blade fuse itself.

Here's a video on my YouTube channel that shows how to test for the proper fuse tap orientation in the fuse box fuse socket.

Isn’t the argument that if you put the power in on the left leg you have the potential to overload the circuit supplying the fuse?
Like if the original circuit is a 20A you then have a potential 20A draw plus whatever size fuse you put in the top slot.
Using the right leg to route both loads through the original fuse keeps the circuit protected at the level of the original fuse with an additional lower fuse for the new accessory.
 

rcg530

Active Member
Joined
Jan 23, 2021
Messages
62
Reaction score
111
Location
California
Country
United States
Dash Cam
Thinkware, VIOFO, BlackVue, Blueskysea
Isn’t the argument that if you put the power in on the left leg you have the potential to overload the circuit supplying the fuse?
Like if the original circuit is a 20A you then have a potential 20A draw plus whatever size fuse you put in the top slot.
Using the right leg to route both loads through the original fuse keeps the circuit protected at the level of the original fuse with an additional lower fuse for the new accessory.
Yes, you can overload the power source for the fuse box fuse socket if you take it to an extreme.

My approach is you should only use a fuse box fuse socket that obtains power directly from the battery or from the accessory power circuit from the ignition switch (if you can determine how the power is provided to the fuse box fuse socket). Those type of power circuits usually have the thickest gauge wire or use a power distribution/bus bar in the fuse box to obtain their power. IMO, there's no perfect / 100 percent right all of the time answer to this topic without having knowledge of the internals of the fuse box and its power sources for fuse box fuse sockets. Without direct knowledge of how the fuse box is internally designed, adding any fuse tap is something that requires some use of common sense and limits. No auto manufacturer will (officially) endorse the use of any fuse tap in any fuse box for any purpose.

Powering items such as dash cameras or radar detectors which usually require 2 to 5 amps (often less than 1 amp for many single or dual channel dash cameras) is a small incremental load to be added to the circuit. If something requires any sizeable amount of amps (more than 10A), I usually recommend using a relay to provide the power to that accessory. Using a fuse tap to obtain the control circuit side of the relay (very low power draw) and the new accessory's power sourced directly from the vehicle's battery with an appropriately sized inline fuse and appropriately sized wire gauge wire.

If the right leg of the fuse tap is the one that receives power from the fuse box fuse socket, it's being assumed there's enough unused amps in that fuse at all times to power the new accessory. If there was a 20A fuse in the fuse box fuse socket to begin with and you're adding a 5A amp load with the fuse tap, the premise is that there's always at least 5A available at all times (otherwise that fuse would blow frequently). If that were the case, the auto manufacturer very likely would have sized the fuse at 15A instead of 20A.

I prefer to let the original fuse box fuse do its job of protecting the circuit (primarily post fuse box) and only add a small load using the fuse tap with the left leg of the fuse tap providing power to both fuse sockets of the fuse tap.
 

Nigel

Well-Known Member
Joined
Jul 7, 2014
Messages
14,221
Reaction score
7,245
Location
Devon
Country
United Kingdom
Dash Cam
Gitup F1+G3ꞈꞈꞈꞈꞈ Viofo A139ꞈꞈꞈꞈꞈ Blueskysea B4K+B2K
I prefer to let the original fuse box fuse do its job of protecting the circuit (primarily post fuse box)
Then you shouldn’t add an extra fuse bypassing the original! You should connect it as a tap after the original fuse.

In modern cars the fuse is often protecting more before the fuse than after. Assume that the fuse is the correct size to protect the full circuit and that the fuse was rated with enough spare capacity to be able to tap some off for the camera. If it doesn’t have enough spare capacity then you will find out when it blows, you can then sort the problem safely and without having to replace anything expensive like the cars central computer that got overloaded.


Isn’t the argument that if you put the power in on the left leg you have the potential to overload the circuit supplying the fuse?
Like if the original circuit is a 20A you then have a potential 20A draw plus whatever size fuse you put in the top slot.
Using the right leg to route both loads through the original fuse keeps the circuit protected at the level of the original fuse with an additional lower fuse for the new accessory.
Correct :)
 

rcg530

Active Member
Joined
Jan 23, 2021
Messages
62
Reaction score
111
Location
California
Country
United States
Dash Cam
Thinkware, VIOFO, BlackVue, Blueskysea
Then you shouldn’t add an extra fuse bypassing the original! You should connect it as a tap after the original fuse.
My approach is you should only use a fuse box fuse socket that obtains power directly from the battery or from the accessory power circuit from the ignition switch.

In modern cars the fuse is often protecting more before the fuse than after. Assume that the fuse is the correct size to protect the full circuit and that the fuse was rated with enough spare capacity to be able to tap some off for the camera. If it doesn’t have enough spare capacity then you will find out when it blows, you can then sort the problem safely and without having to replace anything expensive like the cars central computer that got overloaded.
You should never use a fuse box fuse socket that obtains its power from a critical control module (ECM, PCM, ABS/EBCM, body control module, etc) or provides power to any control module.

Supplying power only to the right leg of a fuse tap also eliminates the potential use of a unoccupied fuse box fuse sockets.

