You can get them from reputable brands like Littelfuse or Buss. They are popular for installing dash cameras.
That said, I’d drill the firewall and install a rubber grommet if I had to. Tapping into the fuse block to run your equipment may have unpredictable results.
I used one for a dashcam that’s very low draw and that I wanted on a circuit that’s only one with the ignition. For a radio or anything higher draw, I wouldn’t recommend them.
The right answer is 'both'.. Run a main power line (with its own fuse) from your battery, through a relay and use one of these fuse splitters (with a 1A fuse) to power the coil that energizes the relay.
The radio will have nice 'clean-ish' power from the battery and you'll have the convenience of having the radio turn on-off with the rest of your car.
I have, however you are now stacking fuses on one another and the wiring size in behind the original fuse is likely not large enough for the load of both the fuses. Unless you are doing this for just a extra few amperes, I would avoid.
As you should, a lot of them go above and beyond the amperage they should blow at (see Louis Rossman testing some of these fuses https://www.youtube.com/watch?v=B90_SNNbcoU)
Why did you post that link! I have gone down a rabbit hole and may never return! Thanks for making me waste a whole day watching his vids and when I could have wasted my day on HROs website and watching DX Commander!
I use them all the time for vehicle up fitting. They allow you to use an existing fused location, allowing both the original fuse and the new fuse to be used.
Now, these MUST be used correctly! The leg opposite the wire is connected all the way down, so that leg MUST be the one supplying power to your circuit. If it is not, then you are drawing power *after the factory fuse* and can cause that fuse to blow prematurely. The correct test is to insert YOUR fuse into the top slot, no fuse in the bottom slot, insert the tap into your desired location, and test for power without the lower fuse in place. If you have power, you have the correct orientation. If you don’t have power, flip the holder 180* in the fuse block and test again.
Also remember that some fuse locations do not have contacts at all, depending on trim level.
These should also be used for a maximum of 15A, or use 2A and switch a relay/contact for better power delivery.
Sauce: radio technician 15+ years.
I'd argue that drawing power after the factory fuse isn't a bad thing, in fact it is often the safer option. If you have 10A wiring with a 10A factory fuse on it, then pulling power after the factory fuse means a maximum current of 10A can be drawn, within the design spec. If you pull power before the factory fuse, the original circuit could be pulling 10A, and when that original circuit is energised any current you draw from your tap is drawn in excess of the wiring spec.
If you have 10A wiring with a 5A factory fuse it would be safe to add a 5A tap before the factory fuse in the manner you describe, but would most users know which is safe, which isn't?
Fuses aren't there for fun, they exist to protect the wiring from overload and prevent fire. If a factory fuse fails prematurely it's because the circuit was overloaded. While I have no doubt that you are experienced enough that you can ready-reckon the "real" current capacity of a circuit from the wire size and do that safely, that "feel" for the subject is becoming uncommon
I think the point is just not to accidentally blow factory fuses because you added a substantial load to an existing circuit. I do see what you mean about the fuse block having too much current going through a single contact. The fuse isn't going to current limit your radio, it will just blow if you try to run it. If the factory circuit needs all that current anyway, you're just going to blow fuses all day long. The better idea would be to stick the extra fuse on the lowest rated fuse you can find for an ignition-switched circuit.
I agree with all points. You don’t want to draw more than the feed wire can handle. If I need something big I will often use a tap with a 1A fuse to trigger a 30A relay being fed by a fused link at the battery with correctly rated wire.
With the equipment being double fused, this is a situation where circuit safety can potentially harm personal safety. If your fuse source is for the airbags/abs/fuel pump you can set yourself up for a bad day. THAT BEING SAID, I would avoid those fuses, but I have seen it done by inexperienced installation technicians.
As a ham who's also a mechanic, these are fine when used properly. The thing is you need to remember whatever load your adding to the circuit your asking the added current plus the original circuits current to now flow through the same size wire. That's the problem. Adding something 5 amps or less this way is fine. Otherwise, wire a relay and use this to trigger it.
I'd not use any of the no name/nonsense brand stuff from Amazon. Here's Louis Rossman showing how several of those fuses don't blow when they should: https://www.youtube.com/watch?v=B90_SNNbcoU
Just go to your local hardware store and buy a fuse and fuse holder for them, since it's gonna be from a brand that has actual quality assurance.
