Electric fan controller

[Slammed67]

For those of you who don't check the review board regularly (like me), I posted a review of an electric fan controller that I recently installed. You guys/gals with electric fans might want to check it out.....

http://67-72chevytrucks.com/vboard/s...threadid=69772

[Bowtiefreak]

I got basically the same thing from Flex-a-lite for my Chevelle and it works great also. Derale makes good stuff too.
Thanks

[Classic Heartbeat]

I am curious... I have been in discussions about these thermostats installed in the blocks verses radiators before and I don't want to start an argument. Just give food for thought.. What does the engine water temperature have to do with the cycling of the electric fans that are cooling the water in your radiator? The temperature that matters to the fans is the temperature of the water it is trying to cool,,, and that is in the radiator..... It seem like to me, if you're fans are coming on at lets say when your engine water heats up to 180deg., then your 180deg. (engine) thermostat opens up, and the water pump pumps that 180deg. water out into the radiator. Write? Now this is where the problem comes in. The 180 water is now in the radiator, where it needs to be to be cooled off by the fans. Write? Well the (example) 90deg. water that was in your radiator is now in the engine. That is the way it is supposed to work. Well what happens when your 90deg. water hits your 180deg. (fan) thermostat? Well if it is working properly, it will shut off your fans, because the (fan) thermostat says the water is now cooled off.... When in all actually the water in your radiator (where your fans are trying to cool it) is still 180deg. and your fans are off. They are off untill the water temperature in the engine is back up to 180, where we start the cylcle again. Only now we are replacing the water in the engine with the uncooled water in the radiator. Sounds like a recipe for overheating the engine to me. At least in heavy traffic or in town driving... Anyway, this is just food for thought and it seems like the electric fan manufacturers are selling products that sell because the instalation is cleaner, but can't function correctly.. Am I wrong on this?? WES www.ClassicHeartbeat.com

[crazy longhorn]

Wes, that is a good point that you brought up.I havent installed the controller on my fans yet(still running on a toggle). I like the cleaner look of the manifold or head installed switch. This is mosty speculation on my part, but i think the fans need to be set to "kick" @ a higher temp with the switch in the manifold/or head vs the probe in the radiator. I have my temp guage in the intake manifold, & like to see 185-190 on the guage to keep the aluminum headed sb running at its best.......the temp in the cyl heads may very well be 200-210. You will also find the temp slightly different from one side of the rad to the other. I think its just a matter of setting the controller to kick at a higher temp if its measuring coolant temp in the engine itself......the coolant in the radiator will be cooler than in the block/heads(no doubt). I would like to hear more thoughts/opinions on the subject myself. crazyL

[Classic Heartbeat]

Well you problem right on the engine water temps. However even if there is lets say 10 degree temp difference from one side of the radiator to the other, it is still going to be the only reading that should determine when the fans come on. I'll give an example... Lets take your scenario and say we have installed a fan thermostat in the intake or head and set the temperature at 195deg. (example only) Well even if you have a 200 degree engine water temperature thermostat, where the water stays in the engine for a few minutes longer before it exchanges, you will still have over heating issues, especially in the heavy traffic or in town driving, where you do not get much air exchanged while moving down the road. Why? Because you are not measuring the temperature of the water you are trying to cool off. It would be better to set it for a lower temp. because at least your fans will run long enough to cool the water in the radiator before it gets exchanged for the hotter water in the engine. Of coarse then your fans might run all the time, eliminating the need for a thermostat all together. Which incidentally that is what you are doing by locating it anywhere but in the water in the radiator. I am not trying to be smart with this comment, but you just as well as dangle the fan thermostat out on the antenna.. It will be just as effective out there as anywhere else that is not the radiator... Anywhere else is just guess work and wont function the same in different scenarios... In order for it to work the same in all situations, it needs to be in the water that the fans are cooling. The bottom line is that your engine is cooled by the water that is in the radiator, and any other cooling that the engine gets is strictly incidental. The fans are designed to pull air through the radiator and not blow air across the engine to cool it. (This is what I mean by incidental) This is why I feel like the manufacturer of the in the head, manifold or firewall (just kidding) is just out to get your money for no good reason. I defy anyone to write flex-a-lite, or derale and get there expert opinion on it. It just can not be any other way... It just is not physically possible. I guess there would be one exception to the rule, and that would be to eliminate the engine thermostat. (The one that opens up to exchange the water) WES www.ClassicHeartbeat.com

