Good info

I have 130 amp 3g alternator so I have plenty of charging capacity.

I wonder if I can wire it up so one fan kicks on at say 185 and the second kits on at a little higher.  Guess I would need two sensors to make that happen. Maybe I'm just overthinking it.  LOL

Guess I need to figure out where to install the thermostatic switch since my intake port has temp sensor for water temp gauge and don't think my thermostat housing has a port.

I faced this challenge when wiring up a pair of big SPAL fans for my Lightning. They have a massive inrush current so you have to plan your relays and wiring accordingly. It's definitely a good idea to stagger the fans coming on. You might also want to consider turning at least one fan on automatically when you kick the AC on if you have AC. I would recommend a good controller, there's quite a few out there that make it pretty easy and are very adjustable.

If you're interested I could share my BDWD (big dumb wiring diagram), but it got out of hand pretty quick with AC control, WOT cutout, AC high side pressure cut, etc, etc.

mounting the fan relays on the shroud IMO is just messy and a bad idea

I have mine mounted close to where the regulator is and wrapped everything in blac electrical tape to match the factory wiring, and soldered wires instead of using any other connectors (except for the fan disconnect)

you can make that circuit that TKO suggested, or go with the premade ones depending on how much money you want to spend. SPAL has one thats variable speed .. I am using Derale 16759 which works very well. Variable temp, not speed.

Yes, its what I run.  It takes a bit of fiddling to get them set right, but once done they seem to be foolproof.  I haven't touched mine since I put it in a couple years ago.  Brings the fan on at 195 and shuts it off at 180 based on where I have it set. 

1fststang wrote:

I'm installing dual electric fans from a late model ford that are supposed to pull like 3500 cfm.

I'm thinking I want  to wire these up so that they come on separately to avoid a larger amp draw all at once or have both come on but on slow speed then go to high when they reach a set temp.

Any feedback from anybody on how they have wired dual electric fans ?  I may just use relays and a typical sensor to trigger or may use one of the controller boxes that offer the variable speed option.

I'm thinking also mounting the relays and or controller box right on the fan shroud?  good idea or no?

Definitely plan to have an override switch as well as switch on from my vintage air.

thanks and sorry for all the questions this week. Trying to get some stuff done.

 
What late model ford did you get the fans from?

BillyC I believe they were from a Ford Contour. 

I had researched online and a lot of people were using this fan set up with good success.  I bought it new from online supplier for not a lot.  I can look up the paperwork if you want more info on it?

The fans are supposed to pull about 3,500 cfm.
 

I've ran a DC controller for over 10 years and works really well.    http://www.dccontrol.com/Multispeed.htm

https://www.rockauto.com/en/moreinfo.php?pk=7148432&cc=1106390&jsn=480

TKOPerformance wrote:

Here, this should work.  It will take three relays, but allows each fan to be set for a different temperature, provides override for each fan, and automatic triggering of one fan when the AC compressor comes on.

 
You might want to move that lower override switch to the relay #2 ground instead of routing the 12V + relay output from that relay to ground via that switch.

Otherwise pop goes the weasel!

Edited to remove old schematic... less confusion!

Last edited by 351MooseStang (2/17/2019 6:15 AM)

I have a spal fan control tucked away some place .If you are interested in it let me know .Removed it when I went to fuel injection.

Yeah I might be interested in the Spal control

Still debating how I want to run the dual fans and need to confirm they can run 2 speeds which I believe I read they will.

After researching some I found that I can buy a temp control switch that has dual temp sensor in one unit. Low speed triggers at 180 and high at 195.

Trying to think thru if I were to use this I could easily figure out how to trigger the first fan at 180 then turn on the second at 195. That would take load off the relays and such by not having both kick on high at the same time.

What I'm trying to figure out is can I wire it up so both kick on low speed at 180 then both kick on high if it reaches 195?

I also found a Volvo 2 speed relay system that sounds like it might work well with this sensor.

Any thoughts on using these components  or experience with them?  If I use a single temp sensor to turn them both on at same time on high what kind of issues might I experience?  I am running 130 amp 3g alternator. Below is the info on the volvo relay set up.

I'm want to keep it simple as possible but very reliable.