I am talking about this type of fuse block. Its really meant for marine applications that do not have a chassis ground. This type of fuse block appeals to me because of the layout and the ring terminal screw type connections.(the LEDs indicating a blown fuse are also a nice bonus) but I can only find this configuration in a negative bus bar setup which I have never used because the things I am adding fuses and relays to all have a chassis ground and I am not going to run miles of extra wire just to ground it to the built in bus bar.
So my question is can I use this type of fuse box and simply ground the negative bus bar to the chassis to complete the circuit? Usually I just use in-line fuses(or fuse blocks) so this type has me confused and unsure if what I am thinking will work actually does. I really wish that in-line blocks had nice little ring terminal connections and a compact square configuration like this...but they don't.
Yes. I recommend the blue sea versions on amazon.
These are just fancy and water resistant fuse blocks. Meant for a 12V system just like a car, no need to use the ground bar. Heck, I didnt use the integrated ground bar when I installed it in my BOAT. Used a seperate ground bar connected to negative batter terminal for reducing wire complexity.
In reply to Olemiss540 :
But it does still need to be grounded through the ground stud at least I would assume? Just trying to get an idea what wiring in line with a relay looks like for the fuel pump circuit as an example.
ECU output>Relay Pin 86>Fuse Box Ring terminal #1>Bus bar ring terminal>ground?
Assuming that the negative side of the battery is connected to the chassis somewhere you can connect the ground buss on the fuse block to the chassis and then any circuit can be grounded at either the chassis or the buss bar.
I actually used that fuseblock (or one ridiculously similar) when fixing a POs wiring on a buddies Audi90. I grounded the main negative stud to the chassis and then used the negative bar for the specific accessories like your 'flowchart'.
In reply to iansane :
I was just confused since I have to include relays in the circuits and if you have the fuses before the relays and wire it like that, the output of say the fuel pump fuse is going to energize the fuel pump, the headlights, and the main power relays all at once...things like that, so the fuses would have to be installed downstream of the relays correct?
P.S. wait, I see that would not be the case since the input side of those other fuses would still have to be energized to complete the circuit for those other accesories.
Wicked93gs said:
In reply to iansane :
I was just confused since I have to include relays in the circuits and if you have the fuses before the relays and wire it like that, the output of say the fuel pump fuse is going to energize the fuel pump, the headlights, and the main power relays all at once...things like that, so the fuses would have to be installed downstream of the relays correct?
P.S. wait, I see that would not be the case since the input side of those other fuses would still have to be energized to complete the circuit for those other accesories.
Fuses should always be as close to the power source as possible and really there should be a fusible link, circuit breaker or even a big ass fuse at the battery in the wire going to the fuse box.
Going back to your original example with the fuel pump relay I want to check on another potential source of confusion. Not all ECU outputs are active high (+12v out to turn on). Depending on the circuit and the ECU some can be active low (0v, or pulled to ground to turn on).
If the output is active high then it's ECUoutput -> Relay Pin 86 -> Relay pin 85 -> Ground (either chassis or buss bar) and you're relying on the ECU's internal protection. If it's active low then it's Fused 12V->Relay Pin 86 -> Relay Pin 85 -> ECU output.
Whichever control scheme is used the other side of the relay is Fused 12V->Relay Pin 87 -> Relay Pin 30 -> Fuel pump.
In reply to APEowner :
Thank you, that clarifies it, ECU is MS3, which I can't remember if its ground or power output for fuel pump, need to research that and the fan output before I start wiring all this mess of stuff up. I currently have a fuse and relay box I wired up, but I really don't like the result and how difficult it is to pull things out the change them around. SO I plan on using a positive and negative bus bar, this fuse block, individual relays and a couple terminal blocks so its just a matter of making different size ring terminal wires and screwing and unscrewing them as needed.
Wicked93gs said:
In reply to APEowner :
Thank you, that clarifies it, ECU is MS3, which I can't remember if its ground or power output for fuel pump, need to research that and the fan output before I start wiring all this mess of stuff up. I currently have a fuse and relay box I wired up, but I really don't like the result and how difficult it is to pull things out the change them around. SO I plan on using a positive and negative bus bar, this fuse block, individual relays and a couple terminal blocks so its just a matter of making different size ring terminal wires and screwing and unscrewing them as needed.
Glad to help. I highly recommend taking the time to draw out a schematic before you actually start wiring. It's a lot of work but it allows you to catch things early in the process and cuts down on the amount of rework needed.
I can confirm that using a fuse box like that for just the positive side of the circuits and grounding to the chassis works just fine. That's how I'm wiring the accessories on my truck.
thatsnowinnebago said:
I can confirm that using a fuse box like that for just the positive side of the circuits and grounding to the chassis works just fine. That's how I'm wiring the accessories on my truck.
I installed one like this for my car in the same manner. Works well.
So the fuse box came in today...I took the opportunity to take the back off to see exactly what I was working with. The positive large terminal connects to a common positive bus-bar for all the fuses. The negative large terminal connects to a negative bus-bar that connects to nothing. IE, the negative bus-bar is literally just a grounding point(assuming you connect the large terminal to ground or battery negative). It clarifies a lot in my mind
So based on everything I understand, my wiring should be as follows(note that this is just a generic diagram based on a power switched relay, not ground switched). Since the ground bus-bar isnt connected to anything, any wires I have running there should theoretically be able to be grounded anywhere on the chassis or the battery negative terminal. This should work correct? I will likely try it later today with some jumper wires and see if I can get the relay to trigger.