[crazy longhorn]

When we measure coolant temp,its in the manifold, or at the cyl head. That measure needs to remain constant......at the cyl head will be a little hotter. from the top of the intake, to the rh side of the rad there will be a little difference, but not too much from what I have seen. from the factory, the switches are in the in the intake on many vehicles......but the fans dont "cut in " till about 230 on the temp!(GM & Ford both) A little high if you ask this crazy old man, but it must work, as all those stocker would not live if they ran too hot. i think if you can get the fans to switch off/on, & maintain a constant temp at the guage(I run autometers), it shouldnt be a problem. Cooling is something that i know a little about.....not a lot tho! The temp guage reads the heat of the coolant while its in the engine.....I guess my thoughts are if that reading stays where it should be , its ok? Im still not sure about cut in /cut out points on that fan set up on the head or manifold sensors......one of those deals, where i have thought a lot, but havent sorted it out! At any rate, I dont look to cause an arguement , but am willing to learn more crazyL

[Classic Heartbeat]

No argument crazy longhorn, just a good debate. I don't take offence to anything that you are saying as I hope you aren't me. I also agree that you need to know what your engine temp. is, but that is only an indicater of how or what your engine is doing. If it is running too high or too low, it indicates you have a problem somewhere that needs to be addressed. The fan thermostat, however serves a completely different function, and that is to tell the fans where to come on and when to shut off. Thats it.. If your engine temp. is high (as indicated by the temp gauge in the truck), it could be for a variety of reasons including the electric fans not functioning as they should for whatever reason, but not exclusivly. You see what I mean? Your fans turn on for the express pourpose of cooling the water in the radiator and that is it. (Not to cool the engine.) The water that the fans have cooled inside the radiator is pumped inside the hot engine, thereby cooling the engine. When the hot water is pumped into the radiator, that is when the fans need to come on and cool that water. Only if the water in the radiator is cooled befor it exchanges in the engine will the engine be cooled by it.
Good debate huh!! WES www.ClassicHeartbeat.com

[MOTHERTRUCKERS]

Lots of good points here, I run the probe inside the top hose about 6 inches (heat rises) . It makes no sense to me to put a probe on or in the fins on the outside or in the intake or head. BTW mine has the metal line from probe to adjustable thermostat not the wires.

[Jwill41]

Wes, I have been in several of these "discussions" about the electric fan controller. I agree with you 100%. You must cool the water that is in the radiator so that is where the controller should be. I am running a Hayden 16" fan with the radiator controller and have absolutely no problem.

[crazy longhorn]

Yes, a very interesting topic of discussion! I would call the radiator a "heat exchanger", basically there to rid the coolant of the excess heat. On the stockers (stock fan ,ect), I have seen a difference of about 20 degrees from the cyl head, to back into the engine. One of the wildest things i have seen is dual fans dont need to run much in the 95-100 degree heat ......if my truck is moving! If she is sitting still, or I have the throttle opened up, they do need to run quite a bit. On the road, there is plenty of airflow through the radiator to keep the temp in that 185-190 range. Waterpump speed also is a factor......running through town (slow), I may run in 5 th gear to keep the pump speed up. She runs cooler that way. My truck does have the big 4 row core, & has never been an overheat problem. As far as how to switch the fans, I still need to learn more.....but am very pleased with the dual elect fans(also the extra power they free up!) From a plastic flex fan, to electrics......you can feel the power! crazyL

[Classic Heartbeat]

That is verry true crazy longhorn... the electric fans do free up some extra ponies... They also allow my Big Block to respond quicker to my foot... Hehehe!! WES www.ClassicHeartbeat.com

[Longhorn Man]

Wes, I agree with you on cooling the water in the rad, and controling the fans from the temp in the rad, not the engine temp.
I have mentioned this in the past and got flamed for it so i shut up.
Same with having the fans wired directly to the battery. Once the engine is off, it doesn't matter if the fans are on or off, the engine will not benifit from it.
But I bet Die Hard likes them wired up like that.


