Here is my electric fan setup that I promised some to give the details of.

$91 electric fan from 2001 crown vic police package (ebay)
$10 2 35 amp universal relays
$20 Thermostatic switch
$ 3 Toggle switch
$ 2 Indicator light
$ 3 40 amp fuse
$12 20' 10 ga wire, 40' 16 ga wire
$ 6 universal through-the-core electric fan mounts
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$147 = an inexpensive and very effective electric fan

I figured if the fan could cool police cars racing around and then idling all day, it would have to keep my truck cool. It works so well in fact that the high speed is mainly for back up, and runs only off the toggle switch.

I had to trim 3/4" off of the fan shroud for clearance, along with the mounting bosses. I cut it with a jig saw and marked the 3/4" on the radiator side by applying 3/4" masking tape to it all the way around. It wasnt hard to trim at all.

I mounted the fan on the top with 2 peices of 3/4 x 3/4 angle and self tapping screws. I mounted the bottom with universal through-the-core electric fan mounts for ease of installation.

 

I mounted a 2 position in dash toggle switch to run the fan. The low speed enables thermostatic controled switch to run the fan via a relay. The high speed is not thermostatically controlled because I have not needed it as of yet, but it makes me feel good that I can flip it on at the bump of a switch. The dash indicator light is spliced into the high side, but comes on when either speed is on, I assume because the windings are close together in the fan. I had it spliced on both to start with, but was popping the fuse trying to start both fan windings.

I mounted the relays and thermostatic switch to the radiator overflow bracket, leaving only 3 wires to disconnect the fan to remove the radiator. I included a pic before I finished tubing and taping the wires. I think I made the wiring diagram to color match the actual wires.

 

Here is my indicator light along with my mechanical temp gage.

 

Nice setup, I am going to use dual Derale 14" fan blades / motors, in a custom shroud, with dual 45A controllers. It will be setup so that when the A/C is on, 1 fan will always come on, and if 1 fan happens to quit working, the other fan will go into a continuous loop.

 

Ya I liked the idea of 2 fans. I had 2 14" Haydens, but they wouldn't keep the beast cool. They took up less space because they were thinner, but I didnt want to invest a fortune into more expensive fans. They were supposed to move 2700 cfm's combined. If they did, I'd guess this thing moves 3700 on low and 4500 on high. Just a guess though, but they move hella more than them whimpy little haydens. I've yet to wire in an a/c switch because I haven't charged it yet since the engine swap.

I've heard good things about Derale fans. Looks like you've got a nice setup planned.

 

Because electric fans are pointless at speeds above 45 mph, Ford uses the VSS to shut off their electric fans at that speed. I want to know how to incorporate this into a system installed into a vehicle with a VSS, but without an electric fan, like my truck. I would like to be able to install electric fans, but have that feature. Any thoughts?

 

Mine shuts off when I hit about that speed anyways. Since it is controled by a temp probe in the radiator, it will automatically shut off whenever the temperature of the radiator is cool enough to cool the water. This will actually happen at the perfect speed depending on ambiant air temperature, rather than a pre set average speed. At least thats my theory, all i know is that it shuts off when I get moving.

Ive heard of temp switches that read the actual water temp, that might be where you would need the speed shut off. Reading the actual water temp sounds like a good idea, but I wonder if it would actually be less accurate. I'm not sure where you could read it right out of the radiator, as most of the plugs are in or near the block. Reading the temperature of hot water seems less accurate, as it will almost always be hot. How does Ford control the fan?

I think the radiator temp probe works well. The heat transfer is between the radiator and the water, so reading the radiator temp seems logical. If the radiator is cool due to ambiant air temp or air passing through it while driving, there is no reason to have the fan on, and the temp probe will determine that. In an extreme case, if the A/C coil was clogged with bugs, not allowing air to pass through the radiator, the temp probe would still kick the fan on if it is not overidden by a speed shut off.

I would encourage you to get a fan setup installed first, I think you would find the speed shut off is unecessary.

