This is a discussion on How to wire up dual 2 speed electric fans? within the Performance forums, part of the General Discussion category; I have a set of 2 dual speed electric fans coming in and am tryign to figure out how to ...
I have a set of 2 dual speed electric fans coming in and am tryign to figure out how to wire them up. I am not interested in a single fan or dual single speed fans. I already bought these fans from a nissan altima and need to know how to wire them up so I get all the features I want.
1- 3 position toggle switch wired up so it can turn the fans on lo, hi, or thermostat controlled
2- (2) lights wired up so 1 shows up for low and one for high.
3- Both turn on high when A/C turns on
4- Both turn on low when thermostat kicks on.
This is the closest I've found. It is for a single dual fan PCM controlled. I can modify it for a block temp switch where the low speed control is and the A/C switch for high speed.
I guess I could just use this and wire the fans in series?
Also, What are the diodes for?
Would I need resistors if I just used light bulbs and not LED's?
since you're not planning on running the fans individually (i.e. you're not ever going to try to run different speeds on different fans simultaneously, its always, both off, both on low, or both on high.) then my diagram slightly altered would work swimmingly.
1- for the 3 position switch, you'd just want to tap the high control ground to one side of the switch like in the diagram (wired at the switch according to whatever switch you get), and do the same thing for the other side of the switch with the low control ground, this would give you something like - ON(low)-OFF-ON(high), of course the actual switch that you end up using will dictate how it is wired up, and should come with the switch's schematic. I only wired up a single high speed override since it is all PCM controlled, if there was a fault in the PCM control, I don't see why I'd ever want to command low only. but thats just my preference.
2-you can wire up 2 lights just like is shown with the LED's, though its hard to say if you'd need a resistor or not, it kinda depends on the specs of the light you plan on using. I'd suggest using LED's though, they're cheap, effective, long lasting, easy to setup, and small. I actually changed my setup since drawing that diagram, I run a single 2 color LED which is really nice, it burns green when low is on, and red when high is on. works and looks great too. if you're concerned about how to wire the LED with resistors, I can help you with that, its a cakewalk if you are able to solder.
3&4 - if you're planning on using the thermostat for LOW only, then you would replace the PCM control on the low side with a thermostat which completes the ground when the proper temp is reached. and if you just want the AC to control the HIGH side, you'd need to tap into the AC control circuit to complete the high side ground loop when the AC is on. I dont use a fhan thermostat, nor have I tapped into my AC wiring, so I've never looked into those, you may need someone else to help out on them, or if you have the schematic of the fan thermostat you plan on using. I completely run mine with my PCM which is great since I can command both high or low speed on or off, based off of variables like ECT, A/C pressure, speed, etc, etc, through my tune.
so you're basically correct about modifying the thermostat and AC in place of the PCM controlls, HOWEVER, you do not want to wire the fans in series, you want to run them in parallel.
the diodes are there for relay longevity, they're entirely optional, basically, when the fan isn't running, but you're driving, the air hitting the fan will spin it and the fan motor will basically become a small generator which can (and will) send a charge up the wiring, which can adversely affect the terminals inside the relay. they're called 'freewheeling diodes' and allow a one-way path for that charge to discharge to the battery before it ever gets back to the relays (any LED's, my diagram isn't quite correct because the LED's should connect to the power signal BEFORE the diodes, if they are used...since the Mark VIII fan is quite hefty fan, that is typically where you will find them in use, I've never seen them used with other fans, so you can use them, but you may not need to. (FYI when I ran without the diodes to begin with, the freewheeling charge would light up my LED (both colors simultaneously) at my dash, after installing the diodes, I still got SOME charge lighting the LED's up but it was significantly reduced. I ended up using a relay to activate my LED to eliminate this issue.)
I modified your wiring diagram so that both fans come on low speed with the T-stat and then both come on low speed with the A/C. This way, if the T-stat is switched on and the A/C then comes on, the fans will go on high until the engine temp comes back down below the T-stat range. At least that's what I meant to do. Will the way I have this wiring diagram work?
I really like the idea of a dual color LED but never worked with them before. Where do I get them? What size resistor do I need? How expensive are they?
Diodes: Do I need them if I run a dual color LED? how would I wire them in?
Any issues with turning both fans on high with the switch? Would that make the headlights dim, etc? 1 of my fans on high seems to draw about 8-9A so I'm assuming both fans loaded would run about 20A.
Last edited by maxpower_454; 02-18-2010 at 06:58 AM.
diagram looks pretty good, EXCEPT do NOT splice the high/low wires together by the override switch (the brown and purple ones), they should be completely separate. I don't know if you meant to do that or not.
