I'm looking for a 12V keyed/switched power source for a E-fan I'm wiring up on my 2001 Ranger 2.5l I4 Lima. I'd prefer under the hood, but preliminary Googling has me cautious--says the only sources there are critical and best left alone. Is there a way to stay under the hood? The firewall is a pain...

 

You will use a RELAY rated for your e-fans amp load, like 12v 40amp relay

The coil in the relay that activates it can be added to any key on circuit without adding to its load, relay's coil are rated at .3 to .5amps, 1/2 amp at most

So you use an inline fuse, rated for e-fan load, from battery to RELAY, then from relay to E-fan controller

Battery positive--------(fuse)-----------relay(30)/////relay(87)--------------------------e-fan controller

Most of the engines RED wires are 12v key on, not engine bay wires, engine wires, easiest to use or find would be the RED wire on MAF sensor, or the RED wire on IAC Valve, these both have Key ON 12volts

You can use a wire splicer, like those used for trailer wiring, to tap one of these RED wires, then run a wire to added RELAY 85 post
Then GROUND RELAY 86 post

Automotive Relay diagram seen here: https://www.enginebasics.com/Advance...%20Picture.jpg

The numbering comes from the old volkswagons, lol, that's why they seem odd, they were the first to use this type of relay
85 and 86 are the low amp side that activates the relay, one is a ground and the other is 12volts, doesn't matter which is which, this has no polarity, relay only activates when it has BOTH a ground AND 12v
This is the voltage rating for the relay, a 12v relay will activate when it has 12volt and ground, a 5volt relay would activate when it has 5v and ground, a 110volt relay would activate when it has 110v and ground, ect...........

30 and 87, this is the high amp side, the LOAD rating for the relay, like 30amp load rating or 40amp or 100amp, this has to do with the size of the contact plates inside the relay
30 and 87 are only connected when relay is activated
87A is a new addition, you can get 4 pin relays that have no 87A, but most are 5 pin now and you just don't use 87A, but you can see how that contact could be useful

So fused power from battery goes to 30
87 is connected to e-fan controller
when key is on relay activates and connects 30 and 87 together, so e-fan controller has power, and when temp is high enough it will power up the fan

 

Ample knowledge dispensed, Ron, my man. My inquiry was based off of the directions from an E-Fan controller, which includes all I needed to get my new E-Fan up and running properly (thank you, thank you). I posted here because I didn't want to run through the firewall for 12V switched power. Like I said above, the first 2 or 3 page results said to not mess with 12 switched underneath the hood. I said "okay, I wonder what RonD has to say about that?" But I'm on a time crunch, so couldn't wait for a response. I just ran through the firewall to the radio's switched power to satisfy the directions. I actually do have a sense of relays, but this controller also can be switched on with the A/C, so I was confused a little as to what the switched wire was for. I didn't even check to see where the wires lead to on the relay (as of writing this post I still haven't checked, but will soon).
After reading your post, my guess is both the A/C clutch wire and 12V switched lead to the 85 (or 86) post. The kit is thorough--both the battery wire and the wire leading to the fan power source from the relay are fused (25 amps).

My question to you, Ron: the E-Fan controller's A/C wire is soldered in a few inches behind the truck's A/C clutch condenser harness. It has what research has lead me to believe is an anti-spiking diode. It is underneath heat shrink tubing, so I can't be sure, but something is there. I read it is safe practice to put a second anti-spiking diode between the factory clutch plug harness positive and negative wires, if one is not included from the factory. What do you know about that and would you recommend it?

Other than that, the fan is installed (no shroud yet--I'm going to read my other thread next where I believe you address that), truck test driven, and the temperature is holding steady. The temp actually decreased some 2 times during the test; my guess is that is when the fan kicked on and all other times I guess a fan is not really that necessary to maintain a safe temperature. And I did let the engine sit and idle for a minute--all is good so far.

 

The AC clutch's 12volt wire on the compressor is a common place to add e-fan activation, it would depend on the wiring the e-fan controller uses to determine why they wanted/needed to use a diode(one-way electrical valve), but doesn't hurt to have it
It would be used with the Temp Sensor, which I would assume is 12v activation as well, so either 12v from temp or AC clutch would cause fan to activate, in that case the diode would prevent AC clutch activation when Temp sensor activated e-fan
So temps 12v does flow to the clutches 12v wire, diode blocks it

No, I don't see a need to add a diode across the AC clutch's 12v and ground, its just a coil, again it doesn't hurt anything to use one

 

Well, Ron, you're a knowledgeable dude, and I'm going with what you say. Looking at the wiring diagram that came with the controller, it's not too complicated. The relay is switch is closed by the therm. or A/C, giving power to the fan.

When it comes down to it, adding a diode across the clutch harness is extra work that (I trust) isn't necessary. If I'm honest, I don't exactly see what it would do? The clutch power is run straight to the relay (85), so understanding from your post, I don't see the need for a diode. It may not be--something on that wire is under heat shrink tubing. What it is is a guess.

I love to learn, so if you feel like spelling it out for me, I'll read every letter you type. But, as far as this project, I trust that an extra diode is a hassle that would provide no benefit or safety?