 

A 2 speed fan, the ECM, ECT, VSS, and three relays, is pretty much the whole system. Works something like this:

When the ECT reaches 221 degrees, the ECM powers up the low speed relay, and the fan comes on low until the temp drops to 200. The high speed relay is only activated when the low speed relay has power, and the a/c relay is then powered up. Just the a/c alone won't turn it on, unless the low speed fan is already on. The boys at Ford felt that the temp of the engine was more important than the temp of the radiator, so they use the ECT signal to determine the temp. When the VSS determines that the vehicle is driving at 45 mph, the ECM cuts the power to the CCRM (Constant Control Relay Module), which is where the previously mentioned relays are.

Take care,
~Chris

 

Thanks, I always wondered how they control it. Does the high speed come on at a high water temp also or only with the a/c? I would assume it comes on with excess water temp.

I've yet to see a good way to wire the a/c in. I think ideally the fan would come on if the a/c is running and the vehicle is traveling less than 45mph. Sounds like the way Ford has it, the engine must be warm enough for it to come on, and as soon as the water temp is cooled, the fan will shut off.

Here is what I might try when I charge my a/c:

Wire in a second temperature controlled relay on the a/c coil to run parallel with my low speed radiator temp relay. If both radiator and a/c coil is cool (ie from hwy travel) the fan would remain off, if either are warm, the low speed would turn on. The a/c coil temp probe could enable a second radiator temp probe wired to the high speed of the fan. This would enable the high speed to come on only when the a/c is on and a set radiator temp is reached. Like I said, I've not had any problems with the low speed keeping my engine cool, so the high speed would likely only be necessary to keep the engine and a/c cool. It will probably take a bit of adjusting to get it to shut off and on properly, but the fan should shut off when the vehicle is traveling fast enough to provide ample air flow.

I'm not sure how you could use the VSS to shut off your fan. Sounds like you would need a computer with fan control to run it.
Time for a 302/351 swap running a 94-95 Mustang computer.
The only thing I can think of is to wire in a second computer w/ fan control, which would only operate the fan. You would probably have to run at least 10 pins to get the computer to even work. Sounds like a challenge as you would have to splice your existing harness.

BTW, I forgot to mention that PKRWUD gave me some good suggestions on wiring my fan, and deserves credit for that. Thanks.

 

The high speed relay receives a power signal from the low speed relay, and is grounded by the a/c relay when it's active. Think of it like a nuclear missle launch switch, you know, where it takes two guys switching at the same time to make it launch. Same thing, with one exception. If the ECT becomes disconnected, the ECM overrides the whole works, and turns on the high speed fan with the ignition switch. It's like a safety. The ECM only knows that it's not getting a response from the ECT, so for all it knows, it may be maxxed out, so it turns the high fan on.

Keep in mind that the low speed fan doesn't even turn on until the ECT reads 221 degrees. Figure if they had a higher setting for the high speed fan, it would logically be 20-25 degrees hotter, which puts the engine temp close to 250 degrees. Rather than kick on a second fan, it will trigger the MIL, and encourage the driver to pull over and shut the engine off. The fan will stay on even if the key is turned off.

The VSS kills all power to the fan relays at 45 mph because it was determined that the fan powered up could actually hinder airflow at that speed. Something about the fan spinning with the natural flow of air being better. Honestly, it's been my experience that any speed over 25 mph is sufficient to cool damn near any engine with no fan at all.

I have had several customers, though, that freak out when they discover how hot the engine gets by design (afterall, they know more than the engineers at Ford, right?), so I have come up with a method of splicing in a driver controlled switch that will turn on the high speed fan at any time, yet doesn't effect the low speed fan, or it's method of operation, at all. In fact, low and high speed fan function will remain unchanged, except for the driver having the ability to turn the high speed fan on when it otherwise wouldn't be. If you end up with a '94 or newer Ford with a 2 speed electric fan (ie: Mustang), let me know, and I'll gladly share it with you.

Take care,
~Chris

 

Good info.

 

I have an electric fan controller that cuts off the fan based on speed. I just haven't had the time to install it yet. I hope to get it in the truck within the next couple of weeks. I will share results then.

My current controller uses the signal from the ECT sensor. I have it set around 205 degrees and have always been surprised at how long the truck will have to sit at idle before the fan kicks on.


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