The PCV will have a pretty constant power draw, lets say 1A@12v, I would probably put a 2A (or 1.5A) fuse to protect that component as if the PCV is drawing 3A there's probably a problem and I want to try and protect that circuit by cutting power to it.
My fuse rating estimate is close to yours. I was thinking no bigger than 3 amps. The DJ tech told me AutoTune does not need an inline fuse but a 5 amp should be fine if I am making a dedicated circuit for it. Installation instructions for Autotune say the tail light is a good source for power so a circuit with lower amperage is probably better than a high one. The PC5 and ignition module are powered off of the connection to the main wiring harness at the throttle bodies so there is no guesswork there. Plug it in and don't worry about a fuse. I'm less concerned about the power for the DJ modules since they seem to be designed to be fairly plug and play when it comes to the electrical work necessary to install them. It is the switches that connect to the inputs I'm concerned about. Normally, you just run a wire from Input 1 to Input 1 (Ground). The power is already there in the module and you are just closing the circuit to ground. Some of my switches will carry extra power that never was in the module in the first place. For example, I have an LED to indicate Map 2 and another to indicate Map 1. Map 2 is the ON position so I can use the power from the switch input to light the LED as the power flows through the switch to the switch input ground. Easy. Map 1 however is the OFF position so the map switch circuit will be open. If I want an LED to indicate Map 1, I need to get the power from the city lights which I believe is on the 15 amp Headlights Low Beam circuit. If I ground the LEDs that are powered off of the city lights to the modules, there is a chance 15 amps could flow through the module and obviously I want to avoid that. I'm sure the amount of power that normally goes through those little switch inputs into the tiny circuit boards is just milliamps. I trust a few 2 milliamp LEDs will not overload the digitals grounds in the modules but better to be safe than sorry. I ordered a multimeter and I'm testing the switch input amperage and the LED amperage. If the combined amperage of the the LED(s) is more than 30% of the normal current in the switch input, I will probably just ground the LEDs to the city lights negative wire. I guess most people would choose some ground other than the switch input ground but I like the idea of at least grounding them to the module if the power is can't be drawn from them. That way, if something is wrong with the module, chances are the LEDs won't come on. Of course, I don't want to have the LEDs be the source of the problem if the module should end up getting cooked. LOL an indicator light on the switch to tell you when the switch has destroyed the module!
You are thinking about connecting a few other components to the ground circuit/wire of the PCV. This circuit is most likely NOT protected by a fuse since typically fuses are placed as close to the power source (battery) as possible
Agreed. Why would DJ put a fuse before the switch input grounds if there is already a resistor (or something similar) where the power comes into the module? They didn't design their product to have any other power come in other than what is intended to power the module.
You could connect a fuse to the ground wire, making sure that it is sized small enough to protect the wire itself however if this is a common wire to the LEDs + PCV and the fuse blows you will lose power to your engine which could be very dangerous depending on when and where that happens.
Yeah, thought of that too but if I put the fuse in the ground wire, might as well out it right at the power source which is the RH city light connector. I can have a fuse just for the LEDs--or I could have a couple fuses and split the load between two fuses--or three if I want (there will be 5 LEDs that require the outside power source).
All of the LEDs that require an outside power source are not drawing power off the module so if the fuse blows, it will not effect operation of the modules.
I personally prefer to just run a new ground wire from the frame and connect all of these LEDs to that, if you are using a common source (positive) wire, use a fuse on that wire only.
Yeah, most people would. I might end up doing that after all.
* Last updated by: Rook on 11/17/2017 @ 4:30 PM *
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