 

Sure, if relay coil is wired with 86 as a ground and 85 as the 12v trigger to activate it, its all pretty simple unless you want to add TWO triggers

85-----------------temp sensor--------------12volt
...\---------------AC Clutch wire-------------12volt

If both are connected to 85 then when temp sensor sends 12volt to 85 to activate relay that 12v will travel up to the AC clutch wire and activate the AC clutch at the same time

so you do this
85--------------------------temp sensor--------------12volt
...\--------(diode)-------AC Clutch wire-------------12volt

So the 12v from temp sensor can't travel back to the AC Clutch, but 12v from AC Clutch can still activate the relay

The temp sensor doesn't care about the 12v from the AC Clutch circuit, it already has 12v on the other terminal


Just as an FYI
Most Factory relays use the ground as the trigger, not the 12v
This means less wiring and safer wiring

The few 12volt wires there are the less chance of a short, and vehicle grounds are every where, well everywhere there is METAL, lol

Say I wanted to add fog lights with a switch on the dash

I add the relay in the engine bay for the Load/lights then just put a 12v jumper wire from 30(battery power) to 86, so coil has 12v all the time
Then run one small "ground wire" from 85 into the cab to a switch, then ground the switch inside the cab, so switch ON grounds 85 and relay activates, fog lights on
Works with lighted switches as well, light turns on with switch on, because "Current" is flowing when relay gets ground
And worse case SHORT in the wire to the cab, the lights come on, lol, so no magic smoke, melted wires or fire

You will find most of the factory relays are wired this way, ground as the trigger

 

Oooh, I'm tracking now, Ron. And it is a diode (IN4005), it's right there in the wiring diagram. Haha, I don't know how I overlooked it.

Interesting about the polarity of factory relay wiring. Wish I would have known that when I wired my fogs a few months ago, may have saved me some wire runs. For the sake of clarity, if the coil is hot, how come it doesn't cause the switch to close? I thought current to the coil in relay causes magnetism to close the switch and power flows? I also heard that current in DC circuits actually flows from negative to positive, so therein may be my answer. Where there is voltage there is not necessarily current, being voltage is potential current, not a flow of electrons? I guess magnetism is not applied to the coil in relay until it has a ground? Completes circuit? I'm kinda brainstorming here (if you can't tell)...

 

Yes, the + and - flow does actually go from - to + but.............doesn't really matter for basic electric or electronics wiring

When this was first tested the instruments weren't good enough to see the actual direction, so 50/50 chance of getting it right, they didn't, lol

When it was finally proven, car makers tried POSITIVE "Ground" vehicles................people would get shocks opening the door, lol, so that didn't last too long

Think of a tube with ***** inside, if the ***** are just sitting there there is no energy released, if I tilt up one end of the tube but lower end of tube is blocked I have potential energy but still no energy released
If I unblock the lower end of tube then potential energy is changed into released energy as the ***** roll out

Electricity uses electrons as the ***** and the wire is the tube
If I apply 12volt pressure at on end of the wire but other end is not connected to anything then electrons just sit there, no flow
If I connect 12volts to BOTH ends of the wire then electrons also just sit there, same pressure at both ends no "tilt", no flow

But if I connect 0volts(ground) to one end then electrons start to flow, there is current, this current can heat up light bulbs, making them glow, or magnetize a coil of wire around a metal core, because electrons are flowing
If I disconnect either the 12v or 0volt, flow stops, no energy released

So 12volts on its own is not power, there also has to be a lower voltage to make electrons flow, or a higher voltage, 24volts will flow to 12volts, same as 12volts would flow to 0volts

That's DC direct current, + and - never changes

AC, alternating current is much the same, but think of the tube again, with the *****, if I were to tilt the tube up and down in both direction, ***** would "flow" back and forth, not from one end to the other, but they WOULD flow
AC has a + and - but it changes very fast, it "alternates", and as AC switches "polarity", 60 times a second in USA, this causes electrons to oscillate back and forth releasing energy, but if you disconnect either wire then it stops oscillating, no energy released, light switch off


Thomas Edison developed DC systems, but DC doesn't work well over distance, its also hard to generate DC directly, in any larger sense, i.e. multi-home electricity

Nikola Tesla developed AC systems, and licensed it to Westinghouse, electricity "wars" began, spoiler alert!!!.................................AC won, lol

But we do use the less efficient 110vAC in North America, most of the world uses the better 220vAC
That's because of the "wars" 110vAC sounds less dangerous the 220vAC, lol, and Edison's company always harped on their lower voltage DC system as being safer, but its the "AMPs that kill you not the Volts".

 

Great read, Ron. It really whets my appetite. I think I will pursue this further with my own research.

I have an immediate question: if current flows from neg to pos, you could say current is in the ground/metal of a car, right? Why no shocks?

 

Because YOU are a ground, not a positive, and why positive ground vehicles DID shock people when they touched the metal door handle

So you have same electrical charge as battery negative, well close to it
And the metal of a vehicle has Potential energy, not current, same as you have
If you wear wool socks and shuffle your feet on carpet you can build up a static charge in your body, potential energy, if you touch someone else or metal door **** you will get a discharge, current flows at that time

That's actually Lightening just a less powerful discharge, lol

 

Okay, cool. Well, any further questions I have will be answered by research. Thanks for sharing your knowledge.