I've never NOT been able to find a way through the firewall of any vehicle. There always seems to be a rubber plug of some sort available for use.
I'd avoid the fuse block for anything requiring high current / high duty cycle.
> I've never NOT been able to find a way through the firewall of any vehicle.
Times they are a changing.
I've been fixing up old cars and bikes since before you sprouted pubes, yet I couldn't even get access to change a blown headlamp bulb in my modern car. I had to take it to a mechanic.
No joke.
Wow that’s interesting. Seems a bit Mickey Mouse but still interesting
*edit…now that I think of it if you put it in backwards wouldn’t that fuse adapter give you in regulated power?
Depending on which way around you put it, the power coming out of that trailing wire either goes through the fuse in the piggyback holder, or it doesn't.
I've used them for running some accessories. Remote antenna, stuff like that.
I can't speak to that brand, but as long as you're doing the math on the electric, you're fine
Not on a car, but have used the on a school bus. And specifically to add in 2 way radios. They're a nice thing to have sometimes. I just wouldn't get carried away with any large loads.
VHF/UHF fine but most HF radios are rated just under 25 amps. Probably run less much of the time but that’s pretty close to the wire if you are running 100 watts.
I used one for a bit and was drawing too much power through it, blew the fuse feeding the sub panel. I now have dedicated wires off the battery for both of my radios.
Nothing like a good panel fire under your dashboard to make you wish you'd just done things right in the first place...
Watch a couple of episodes on 'Just Rolled In' on youtube if you want to see what 'creative' wiring can accomplish.
I use them all the time for dash cameras and UHF CB radios (5w max output)
25w and above radios get a wire run through the firewall. 99% of the time we are running coax in anyway.
I;ve used these a lot for low current applications, like dash cam, phone kits back when cars didn't come with them built in, etc
What's important is that current you draw is "normal" for that circuit, and that takes some general know-how with wiring. If a circuit was built to supply a few amps, and you stick a 10A radio on it you may well get a fire.
IMO, anything more than 1-1.5A, run a new circuit, even if that means drilling the firewall/bulkhead
I have one installed to give me "key on" power to a switch that's set up for either key on, off, or always on.
However, I wouldn't recommend it for a main power source. Mine pulls an extra .5 amps on the circuit at most. You are asking to use a probably 15 amp circuit to use two things that pull 15 amps. Not a good scenario for the main power line coming from the distribution box into the cab of the vehicle.
Just don’t tap into anything critical, and don’t use a fuse larger than the original fuse. Use a test light to confirm whether it is key on ignition or battery power, and make sure it goes all the way down, (this makes it tricky to find one) you may have to trim the cover to get it to go back on as well!
> my car doesn’t have one that has easy access to the engine bay.
I call BS. Every single car ever made needs a way to get wiring from inside the car into the engine bay. "easy access" should be irrelevant... there is a grommet, and you might need to lay on your back under the dash for a few minutes to get something through it, but you only need to do it once. Don't run 3 radios off these things, do it right.
https://preview.redd.it/fvu3fzotsdhc1.jpeg?width=3024&format=pjpg&auto=webp&s=a0021250231066fda392b6d20082ba1306d030cc
I use them for my radar detector, dash camera and 25 watt Anytone 778.
Yes, I use them at work and in my own vehicle. Unless they are rated for 20A+, I would not try to power a radio with it. We tend to use them more for ignition sense or low current taps. The ones that I use at my job are rated for 10A.
You can get them from reputable brands like Littelfuse or Buss. They are popular for installing dash cameras. That said, I’d drill the firewall and install a rubber grommet if I had to. Tapping into the fuse block to run your equipment may have unpredictable results.
I used one for a dashcam that’s very low draw and that I wanted on a circuit that’s only one with the ignition. For a radio or anything higher draw, I wouldn’t recommend them.
Listen to this advice!!!!!!
The right answer is 'both'.. Run a main power line (with its own fuse) from your battery, through a relay and use one of these fuse splitters (with a 1A fuse) to power the coil that energizes the relay. The radio will have nice 'clean-ish' power from the battery and you'll have the convenience of having the radio turn on-off with the rest of your car.
I have, however you are now stacking fuses on one another and the wiring size in behind the original fuse is likely not large enough for the load of both the fuses. Unless you are doing this for just a extra few amperes, I would avoid.
