Cooling fans- electric vs mechanical/clutch

[Jacob84]

So I actually already have a 3G alternator on the truck, it’s a standard 90amp though. Extra electrical loads I have are an electric fuel pump, efi system, and MSD 6AL ignition. Other than that it’s just standard lights and such. When I swapped in my 95 351w motor I also swapped in all of the accessories at the same time so now I have a serpentine system along with new accessories (will put that in my signature, need to update it).

I appreciate all the feedback and opinions guys. Noise isn’t a big deal to me, I don’t mind to hear something working (as long as it’s working properly, if it’s not it drives me crazy). I also highly doubt an electric fan is more efficient when it’s running full tilt compared to a mechanical one. I think where it has benefit is when you’re rolling down the highway or it’s cold enough outside to have no need for extra cooling just yet. Functioning only when needed as it was said. Plus it cleans up the engine bay in my opinion. But if all it does is make for a more complicated system with no real benefit then I’ll probably pass. I’m a younger guy and take all of y'all’s feedback seriously so keep it coming if you have any other opinions or ideas.

I’ll check that crown Vic fan out, I figure it’s probably a two speed. If so, I’d like to hook up the lower output up to a switch for my AC and have the higher output side for actual engine cooling when needed if that sounds like a decent plan

[grumpin]

I appreciate all the feedback and opinions guys. Noise isn’t a big deal to me, I don’t mind to hear something working (as long as it’s working properly, if it’s not it drives me crazy). I also highly doubt an electric fan is more efficient when it’s running full tilt compared to a mechanical one. I think where it has benefit is when you’re rolling down the highway or it’s cold enough outside to have no need for extra cooling just yet. Functioning only when needed as it was said. Plus it cleans up the engine bay in my opinion. But if all it does is make for a more complicated system with no real benefit then I’ll probably pass. I’m a younger guy and take all of y'all’s feedback seriously so keep it coming if you have any other opinions or ideas.

I’ll check that crown Vic fan out, I figure it’s probably a two speed. If so, I’d like to hook up the lower output up to a switch for my AC and have the higher output side for actual engine cooling when needed if that sounds like a decent plan

I can’t remember the situation, but I helped someone with an electric fan. Ended up taking it off because it would not cool the engine enough.

I’ve had others say they have their place. I wouldn’t put one on a daily driver.

I like that noise Bill is talking about! I know it’s up there working!

IIRC our Suburban has a fan plus an electric fan in front of the A/C condenser.

Just my opinion.

[ArdWrknTrk]

.... I also highly doubt an electric fan is more efficient when it’s running full tilt compared to a mechanical one. I think where it has benefit is when you’re rolling down the highway or it’s cold enough outside to have no need for extra cooling just yet. Functioning only when needed as it was said. Plus it cleans up the engine bay in my opinion. But if all it does is make for a more complicated system with no real benefit then I’ll probably pass. I’m a younger guy and take all of y'all’s feedback seriously so keep it coming if you have any other opinions or ideas.

I think the point you're missing is that the fan has a thermostatic clutch (in most cases)

I can easily start my engine while holding a fan blade with one finger, by jumping the relay while everything is cold.

It does develop some inertia, and I wouldn't want to stick my fingers into a spinning fan.

As the clockspring on the front is warmed up by heat coming off the radiator it slowly closes the orifice in the viscious coupling.

At highway speeds in bitter freezing weather the fan is essentially freewheeling.

Is it a parasitic load? Yes.

It is also infinitely speed adjustable, not on/off or two speeds.

It does not involve at electrons to "let the smoke out", an alternator, thermostatic switch, battery, relays, wiring, plugs, or electric motors to function.

My fan clutch has gone bad a couple of times in the 455,XXX miles I've owned this truck.

Fortunately, it didn't take out the radiator.

ETA: both times on long, hot road trips....

One time dragging the race trailer back from Daytona it locked up in rural Virginia.

Man, they do sound like an airplane!

I nursed it along a couple of exits to civilization.

There was a NAPA in sight of the ramp.

I pulled a thin pattern 11 or 12mm out of the pit box as I sent Alex inside to get a replacement.

A deep 14 loosened the the power steering, and a 1/2" drive breaker bar tightened it up.

We were out of there and on the road in 20 minutes...

Not to say you couldn't get a Taurus fan motor in bumble'bees' Virginia, and this was back in the late '90's when parts were on the shelf instead of in the warehouse.

But there was no mobile internet to guide us or call ahead either.

Sometimes I miss the days of paper maps.

