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Hey guys new here and I am trying to wire up my electrical system with relays.
I purchased a sweet custom toggle switch board with built in 15amp breakers and now i'm left scratching my head on how to properly wire my relays, with the switch and the accessory; LED bar, fuel pump, trans fan.... you name it. Any and all help is appreciated!!!
I have a small circuit drawing, is this correct?
There are two main power strips that receive power on the switch panel. The power flows to the 15 amp and then to the switch. I have power coming into the main power line on the switch board. I then route the switch wire to the relay pin 86, pin 87 goes to accessory and grounds out. Pin 85 routes to ground. Pin 30 would also have power coming to it from a fused connection to the battery. Is this correct? It appears to me that I have two power feeds and I'm not sure that's a proper circuit.
Thanks and please let me know what questions you have that would help me sold or if you need more pics.
Last edited by WhiteBird00; Jun 10, 2019 at 11:22 AM.
From: Jacksonville, FL (originally from Toronto Canada)
Your schematic of the relay connections is correct. Power to pin 86 flows through the electromagnet coil of the relay to ground via pin 85, When that current flows (switch is on), the relay activates and allows power from pin 30 to flow through pin 87 to whatever device you have connected - in this case the ECM.
My question is why would you use a relay in this situation. The ECM draws less than 15 amps of power (the factory configuration has it on a 15 amp fuse) and both your switch and wiring (looks like 16 gauge or larger) will handle that much current easily. Adding a relay just creates another possible point of failure in the circuit.
There are three common uses for relays... to control a high current circuit with a low current trigger, to control a constant (unswitched) current source with an ignition switched trigger, or to reverse polarity of a circuit. Yours could only fall into the first category except that the ECM is not a high current circuit. There's nothing wrong with simply running your switch output directly to the ECM - it achieves the same result without an extra component that could fail.
Your schematic of the relay connections is correct. Power to pin 86 flows through the electromagnet coil of the relay to ground via pin 85, When that current flows (switch is on), the relay activates and allows power from pin 30 to flow through pin 87 to whatever device you have connected - in this case the ECM.
My question is why would you use a relay in this situation. The ECM draws less than 15 amps of power (the factory configuration has it on a 15 amp fuse) and both your switch and wiring (looks like 16 gauge or larger) will handle that much current easily. Adding a relay just creates another possible point of failure in the circuit.
There are three common uses for relays... to control a high current circuit with a low current trigger, to control a constant (unswitched) current source with an ignition switched trigger, or to reverse polarity of a circuit. Yours could only fall into the first category except that the ECM is not a high current circuit. There's nothing wrong with simply running your switch output directly to the ECM - it achieves the same result without an extra component that could fail.
Thank you for that help. I understand your response and your advice is good. I will not put in a circuit with less than 20 amps. Stupid question... how do i figure out how many amps a circuit will draw?
This is where i am now: Built out a circuit board to host 5 relays and two fuse banks. Relay 1,2 and 3 will go to three panels with switches. Each relay will power 1 row of switches on the panel. The switches will operate devices (ECU, Fuel Pump, Gauges, Head Lights, Turn signals, dome light........) Each toggle has a 20 amp breaker on it. I'm assuming that will work as I believe this falls within the first two you mentioned, " high current circuit with a low current trigger, to control a constant (unswitched)".
Last edited by WhiteBird00; Jun 10, 2019 at 11:56 AM.
Your schematic of the relay connections is correct. Power to pin 86 flows through the electromagnet coil of the relay to ground via pin 85, When that current flows (switch is on), the relay activates and allows power from pin 30 to flow through pin 87 to whatever device you have connected - in this case the ECM.
My question is why would you use a relay in this situation. The ECM draws less than 15 amps of power (the factory configuration has it on a 15 amp fuse) and both your switch and wiring (looks like 16 gauge or larger) will handle that much current easily. Adding a relay just creates another possible point of failure in the circuit.
There are three common uses for relays... to control a high current circuit with a low current trigger, to control a constant (unswitched) current source with an ignition switched trigger, or to reverse polarity of a circuit. Yours could only fall into the first category except that the ECM is not a high current circuit. There's nothing wrong with simply running your switch output directly to the ECM - it achieves the same result without an extra component that could fail.
I’m not sure why my previous post isn’t populating. It said something about moderator approval. How long does this take? I thought it was a good ride up and I attached three pictures.
From: Jacksonville, FL (originally from Toronto Canada)
Originally Posted by tacoraptor
I’m not sure why my previous post isn’t populating. It said something about moderator approval. How long does this take? I thought it was a good ride up and I attached three pictures.
Sorry about that. Normally the forum marks a new thread as needing moderation (moderator approval). This is the first time I've seen an individual post needing moderation. I have copied the photos to the original post that started the thread and deleted the second post which had pics but no text (I think that's what caused it to require moderation).
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Electrical Wizardry HELP NEEDED 