My diagram was right...but the wire colors coming from my relay sockets were wrong, so it confused me as to why it wouldn't work. But then I rewired the sockets with 12 gauge wiring for everything but the inputs(which went to 14 gauge). Why in the world would you have a 40 amp relay, but only have 16 gauge wiring supplying it? Complete nonsense that had to be fixed.
In reply to Wicked93gs :
My guess is because even though the relay is a 30 or 40 amp relay, its fed by a 10, 15, or 20 amp fused power source so it will never see 40 amps without the fuses power failing. No need for 12 gauge wire running a 15 amp circuit.
In reply to Olemiss540 :
Sure...but 16 gauge wire is good for 13 amps. If you are running a relay for a circuit, by definition you are needing to draw more than that, otherwise you can get away with just a fuse...for example...I have 6 relays here: Low beam headlights(at least 15 amps with incandescent bulbs)m High beam headlights(same), Electric Fan(30 amps), Electric Fuel Pump(anywhere between 7 and 20 amps depending on age and flow), Starter solenoid(up to 30 amp spikes), and Main Power that supplies power to blinker, interior lights, fog lights, radio, ECU, etc. 16 gauge wiring is nearly worthless for ANY of those circuits aside from maybe the fuel pump...but you need higher gauge wiring to supply a fuel pump even so if you want it running at full efficiency, all of these circuits will get 20-30 amp fuses supplying the relays with individual accessories having further fuses in-line after the relay powered through the interior fuse box(IE, the ECU, which gets a 2 amp fuse to protect it). So the fact remains...if you are using a relay, you need better than 16 gauge wiring unless you are strictly using it as a trigger on an ECU output instead of an actual switch of some sort.
I don't understand how using a relay and using a fuse are interchangeable, only dependent on load.
A relay is an electrically controlled switch. I have relays controlling five amp circuits. I couldn't replace it with a fuse, because then it would not be controlled anymore.
Wire gauge has a lot to do with length as well as current. I used to run 10 gauge wire to power amplifiers that would draw a peak of ten amps.
In reply to Pete. (l33t FS) :
You are looking at this through the lens of a modern car. My project in particular is a '66 Mustang and while I do have an EFI engine swap, the ECU only switches on the fan and the fuel pump...and technically no ECU or relay is needed to control either circuit. Let me give you this example: Headlights. In 1966 Ford didn't use ANY relays(unless you consider a starter solenoid a relay). Current for the headlights was routed through the headlight switch through 14 gauge wiring...what that means is that it has 15% voltage drop by the time it runs from the battery, to the headlight switch, then back to the headlights....all the while being on the verge of overloading the wiring. Now, lets add a relay with 12 gauge wiring feed to the headlights instead: That same circuit only has a voltage drop of 2%. Voltage drop is a serious issue and reducing the length of the current carrying wire and increasing the size will hugely reduce the drop. In the case of headlights, this means 13% brighter headlights when adding a relay with 12 gauge wiring...in the case of an electric fan, this means 13% more air moved, a fuel pump max flow will increase as well(though not by 13% since the wiring run is longer regardless...but still a voltage increase of 10% compared to 14 gauge wiring). Relays are NOT just electronic switches...though they can be used as such...their main purpose is to reduce voltage drop and take load off of things like ignition switches, headlight switches, etc.(in my example of a 66 mustang, you have parking lights, headlights, horn, and interior lights all run through the poor abused headlight switch...that's a LOT of amps, its a good thing that those switches were built tough)
There are plenty of non-ECU types of switches, from toggles to temperature switches to ignition switches etc that will do the job just fine without a relay...the purpose of the relay as a switch-only applies strictly to vehicles that those circuits are controlled by the ECU, and that is because the ECU simply can't handle the load those circuits draw(there are some exceptions to that rule...but circuit board traces dont hold many amps before frying)
Anyway, everything I am using a relay for uses at least 15 amps at peak draw...which means 16 gauge wires feeding a relay are worthless and a fire hazard.
In reply to Wicked93gs :
Okey dokie. Work looks great and congrats! Was just replying to: "Why in the world would you have a 40 amp relay, but only have 16 gauge wiring supplying it" but sounds like you got her handled. Nothing wrong with overkill on using 12 ga for both power and switch sources and every other wire in the car if it floats your boat.
In reply to Olemiss540 :
Heh, there is a certain amount of overkill to my wiring(IE, aside from the ECU and engine harness everything is at least 14 gauge now) but not having a large enough gauge wire to supply the peak draw is asking for a fire. I am actually worried about the positive and negative bus bars in the fuse block itself being able to handle the peak amperage draw of headlights, main power, fuel pump, and fan all at one time...that can be up to 80 amps...which is why the battery feed and ground wires are doubled up 10 gauge wiring...and that is only good for 60 amps sustained, so there is still room for more overkill....or possibly convert to LEDs wherever possible to reduce the load down below 60 amps.
Sounds like you got it handled.
In reply to Wicked93gs :
Yah, I'm looking through the lens of assuming that the switches are not engineered for high current.
although, really, everything WOULD benefit from being relayed, even on those. Have measured some righteous voltage drops through the ignition switch on cars from before the "control module all the things!" era.
Wicked93gs said:
... I am actually worried about the positive and negative bus bars in the fuse block itself being able to handle the peak amperage draw of headlights, main power, fuel pump, and fan all at one time...that can be up to 80 amps...
There should be a power or current rating for the whole fuse block somewhere.