[85lebaront2]

I appreciate all the feedback and opinions guys. Noise isn’t a big deal to me, I don’t mind to hear something working (as long as it’s working properly, if it’s not it drives me crazy). I also highly doubt an electric fan is more efficient when it’s running full tilt compared to a mechanical one. I think where it has benefit is when you’re rolling down the highway or it’s cold enough outside to have no need for extra cooling just yet. Functioning only when needed as it was said. Plus it cleans up the engine bay in my opinion. But if all it does is make for a more complicated system with no real benefit then I’ll probably pass. I’m a younger guy and take all of y'all’s feedback seriously so keep it coming if you have any other opinions or ideas.

I’ll check that crown Vic fan out, I figure it’s probably a two speed. If so, I’d like to hook up the lower output up to a switch for my AC and have the higher output side for actual engine cooling when needed if that sounds like a decent plan

I had actually drawn up a system for a non-computer controlled two speed electric fan on a truck, problem I ran into is there is only 5 1/2" between the water pump shaft and radiator with a 460 due to it's length.

On the electric vs mechanical fan question, a good electric fan, not one of these aftermarket ones, will move a lot of air on high speed regardless of vehicle or engine speed. When you are sitting in heavy traffic on one of our summer days when the heat and humidity race to see which is higher, in my case, engine is at 750 rpm, running the AC, fan clutch comes in and the water pump and fan might be at 900 rpm, and electric at high speed will probably move 2-3 times as much air.

On the Chevy tuck I helped a friend with, the 1996 auxiliary cooling fan on it has two control modes, one is AC pressure, the other is engine temperature. The temperature switch closes the relay, the AC pressure switch closes the relay and puts the AC system into recirculation mode to reduce part of the load on the system. I am attaching that if it will help.

The controls I had drawn up would run the fan on low whenever the AC compressor is engaged or the engine temperature exceeds 230° F (if I remember that correctly). If you use one of the older idiot light "hot" switches, it should close around 210-220° F for normal engine cooling, high speed can be done with a high pressure switch on the AC system (1994 Taurus used a binary switch, high fan enable then if the pressure was still too high, compressor shut off) this can be installed in place of the existing compressor cut off switch.

[Nothing Special]

This is something that has always not sat well with me lol. How does an electric fan save gas mileage? The laws of conservation of energy/thermodynamics would basically say that electric fans should use MORE energy than a mechanical one.

Think about it. The engine turns, turning the fan, done.

If you use an electric fan, the engine turns, to turn and alternator (energy is lost) which then charges a battery (energy is lost) which then passes through a relay/fuse system (energy lost) then finally powers the fan. So those electric fans require more power from the engine in order to run.

As already noted "they don't need to run all the time" is the stock answer to this question. And as also already noted, "but mechanical fans don't either" is the stock reply to that answer.

I just can't see electrics being a big (if any) improvement in economy, and the car companies must not either, because as I noted above, for a long time about the only cars with electric fans were the ones with transverse engines where a mechanical fan would be pointed at the right front fender instead of the radiator. If electrics were so great everything would use them. But lately it seems like everything is starting to use them, so maybe there is something there.

Bottom line for me on the economy question is that electrics MIGHT be a little better, but if they are it can't be a whole lot.

 

[85lebaront2]

This is something that has always not sat well with me lol. How does an electric fan save gas mileage? The laws of conservation of energy/thermodynamics would basically say that electric fans should use MORE energy than a mechanical one.

Think about it. The engine turns, turning the fan, done.

If you use an electric fan, the engine turns, to turn and alternator (energy is lost) which then charges a battery (energy is lost) which then passes through a relay/fuse system (energy lost) then finally powers the fan. So those electric fans require more power from the engine in order to run.

As already noted "they don't need to run all the time" is the stock answer to this question. And as also already noted, "but mechanical fans don't either" is the stock reply to that answer.

I just can't see electrics being a big (if any) improvement in economy, and the car companies must not either, because as I noted above, for a long time about the only cars with electric fans were the ones with transverse engines where a mechanical fan would be pointed at the right front fender instead of the radiator. If electrics were so great everything would use them. But lately it seems like everything is starting to use them, so maybe there is something there.

Bottom line for me on the economy question is that electrics MIGHT be a little better, but if they are it can't be a whole lot.

For a good alternator to provide the current needed to run a large fan at high speed the engine power consumption is probably substantially less than the power needed to turn a large 5 or 7 bladed fan. In order for a mechanical fan to move enough air at low rpm it has to have a high attack angle (blade angle in relation to a flat plane), this coupled with the fact that is overdriven by the crank/waterpump pulley ratio means that as the engine rpm increases the fan will actually reach a point at which it will cavitate. This is what creates the load roar. The simple solution to this is a fan clutch, simplest ones being essentially a centrifugal system that as the rpm climbs, the coupling force drops until the fan is coasting. The next style is a thermal one, the higher the air temperature the more solid the connection is, the best (and most expensive) is a combination of the two, where with low air temperature it lets the fan idle but will cut it in if the air coming through gets hot enough. One of the issues with these, on AC equipt vehicles the fan may not move enough air for the condenser to work efficiently.