If a fuse tap is used to obtain power from an unoccupied fuse box fuse socket that still provides power (because that feature / accessory is not present in that particular vehicle), the fuse tap right leg approach would require you to place a fuse in the lower fuse socket of the fuse tap as well as the top fuse tap fuse socket. That's a potential problem because power is now being provided to the other side of the fuse box fuse socket that wasn't getting power before adding the fuse tap. I've seen this approach cause problems such as phantom power draws/drains because power is now being fed back into the fuse box fuse socket which might back feed into other things inside of the fuse box that was not intended to have power (depending on how the power is routed inside of the fuse box).
 

Nigel

Well-Known Member
Joined
Jul 7, 2014
Messages
14,221
Reaction score
7,245
Location
Devon
Country
United Kingdom
Dash Cam
Gitup F1+G3ꞈꞈꞈꞈꞈ Viofo A139ꞈꞈꞈꞈꞈ Blueskysea B4K+B2K
You should never use a fuse box fuse socket that obtains its power from a critical control module (ECM, PCM, ABS/EBCM, body control module, etc) or provides power to any control module
Most people have no way of knowing where the power for a fuse comes from, so connecting the common leg to the source is dangerous. Even Aux can be relay controlled, in my car it gets turned off via relay when starting the engine. That particular relay is not on a PCB but is controlled from one.

For an unused fuse socket, yes it is best not to use both fuses, obviously that is a different situation.
 

rcg530

Active Member
Joined
Jan 23, 2021
Messages
62
Reaction score
111
Location
California
Country
United States
Dash Cam
Thinkware, VIOFO, BlackVue, Blueskysea
I'm not wanting to rehash the fuse tap fuses run "in parallel" vs "in series" discussion thread ( Piggy-back fuseholders - a right way and a wrong way? ) that lasted over several years.

Both approaches have their pluses and minuses.

The "in series" approach (power to the right leg of the fuse tap):
  • It will provide the most protection to the upstream power feed to the fuse box fuse socket
  • It may cause the original fuse to blow if the power demands of the original circuit are close the the original fuse amp rating
    • The additional load from the new device/accessory pushes the total amp load over the amp rating of the original fuse causing it to blow
    • To diagnose:
      • You will need to remove the fuse tap or at least the upper fuse in the fuse tap for the new accessory to see if it was the extra load causing the original fuse to blow
        • If the original device/accessory fuse blows again with the fuse tap removed or disabled
          • You need to track down the problem with the original device/accessory circuit.
        • If the original device/accessory fuse doesn't blow again with the fuse tap removed or disabled
          • You need to potentially relocate the fuse tap to a different fuse socket
  • Can result in the new device/accessory to lose power when not required - or at in inopportune time
    • If the original circuit has a problem in the device/accessory/wiring requiring it to legitimately blow the original fuse
    • Two circuits lose power when only one needed the fuse to blow due to the problem with the original device/accessory/wiring.
The "in parallel" approach (power to the left leg of the fuse tap):
  • Provides power directly to both fuses
    • This is the core of the debate
    • If the original circuit blows its fuse for a legit problem, you still maintain power to the new device/accessory
      • This can be beneficial in situations like an accident has occurred and the original circuit has been compromised blowing the original fuse only.
      • This allows the new device/accessory (a dash camera?) to continue to operate. A small benefit, but it might be an important one depending on the situation (car accident).
  • You do lose the extra "protection" of having the original fuse blow if the total amp draw for both circuits (original and new) exceeds the amp rating of the original fuse
    • That's why I suggest obtaining power
      • For unswitched/constant power: from a fuse powered directly from the battery and/or a bus bar in the fuse box
      • For switched/accessory power: directly from an ignition switch controlled circuit or a relay controlled by the ignition switch (likely through a bus bar as well)
    • Never use a fuse box fuse socket the obtains power from a control module or provides power to a control module
      • Never tap into a fuse socket for critical control systems (ECM, PCM, ABS, BCM, SRS [Airbag], etc).
      • If there's a computer module involved in that circuit - avoid it.
    • Never use a fuse for the new device/accessory that has an amp rating higher than required
      • If you're powering a dash camera, you likely will never need a fuse with an amp rating over 2A or 3A.
      • Even a 1A fuse might be sufficient, but my testing has found that many 1A fuses really don't blow until 2A or 3A is applied, so I usually stick with 2A or 3A fuses.

I've used the "in parallel" approach of installing fuse taps for a very long time, but I do my research on what I'm tapping into in the fuse box and use appropriately sized fuses and wires.

Please understand the pluses and minuses of each approach and decide which approach is appropriate or necessary in your vehicle's and device's installation.
 

SawMaster

Well-Known Member
Joined
Apr 10, 2015
Messages
9,098
Reaction score
7,925
Location
SC
Country
United States
Dash Cam
Numerous and ever-changing
With the small current draw of dashcams, orientation of fuse taps is rather academic but it is important in higher-current applications. In the 6+ years of me being deep into dashcams I have never heard of anyone anywhere having a problem with the fuse tap run either way, so I say don't worry about it. Let the OCD sufferers lose sleep over it, just plug it in however you like and go :cool:

Phil
 
Top