Electric cooling fan wiring questions

[Bob Hollinshead]

There's some really nice electric fans on a lot of the late model vehicles these days. I've been told they are brushless and computer controlled. Is there any way to make them work in an older car with some basic wiring? Most of the ones I've seen have three wires-two are large like 10 gauge or larger and then a small green. How do these work?

[dannobee]

They use pulse width modulation through the engine's computer to vary the fan speed. The ecm grounds the green wire and that turns on the fan. 90% of the time to ground and you get full fan speed. It shouldn't be too hard to hook up something to make one work in an older car. And even easier if it has an aftermarket ecm/ecu.

[NewbVetteGuy]

Most of the usual radiator and fan companies have stand alone PWM controllers from $75 - $200.

Probably the easiest way to equip an old car with a brushless fan and controller. Derale has a pretty simple controller that's like $180; Dakota Digital has one for $140 that you can monitor and control over bluetooth via mobile app if you want / like a higher-tech approach.

I looked into controlling a brushless Spal fan with my Holley HP EFI system and Spal states that their fans require a minimum switching frequency of 4khz; the Holley EFI doesn't support any where near that high, so EFI system /ECU direct control can be tricky and the devil seems to be in the details on compatibility.


Adam

[Bob Hollinshead]

They use pulse width modulation through the engine's computer to vary the fan speed. The ecm grounds the green wire and that turns on the fan. 90% of the time to ground and you get full fan speed. It shouldn't be too hard to hook up something to make one work in an older car. And even easier if it has an aftermarket ecm/ecu.

So that little green wire gets switched on and off to ground at a rate needed to manage the speed the management system wants? I work in a collision shop and see these fans hitting the dumpster regularly, many of them have very light damage and some of them out of SUV's and trucks are very large. My plan is to make one work in my Bigblock 69 Nova with a custom shroud. Seems like a better way to go than the old style electric fans.

[Bob Hollinshead]

Most of the usual radiator and fan companies have stand alone PWM controllers from $75 - $200.

Probably the easiest way to equip an old car with a brushless fan and controller. Derale has a pretty simple controller that's like $180; Dakota Digital has one for $140 that you can monitor and control over bluetooth via mobile app if you want / like a higher-tech approach.

I looked into controlling a brushless Spal fan with my Holley HP EFI system and Spal states that their fans require a minimum switching frequency of 4khz; the Holley EFI doesn't support any where near that high, so EFI system /ECU direct control can be tricky and the devil seems to be in the details on compatibility.


Adam

Thanks for the info Adam I'll look into the controllers.

[Geoff2]

I tried to use a large Mercedes fan as stand alone. Had a few wires coming out of it. I got very high speed out of the fan [ & very noisy ] but could not control the speed. No doubt needed a controller to work properly. Finished up in the 'too hard basket', which was a rubbish bin....

[Bob Hollinshead]

I tested one by hooking up the large gauge wires to a battery and putting the green small wire to ground and got nothing. You can hear a click when the large wires are connected but no spin. I'll have to call some of the controller manufacturers I guess and see if their products will work with my application.

[NewbVetteGuy]

Most of the usual radiator and fan companies have stand alone PWM controllers from $75 - $200.

Probably the easiest way to equip an old car with a brushless fan and controller. Derale has a pretty simple controller that's like $180; Dakota Digital has one for $140 that you can monitor and control over bluetooth via mobile app if you want / like a higher-tech approach.

I looked into controlling a brushless Spal fan with my Holley HP EFI system and Spal states that their fans require a minimum switching frequency of 4khz; the Holley EFI doesn't support any where near that high, so EFI system /ECU direct control can be tricky and the devil seems to be in the details on compatibility.


Adam

Thanks for the info Adam I'll look into the controllers.

Last thing on this, Bob: There are some threads on the Holley EFI forums where some guys were using a fan control module from I want to say a C5 Corvette that DID support the switching speed requirements of the Spal PWM fans. (If I remember correctly, they were having the Holley control the C5 Corvette fan module, which controlled the fans.) -So it seems some folks have found ways to just go to a pick-and-pull and use an OEM fan controller to cheaply control a PWM fan. (Is it worth $100 to try and hack an OEM controller into working?)


Adam

[JCR]

Do your research. Some of the controllers mentioned do not have a good rep.

Try this guy.
https://www.autocoolguy.com/

[dennisg]

It is quite easy:
1. Buy a temperature sensing switch that conducts at your limit temperature.
2. Make a fitting to put the end of the temperature switch into the top radiator hose coolant.
3. connect the switch in series between ground and the ground side of a headlight relay, the other connections are to switched 12 volt power and the fan.
4. The fan has two wires one to the relay for power and the other to ground.

Keep it simple, use a fan that has no more than two wires. That is all you need. More wiring is unnecessary refinement just to reduce noise and save electricity.

I paid:
$5 for a swapmeet fan
$4 for the relay
$8 for the temperature switch
$ nothing for the fitting

[Bill Chase]

It is quite easy:
1. Buy a temperature sensing switch that conducts at your limit temperature.
2. Make a fitting to put the end of the temperature switch into the top radiator hose coolant.
3. connect the switch in series between ground and the ground side of a headlight relay, the other connections are to switched 12 volt power and the fan.
4. The fan has two wires one to the relay for power and the other to ground.

Keep it simple, use a fan that has no more than two wires. That is all you need. More wiring is unnecessary refinement just to reduce noise and save electricity.

I paid:
$5 for a swapmeet fan
$4 for the relay
$8 for the temperature switch
$ nothing for the fitting

The trouble with this is load on the electrical system. Fans are a huge load when. They turn on, most of the time if it can be ran with less current things can be kept smaller, lighter. And the vehicle will be more efficient to operate. The oems didn't spend the time and money going to pwm fan controllers with unnecessary complication in mind, they did it to make things lighter, more efficient. And as the op so rightly pointed out, many of these fans/control modules can be had for beer money at your local u pull yard.

[Bill Chase]

C5 Corvette pwm fan controller is cheap enough, available everywhere. Many on the mega squirt boards have mentioned success with 90's to 05 or thereabouts Plymouth grand caravan, and their dodge counterparts fan and pwm modules. 2003- and up gm trucks have some excellent dual fans with shroud that can be easily fit to many muscle car radiators without much trimming. 90-96 Corvette and or 93-2002 fbody are also a good source for good high efficiency fans that are light weight. Many of the modern brushless OEM fans can be ran with a pwm module even if they weren't factory equipped with pwm control. Spend an hour walking your local lkq and see what they have. Last one I purchased for my test run stand 3 pass radiator, dual fans with shroud and it cost me $50.00. think I got it from a grand Prix or Bonneville, do not recall exactly but the car was a series II 3800 gm supercharged. Figured it would be enough for an na small block and has worked fine. Clipped a relay socket and few feet of wire with relay out of a different car for an additional $5.00

[rgalajda]

"The trouble with this is load on the electrical system. Fans are a huge load "

Relays can help, Read this--------http://www.madelectrical.com/newstuff/


May I ask why you are contemplating converting to electric fans ?

[BOOT]

Prob can find a new connector if needed on ebay like I did for the Ford Taurus fan in my 85 TA https://www.ebay.com/itm/174776493246?h ... BM2L7A-KBg

[Bob Hollinshead]

"The trouble with this is load on the electrical system. Fans are a huge load "

Relays can help, Read this--------http://www.madelectrical.com/newstuff/


May I ask why you are contemplating converting to electric fans ?

The electric fan is the way to go or every car made today wouldn't have them. It won't usually be on a higher speeds but will be on when needed at low speeds.