Electric fans can be controlled by modern engine computers allowing the most efficient cooling and AC performance. On FWD vehicles the fan(s) are almost always electric (Honda 600s had a belt) and since many of the engines are used in FWD and RWD vehicles, the functionality is already in the computer.

[Jacob84]

For a good alternator to provide the current needed to run a large fan at high speed the engine power consumption is probably substantially less than the power needed to turn a large 5 or 7 bladed fan. In order for a mechanical fan to move enough air at low rpm it has to have a high attack angle (blade angle in relation to a flat plane), this coupled with the fact that is overdriven by the crank/waterpump pulley ratio means that as the engine rpm increases the fan will actually reach a point at which it will cavitate. This is what creates the load roar. The simple solution to this is a fan clutch, simplest ones being essentially a centrifugal system that as the rpm climbs, the coupling force drops until the fan is coasting. The next style is a thermal one, the higher the air temperature the more solid the connection is, the best (and most expensive) is a combination of the two, where with low air temperature it lets the fan idle but will cut it in if the air coming through gets hot enough. One of the issues with these, on AC equipt vehicles the fan may not move enough air for the condenser to work efficiently.

Electric fans can be controlled by modern engine computers allowing the most efficient cooling and AC performance. On FWD vehicles the fan(s) are almost always electric (Honda 600s had a belt) and since many of the engines are used in FWD and RWD vehicles, the functionality is already in the computer.

Thanks for wiring diagrams, advice, explanations, and opinions. That’ll help me a ton as I figure out how to make my system work. And I take all that info in, I like the technicalities.

So I bought an electric fan for a Taurus. It was $12 more expensive than a fan clutch for my f150 (new, paid $47, RockAuto) so I decided to give it a shot. And considering my EFI has a built in controller it’s just wiring now. If it works and I’m happy, awesome. If it doesn’t I’ll sell it off to one of my buddies and I’ll buy a fan clutch. I don’t mind a new fan clutch, it’s cool how they work and they just work which I like.

The Taurus fan is a 2 speed fan with high speed pulling something like 2,700-3,000 cfm from what I’ve read and 33 amps. It also has a built in shroud which is pretty nice making the swap a matter of simple mounting and wiring.

As I go through the process I’ll let y’all know what I run into and how things work. I’ll record my mileage, how the truck feels, temp management, etc, before and after I install the electric fan to try and weed out any variables. That way I can come back with some sound conclusions and y’all can do what y’all want with them.

My experience won’t be the end all be all because there are too many variables like the way I drive compared to everyone else, where I drive, my specific motor, exhaust, cam, yada yada. But I’ll be able to have a decent opinion and may help the next person decide what they want to do if they have a truck like ours.

Also worth noting I’m not having cooling problems of any kind and am satisfied with my current setup. I have a 192 degree thermostat, stock radiator, stock fan, stock shroud, stock water pump (95 f150 reverse rotation). So this isn’t to solve an existing condition just a learning experience to maybe free up some efficiency and power. I’ll keep y’all posted and if y’all have input/questions/etc of any kind please post it.

[Gary Lewis]

Thanks for wiring diagrams, advice, explanations, and opinions. That’ll help me a ton as I figure out how to make my system work. And I take all that info in, I like the technicalities.

So I bought an electric fan for a Taurus. It was $12 more expensive than a fan clutch for my f150 (new, paid $47, RockAuto) so I decided to give it a shot. And considering my EFI has a built in controller it’s just wiring now. If it works and I’m happy, awesome. If it doesn’t I’ll sell it off to one of my buddies and I’ll buy a fan clutch. I don’t mind a new fan clutch, it’s cool how they work and they just work which I like.

The Taurus fan is a 2 speed fan with high speed pulling something like 2,700-3,000 cfm from what I’ve read and 33 amps. It also has a built in shroud which is pretty nice making the swap a matter of simple mounting and wiring.

As I go through the process I’ll let y’all know what I run into and how things work. I’ll record my mileage, how the truck feels, temp management, etc, before and after I install the electric fan to try and weed out any variables. That way I can come back with some sound conclusions and y’all can do what y’all want with them.

My experience won’t be the end all be all because there are too many variables like the way I drive compared to everyone else, where I drive, my specific motor, exhaust, cam, yada yada. But I’ll be able to have a decent opinion and may help the next person decide what they want to do if they have a truck like ours.

Also worth noting I’m not having cooling problems of any kind and am satisfied with my current setup. I have a 192 degree thermostat, stock radiator, stock fan, stock shroud, stock water pump (95 f150 reverse rotation). So this isn’t to solve an existing condition just a learning experience to maybe free up some efficiency and power. I’ll keep y’all posted and if y’all have input/questions/etc of any kind please post it.

I like that approach - not solving a cooling problem, but just seeing if it will work and what you think of it. 👍