I just received delivery of my Flex-A-Lite 270 electric fan from Jeg's and am getting ready to install it. I'm wondering, is it totally necessary to wire it up with the air conditioning? Won't the fans just kick on anyway when the coolant temp gets high enough running the A/C, instead of having the fans running all the time with it on? I'm just thinking of avoiding having the fans run when at highway speeds, or in the winter when the defrost is on and the A/C kicks in. I know about the override switch that can be installed to shut the fans off manually. I live in the Chicago area and only run the A/C occasionally; I'm more of a windows-down kind of guy (like to hear that dual exhaust!) Wanted to get some opinions or tales of experience, or to hear why this idea is totally idiotic. These forums are fantastic for that! Thanks a lot, folks.

 

I can think of one reason why they want the fan on all the time when the ac is on...
If you had it where the fan wasnt on, then the head pressure on the high side of your compressor will be too high causeing accelerated wear on your airconditioner compressor. Most likely the cycling time from the engine temp would be too slow to prevent this from happening.
You could have a override switch on the fan for when you are moving fast enough as long as you are certain you wont forget to turn it back on everytime.

 

It will work. What you will find happening is that the coolant temp gets hot so fast that 1 fan cannot keep up so the second one will kick on for a brief period till the temp goesback down. I don't have the Flexalite system but I do have full manual control of both fans. I use 3 switches. One is a master off, kills all power to the fan temperature controller relays. The other two are master on. They turn on the fans individually regardless of the position of any switch or sensor. Hear is a picture of the switches mounted in the Overhead consol. I hase since added the third switch for the second fan.
https://www.f150online.com/galleries...3442-82391.jpg

Regards

Jean Marc Chartier

 

Another reason to hook up the a/c to the fans is for setting at red lights. If the fans are not on, you get no airflow through the condensor and the air coming out the vents soon will be warm.

 

I was just at the AC shop and I have a home made dual electric fan setup. I had 1 fan coming on with the AC compressor. The AC guy had his gauges hooked up and he thought the head pressure was too high then I flipped the switch turning on both fans and the head pressure dropped big time. I then wired my fans so they both come on with the AC compressor. My AC is incredibly cool now. My condensor had a crack in it and he thinks the high pressure from having only 1 fan running may have contributed to the demise of my condensor. The only problem is when both my fans cut in I get a major drop in voltage and it dims my lights and blower fan. I need to work on getting the second fan on a delay so they dont both come on together.

 

If you hook up the 270 correctly to the AC, the fans will only come on when the condenser kicks in. In other words no fans with the vent, the heater, the defroster, etc.

In the winter time in Chicago I doubt the fans will ever come on.

My experience is that in highway driving the fans seldom come on when the ambient temperature is below 65 degrees. When I get into traffic they will occasionally come on in a stop and go situration or at a stop light. The way these things work they will come on when the temperature gets too high or the AC condenser kicks in. They will initially come on at about 60% of top speed. If both conditions occur the speed will increase to 100%.

Hook up to AC condenser signal. You will be pleased.

 

Hey, thanks a lot for the great advice. Now I know the reasoning behind having the fans turn on with the A/C. I'm definitely going to do it. Sometimes I just need to know why. I'm bullheaded that way. Thanks again!

 

I live in Canada and when the fans are connected to the compressor the compressor comes on when in Defrost or floor/defrost, even in the winter, and then of course the AC modes. The fans will come on in the winter as well unless you put a switch in to stop this from happening. The compresor comes on in the winter as it is used as a dehumidifier to help keep the windshield clear. There are some guys on the web and maybe even this site that have modified thier selector switches so the AC compressor will only work in Defrost or AC modes and not the Floor/defrost mode.

 

A little tip that you can find elsewhere if you search this site - when looking for the the signal wire for the clutch compressor do not bother looking for the two wires that go the clutch compressor per the wiring instructions.

Go to the power distribution box which is under the hood on the driver's side of the engine compartment. Open the box and locate the A/C clutch relay. In the 2003 F-150 5.4L it is half relay 204. Take the box off and open the bottom. There be five wires coming out of the location for the half relay. Locate the wire that is hot only when the condenser is running. In my case it was a grey wire with white stripe.

This is where I tapped in and my system works just as advertised.

Second Tip: Go to the flex-a-lite site and download the instructions in Adobe. Much easier to read and the pictures are clearer.

Third Tip: The fan can be difficult to attach to the brackets which attach to the old supports for the fan shroud. Especially the lower screws. To get around this I loosely attached all the brackets, etc. Then I lowered the fan into the opening and attached the brackets to the old fan shroud location. Adjusted the fan and brackets to the desired location and hand tightened the top screws to snug. I then removed the entire assembly and inserted the bottom screws and tigthened them before reinserting the entire assembly.

LOL

 

Do your headlights Dim when the 2 fans cut in? Mine is home made with 2 tauras fans and the headlights dim then return to normal when I have both fans cutting in at the same time.
To install mine I just had to grind a bit off the tauras shroud and then using black tywraps attached it to the rad. The tauras shroud even has a lip that fits between the rad tank and the fins to help hold the sides in. I need to borrow a camera and show you guys this install it is slick and looks factory. Oh and costs way less than the factory units. Even the guy at the AC shop was impressed as to the install he even said he never saw a F150 with factory fans before so I had to let him in on my install.

 

Haven't notice a dimming of the lights when the fans turn on.