Howdy all. Getting ready to wire my DeWitts dual fan set up. Looking to see if anyone has an pointers or advice before i get into it. I have the diagram, just looking for what anyone has used for wire gauge, tips, or whatnot. Hoping to streamline the process and learn from those that have done it already.

 

There's a couple ways of doing it. How are you controlling the fans? Thermoswitch? Running them off a ECU? or a fan controller? Twin 30 amp relays? Or one large 60amp relay?
I pull power right off the battery cable stud on the solenoid, running a 60 amp fuse strapped to the battery cable just a couple inches from the stud. 8 guage wire to the relay, (I'm running a single 60 amp relay). 8 guage wire to the fans as well as the grounds. Mine both run together and I'm running them off my ECU. (Aftermarket EFI). I used to control them off a thermoswitch in the intake manifold and that worked fine as well.

 

Dakota Digital PAC-2800BT is the best fan controller you’ll find. Takes all the guesswork out of it and has every feature you could want.

 

Cooper Bussmann makes some nice heavy duty resettable circuit breakers. I use them for my fan and fuel pump circuits.

 

I'd planned on using the dual 30 amps that come with the kit. The car isn't in front of me, so I can't go look at the supplied wiring to see what gauge it is or it's long enough to run all the way back to the battery box (or to the starter lead as I've seen mentioned). I'll have to check that out.
Beyond that, I didnt think I'd have much need for a controller. I was going to use the sending unit in the radiator but the more I think about it, the more I like the idea of using a sender on the block. Seems a more accurate way to kick the fans on and off.
Is anyone using any ignition feed other than the "IGN" in the fusebox? I'd read some older posts about using the "ACC" feed and that makes sense to me as well, to not put an immediate draw on the battery at start.
I kinda feel I'm overthinking this but I know there's a hundred different ways to get these wired in and I like the idea of more information to choose from, than not enough.

 

I used a BMW dual temp sensor to control fans. 185/195.Pulled power directly from starter to 2 50 amp marine fuses to dual 30A relays

 

I’m in the prep stages of this as well. I recently scored a used be cool 75007 which i believe is the same spal fans in your kit.

I recently picked up two relays with pigtails, but the power in and power out, I’m going to swap to 10 gauge wire. I’ve also grabbed two 30 amp circuit breakers.

I haven’t decided on the what thermostatic switch yet, but looking at alot of the reviews on summit makes it difficult to choose, as some of the reviews are very bad. Some of the total kits seem overpriced for the parts involved and some of the kits get bad bad reviews for the quality of breakers and thermostatic switch temps being incorrect. Although, since yours is the DeWitts kit, you have all that stuff already.

So anyway, in my random daydreaming I came up with an idea that you may like and I’m probably going to work around it... I want to take 10 gauge wire off of the starter and make a lug on the firewall to run as a starting point for two wires to lead power in two respective circuit breakers and relays.

In addition to this, I want to run another wire from the solenoid and make a lug, so that I can connect a remote bump start switch for valve adjustment/compression tests etc. I suppose a remote ford solenoid could also fill the same function altogether.

 

I use a cole hersee 24059 constant duty relay/solenoid for my fan circuit and one for my fuel pump circuit. Watch out for chinese 24059 copies. 24059 made in mexico now. Have used them for 20 years and never a failure.

 

I have a 100A fuse on the alternator feeding a BlueSea fuse block. Two 30A lines from that feed two Bosch relays that feed the two Spal fans. A 195/185 switch next to the water neck provides the ground for both relay coils, so both fans come in together now, but it would be easy to change that. I have no AC, so there's plenty of room on the heater duct in the engine compartment for relays and such.

I've tested the Spal fans, and they take about 12A running. My new 3-wire Power Master amp handles it fine.

 

The ignition vs accessory-

The ignition is on during start as well- off in ACC

The accessory in on during accessory & ignition but not start.

So -you wire it to the ignition- is a hot start situation the fans could turn on while you are trying to start a hot car- not a great idea.

The acc- is off while you are trying to start the car BUT- you could accidentally turn the key back to the acc position- walk away and have the fans come on- again not a great idea.

here's a simple solution-



I'm running a PWM controller- it soft starts the fans (dual spals from Dewitts)- so at idle it doesn't use full start up current to get the fans going. But slowly (few seconds) brings the fans to speed.

And using varying voltage ( ok that's a simplification) controls the fans speed as needed - doesn't just turn them off and on.