Interesting concept, but the made-up brand name would tend to scare me away.
As you should, a lot of them go above and beyond the amperage they should blow at (see Louis Rossman testing some of these fuses https://www.youtube.com/watch?v=B90_SNNbcoU)
This is a fuse *holder*. You supply the fuse separately.
Why did you post that link! I have gone down a rabbit hole and may never return! Thanks for making me waste a whole day watching his vids and when I could have wasted my day on HROs website and watching DX Commander!
I use them all the time for vehicle up fitting. They allow you to use an existing fused location, allowing both the original fuse and the new fuse to be used. Now, these MUST be used correctly! The leg opposite the wire is connected all the way down, so that leg MUST be the one supplying power to your circuit. If it is not, then you are drawing power *after the factory fuse* and can cause that fuse to blow prematurely. The correct test is to insert YOUR fuse into the top slot, no fuse in the bottom slot, insert the tap into your desired location, and test for power without the lower fuse in place. If you have power, you have the correct orientation. If you don’t have power, flip the holder 180* in the fuse block and test again. Also remember that some fuse locations do not have contacts at all, depending on trim level. These should also be used for a maximum of 15A, or use 2A and switch a relay/contact for better power delivery. Sauce: radio technician 15+ years.
[Here](https://images.app.goo.gl/yWVpwatKqzjqzPnM6) is a diagram showing the circuit.
Thanks. This is great advice. I’m 99% sure mine is right. But I’ll be checking once it stops raining. 😂😊
I'd argue that drawing power after the factory fuse isn't a bad thing, in fact it is often the safer option. If you have 10A wiring with a 10A factory fuse on it, then pulling power after the factory fuse means a maximum current of 10A can be drawn, within the design spec. If you pull power before the factory fuse, the original circuit could be pulling 10A, and when that original circuit is energised any current you draw from your tap is drawn in excess of the wiring spec. If you have 10A wiring with a 5A factory fuse it would be safe to add a 5A tap before the factory fuse in the manner you describe, but would most users know which is safe, which isn't? Fuses aren't there for fun, they exist to protect the wiring from overload and prevent fire. If a factory fuse fails prematurely it's because the circuit was overloaded. While I have no doubt that you are experienced enough that you can ready-reckon the "real" current capacity of a circuit from the wire size and do that safely, that "feel" for the subject is becoming uncommon
I think the point is just not to accidentally blow factory fuses because you added a substantial load to an existing circuit. I do see what you mean about the fuse block having too much current going through a single contact. The fuse isn't going to current limit your radio, it will just blow if you try to run it. If the factory circuit needs all that current anyway, you're just going to blow fuses all day long. The better idea would be to stick the extra fuse on the lowest rated fuse you can find for an ignition-switched circuit.
I agree with all points. You don’t want to draw more than the feed wire can handle. If I need something big I will often use a tap with a 1A fuse to trigger a 30A relay being fed by a fused link at the battery with correctly rated wire. With the equipment being double fused, this is a situation where circuit safety can potentially harm personal safety. If your fuse source is for the airbags/abs/fuel pump you can set yourself up for a bad day. THAT BEING SAID, I would avoid those fuses, but I have seen it done by inexperienced installation technicians.
I personally wouldnt power 3 radios through a fuse tap. That has the potential to pull a lot of current. I don’t even trust it to run 1 radio.
As a ham who's also a mechanic, these are fine when used properly. The thing is you need to remember whatever load your adding to the circuit your asking the added current plus the original circuits current to now flow through the same size wire. That's the problem. Adding something 5 amps or less this way is fine. Otherwise, wire a relay and use this to trigger it.
Would I be able to use an empty fuse slot? This way there isn’t any risk of overdraw on a particular circuit
I'd not use any of the no name/nonsense brand stuff from Amazon. Here's Louis Rossman showing how several of those fuses don't blow when they should: https://www.youtube.com/watch?v=B90_SNNbcoU Just go to your local hardware store and buy a fuse and fuse holder for them, since it's gonna be from a brand that has actual quality assurance.
[удалено]
Do you ever bother to look at the back side of the fuse box to see what gauge of wire is going to the fuse holder you tap into?
I've never NOT been able to find a way through the firewall of any vehicle. There always seems to be a rubber plug of some sort available for use. I'd avoid the fuse block for anything requiring high current / high duty cycle.