LED's are simple, normal LED's have 2 prongs comming off them the anode (+), and the cathode (-), dual color ones are just the same, and look identical to single color LED's except they have 3 prongs, 2 separate anodes (one for each color), and a common cathode.
I just got home from school and have been up for ~20 hours, I'm wrecked and have to go to work in about 3 hours. so I'll post up some good info for you when I get to work tonight, but I gotta go get a little rest.
I got a flexalite controller and fans. Able to make it high low or nothing at all. simple on offs no 3 way toggles
Nice diagram by the way! What controller are u using?
I want a 3 way toggle. That's why I have one, not because I need it. I want to be able to turn then on high or low and don't want more than 1 switch.
I'm thinking of using this adjustable one. It's cheap and adjustable:
or else this preset in block T-stat. But it's almost as expensive as the adjustable one so I'm leaning toward the adj one:
I remember working with diodes and LEDs a little in school. I plan on using this LED:http://www.parts-express.com/pe/show...TOKEN=33587499
Using Ohm's law, I calculated the resistor needed as (12-2.2)/0.04 = 245ohm for the brightest setting. Sound good??
Updated diagram. I still have to figure out how to make both go on high with the other switch setting though:
Last edited by maxpower_454; 02-17-2010 at 07:38 PM.
Ok lets start with ur switch, im not fam, with the 3 way toggle whats the prongs on the back, im familair with a 2 way led
note fsc's clock is off!
so why does diagram 1 have a controller and diagram 2 doesnt have one?
and why do u have 2.... 2 speed fans? ur running 4?
If u didnt have 2 sets of 2 speed fans you wouldnt have both sets of positive and negative in the diagram
think u just got an extra dual fan on ur diagram some how
you got ohms law right, but remember that when the truck is running, you're not at 12V, more like 14.5ish. so I would get something like a 1W or greater 470 ohm resistor (yellow violet brown code)
that looks like a decent LED, I like this site for electronic parts better, you get alot more information from them on the pieces, here's a good Red/green LED (they have some other cool color combos you can find too so if you want to match to a color scheme or something, but if you get a different LED you may need a different resistor vale for it)
and here's a good 470 ohm resistor, you'll need one for each anode on the LED, they're cheap though, I'd buy a few to have some backups just incase.
then you'll want something like this to mount it:
they've also got any swtiches you'd ever want, and anything else.
I'm not sure I understand what you mean by: "I still have to figure out how to make both go on high with the other switch setting though"
The dual two speed fans run just like you have already figured out, both coils need to be in parallel for high speed and either coil will run it on low speed. On my Van the 7730 controlled both fans independently and the 7427 runs both as high speed only.
1997 G1500, 5.7, 906s 2.02/1.60, GM 395' marine cam, 1.7 RR's, Marine Intake, BBK TB, 85mm MAF, 6.5 aircleaner, Thorley Tri-Ys, Thunderbolt 2.5 cats, Dynomax 22865 muffler, 4L80E, 0411, Hydroboost, 9.5" 14-bolt 3.73s, 8800 GVW front calipers, March 4490 pulleys, AD244 alt, D-Max fan
If you're going to run two dual speed fans off of one relay (for either High or low, but especially the high setting), there's going to be a pretty high initial draw at startup. Make sure you use a fairly high amp rated relay.
Use a relay of too low an amperage and it'll most likely weld itself into the "on" position.
I run a single taurus dual speed fan and use a cole hersee constant duty 24117 85A relay (PVC coated since it's under hood) just for safeties sake.
I believe that this:
Is more of the setup you're looking for....
Last edited by gr8twhite; 02-18-2010 at 05:48 AM.
Detroit 6.5L Turbo Diesel400,000 kms and still rattling.....
I see you just got rid of the connection between the purple and brown wires. That will make it so both fans are on low in both positions on the 3 way switch. The way I had it would make them both go on high in either switch position. I guess I can ditch the idea of having the 3way toggle. I don't see why I would need to have both go on hig from a switch anyway. Low should be fine. With it wired up this way the manual switch would turn on the A/C side fans and if the engine was still hot the thermostat will still work and turn on the other side which would turn both sides on hi.
Also this way I can just go with a light up switch althought I'd really like to have a dash light showing the fans on. I guess I can still do that also.
Last edited by maxpower_454; 02-18-2010 at 07:23 AM.
Here's more what i had in mind with you four pole switch idea :
But look at it closely, I haven't had much sleep since Saturday (about 10 hours, couple hours at a time) and am getting a little "punchy"........
Last edited by gr8twhite; 02-18-2010 at 07:57 AM.
Detroit 6.5L Turbo Diesel400,000 kms and still rattling.....