And has an over-ride switch if needed

Derale PWM 16795

Jegs and Summit sell them






https://www.jegs.com/i/Derale/259/16795/10002/-1

https://www.summitracing.com/parts/der-16795

 

I installed the Dewitt unit on my 71 LS5. I used the wiring included with the unit and originally used the temp sensor installed in the radiator for fan control. If you do that you will have both fans coming on and going off at the same time. When I installed a Pro Flo 4 EFI on it I changed the fan switching to the Pro Flo 4 so I can change the individual fan setpoints. If you are going to use one sensor to control both fans, I don't see an issue with the sensor in the radiator. Your thermostat should be open if temp gets high enough and that hot water is going right to where the sensor in the radiator is mounted. In my setup, I wired the two red 10 gauge wires from the alternator output to the relays mounted on the front of the fender inner skirt. I tapped into the feed to the distributor for the ignition source. That is a very small current load as relay switching power, so it does not cause any issues with your ignition. The 30 amp fuses in the red 10 gauge feeds to the relays will protect your alternator if a fan has a electrical fault and I like not going through a bunch of the cars original wiring to minimize possible issues. There are plenty of different ways to wire this up. You just need to figure out what works best for your situation. Just make sure you ground the radiator to a good ground point and use DI water if you are using concentrated anti-freeze to minimize potential for electrolysis.

 

Are you or have you upgraded your alternator? Just finished my fan install/charging system upgrade yesterday; a dewitt combo with a powermaster 150 amp alternator. I have a 73. I mounted the relays on the bumper? bracket next to the driver side headlight. It had a hole available and I am adverse to drilling any new holes. I upgraded the wiring from the alternator to the horn relay and from the horn relay to the starter with 8 gage wire that had cross-linked polyethylene insulation. My wiring harness is new and I ran the 8 gage wire in parallel with the existing 10 gage wire. With the 8 gage wire, my gage will be off by a factor of 2.5 (I.e. when it reads 60 it will actually be 150 amps). I went with the cross-linked polyethylene insulation because of its higher amp capacity and its higher temperature rating. JEGs sells the wire.

Like DD smith, I spliced the fan wires to the cable between the alternator and the horn relay. I added an additional ground from the alternator to the block and I connected the fan grounds to that wire. I used external tooth washers between the alternator, block, and all other ground connections. I crimped and soldered most connections and I put all the wires in generic corrugated wire loom.

Edit: I also added a 100 amp bussman fuse and the starter.

 

The beauty of electric fans is there is a boat load of ways to control them. I prefer to keep things as simple as possible and not over think this option. DeWitts supplies the on/off switch in the radiator and both fans come on together automatically. I like this the most because it works well and it's really easy to trouble shoot when it doesn't. If the fans ever stop working, you can simply remove the wire from the switch and touch it to a good ground. If the fans come on, then it's a bad switch. If it doesn't, then it's a blow fuse or a bad relay. Fancy PWM controller and such are much harder to figure out. In addition, if you want some manual control of the fans you can simply run the switch wire into the dash and have a toggle switch to manual turn them on. Real simple.

 

The suggestion of using the DeRale PWM Electronic Fan controller (Part 16795) is a very sound one. I have a BeCool Radiator with the dual Spal fan shroud and I have been using the DeRale controller for a while and I love this thing.
You decide the temperature range of your cooling system. The sensor for the DeRale is mounted at the radiator OUTPUT and attaches on the body of the radiator.

When you start up my C3's 427 there are no fans running until it gets close to the point you set. Then the fans start at 60% power and ramp up slowly.. Once it hits the setting you have chosen it will run at 100% until the temperature starts to drop and the fan will slow down automatically to compensate instead of running wide open like many system. It is amazing to listen to the cooling fans slowing down once they get a handle on the amount of heat the engine is making.

I have a Holley Sniper Stealth 4150 and it can control the fans as well but starting them at 100% is a bit noisy. This Derale system does not need to interconnect with other systems. And just in case I have a simple Bypass if the DeRale stops working for some reason.

Thanks for your valuable Input Tom DeWitt! You are correct about keeping it simple!
My biggest issue is why have Both fans run at 100% from the very start? The 2 11" SPAL fans make a lot of noise while they move a lot of air. I use the AC switch as my manual bypass to activate the fans on the PWM controller. I also have a simple way of activating the fans manually in less than 5 minutes under the hood. I am not sure if I trust the DeRale system enough to remove my backup fan power system.

By having the Fan cooling system separate from the EFI my fans can run for a few minutes after shutdown which helps. I installed a larger Deep Cycle battery for the extra fan running time not interfering with being able to start the engine. I am hoping to be able to replace the Junk BeCool Radiator with one from DeWitts as my engine makes way more heat than a regular engine because of the high compression I am running (12.25-1) in my cast iron headed 427.

 

I like @Tom DeWitt's K.I.S.S. wiring, certainly at the start. I can make it more complicated with PWM controllers later, if I need it or just for fun, but right now the fans Only run when I am stopped.

Both fans on full are loud, but not louder than side pipes, even at idle.

 

I think this is the route I'll take to get the car running and on the road. I only just got it running on its own last week. Got the fuel delivery sorted out. Now i gotta keep it cool, get it tuned in and see i can move it on its own power for the first time.
I will fine tune it later as needed.