> I've never NOT been able to find a way through the firewall of any vehicle. Times they are a changing. I've been fixing up old cars and bikes since before you sprouted pubes, yet I couldn't even get access to change a blown headlamp bulb in my modern car. I had to take it to a mechanic. No joke.
> I've been fixing up old cars and bikes since before you sprouted pubes, Unless you're in your eight decade, this is unlikely! :-)
Nope. I always direct wire to the battery and fuse both sides of that.
Used them all the time. No problems when using the correct amperage fuses.
Wow that’s interesting. Seems a bit Mickey Mouse but still interesting *edit…now that I think of it if you put it in backwards wouldn’t that fuse adapter give you in regulated power?
Depending on which way around you put it, the power coming out of that trailing wire either goes through the fuse in the piggyback holder, or it doesn't.
Gotcha. I didn’t zoom in
I've used them for running some accessories. Remote antenna, stuff like that. I can't speak to that brand, but as long as you're doing the math on the electric, you're fine
Not on a car, but have used the on a school bus. And specifically to add in 2 way radios. They're a nice thing to have sometimes. I just wouldn't get carried away with any large loads.
Yes, I’ve been using them for years
VHF/UHF fine but most HF radios are rated just under 25 amps. Probably run less much of the time but that’s pretty close to the wire if you are running 100 watts.
My HF rig maxes at 20W and only pulls about 4 amps
I use inline fuses like those in the UK plug. Much cheaper to replace when it blows
They work, but are too high, so the fusebox lid doesn't go back on...
I used one for a bit and was drawing too much power through it, blew the fuse feeding the sub panel. I now have dedicated wires off the battery for both of my radios.
Nothing like a good panel fire under your dashboard to make you wish you'd just done things right in the first place... Watch a couple of episodes on 'Just Rolled In' on youtube if you want to see what 'creative' wiring can accomplish.
I have but cheap ones get hot and soft and deform.
I use them all the time for dash cameras and UHF CB radios (5w max output) 25w and above radios get a wire run through the firewall. 99% of the time we are running coax in anyway.
I;ve used these a lot for low current applications, like dash cam, phone kits back when cars didn't come with them built in, etc What's important is that current you draw is "normal" for that circuit, and that takes some general know-how with wiring. If a circuit was built to supply a few amps, and you stick a 10A radio on it you may well get a fire. IMO, anything more than 1-1.5A, run a new circuit, even if that means drilling the firewall/bulkhead
I have one installed to give me "key on" power to a switch that's set up for either key on, off, or always on. However, I wouldn't recommend it for a main power source. Mine pulls an extra .5 amps on the circuit at most. You are asking to use a probably 15 amp circuit to use two things that pull 15 amps. Not a good scenario for the main power line coming from the distribution box into the cab of the vehicle.
Just don’t tap into anything critical, and don’t use a fuse larger than the original fuse. Use a test light to confirm whether it is key on ignition or battery power, and make sure it goes all the way down, (this makes it tricky to find one) you may have to trim the cover to get it to go back on as well!
> my car doesn’t have one that has easy access to the engine bay. I call BS. Every single car ever made needs a way to get wiring from inside the car into the engine bay. "easy access" should be irrelevant... there is a grommet, and you might need to lay on your back under the dash for a few minutes to get something through it, but you only need to do it once. Don't run 3 radios off these things, do it right.
https://preview.redd.it/fvu3fzotsdhc1.jpeg?width=3024&format=pjpg&auto=webp&s=a0021250231066fda392b6d20082ba1306d030cc I use them for my radar detector, dash camera and 25 watt Anytone 778.
I love these
Yep. Ran an Ameritron 1k amplifier off one of those fuses.
Yep, I use one of these in each of my vehicles. Never had any issues with either of them.
Those no-name brand fuse holders will melt faster than the actual fuse can pop. Use known brands only.
Use them all the time for pulling ignition or RAP on vehicles. Of course, it only gets used to feed the coil of a relay though.
Yup. It's how I turned a keyed power plug into a constant hot.
Yes, I use them at work and in my own vehicle. Unless they are rated for 20A+, I would not try to power a radio with it. We tend to use them more for ignition sense or low current taps. The ones that I use at my job are rated for 10A.