Again, I thin you are righ about the aftermarket making something that will sell, even if it's functionality is questionable. Otherwise, the triangle foam air filter and flex fans woulda been taken off the shelves years ago.

[Slammed67]

Correct me if I'm wrong, but aren't we trying to control the engine temperature, not the radiator temperature?? The fan will cycle on and off to keep the engine temperature constant, not the radiator temperature. I look at it like this...... is your home thermostat located in the room or is it in the main duct work? It's in the room because you are trying to keep the room temperature at a certain temperature, not the duct. I know it's a different type of system, but I think it follows the same principle. Like Crazy said, my fan hardly runs at all while the truck is moving, actually don't think it has come on yet. It only comes on when the truck is at rest.

Also, I'm pretty sure the coolant is constantly flowing through the engine and radiator once the engine gets to operating temperature. It's not like the thermostat will open and close instantly. Therefore I don't see how there will be such a difference in temperature between the radiator and the engine. In your example, you talk as if the thermostat slams shut, the fan cools the water in the radiator, then the thermostat slams open and dumps cold water into the engine.

I only have the stock temp gauge in my truck so i don't know the exact engine temp. I know about where the gauge reads while I'm driving, so I have the controller set to keep it at that temperature while the truck is at rest.

Therefore I really don't see why it matters where the probe is, as long as the fan can maintain the engine temp.

I work for an engineering company....... maybe I can ask one of the Mechanicals for his opinion

[Longhorn Man]

If you were to get one of those little lazer temp probes, you would see that the thermostat does indeed continue to open and close throughout the time you drive your vehicle.
That is why running without an t-stat can (and does) cause overheating.

[crazy longhorn]

I dont think there is a right or wrong way to control the fans(both ways should work). Basically, i do agree that we are controlling the coolant temp in the engine(not the radiator). the radiator/fan(s), thermostat & water pump do that job. If the system is in shape, the coolant will cool down somewhat just by running through the radiator.....even tho there is no fan. On the road, there is plenty of airflow, & the fans work very little. the thermostat is for fast warmups, & serves to keep the coolant at a more constant temp(big fan+ road speed= cooler temps) , in that case the stat needs to close to keep the temp up.....back up to temp & it opens to keep things cool......its not a fast open shut deal, & may be at times partialy open. How fast the coolant circulates is another factor. As a rule, i have seen them run cooler with faster waterpump speed(moreso in town), but the faster pump speed doesnt seem to hurt on the road. I have played with pulley sizes on the waterpump to come to this conclusion......spin it too fast, & a pump driven fan will "eat" a lot of power, but i havent seen an overheat problem . crazyL

[Slammed67]

Does it close completely though? I just don't see how there is THAT much difference in engine/radaitor temp.

[Classic Heartbeat]

Slammed67, Look at it this way. The only reason you have a fan is to pull air through the radiator. Not to blow air across the engine. Air across the engine is a by product of pulling air through the radiator. If the engine was air cooled, it would have cooling fins on it, so it is strictly water cooled. So how do you cool the water? You can't cool it in the engine while it is running, it is being heated up. The engine thermostat does open and close and it does shut the water off completely. If you want to see how fast, take one and put it in a pot of boiling water and watch it. It does open fairly quickly. Then drop it in a pot of cold water and watch how fast it closes. It may leak a little water past, but the amount is insignificant unless it is worn out. So think about it, if the fans come on when your engine reaches 180 and then the engine thermostat opens and lets the hot water out, and the cool water in.... What will happen? If the fan thermostat is in the motor, once it sences the cooler water in the engine it will shut the fans off. Even though the water in the radiator is still 180 or hotter. Now if your sitting in a traffic jamb and your engine heats up again, once the engine temp gets back up to 180 the water will exchange again, only now it will do it with uncooled water from the radiator. Now you have 180 in the engine and 180 in the radiator and now sure the fans will come on, because everything is 180, but that is the only reason. The water in the radiator must be cooler than the engine to be able to cool the engine... That only makes sence.... So keeping that in mind, why would you put the thermostat for the fans in the engine? In the case of your thermostat in the living room and not in the duct work, just confirms what I have been saying all along.. The thermostat is in the room, because you are trying to control the temp. in that room. The same is true with the radiator... The electric fans or any fans for that matter are controlling the temp. of the water inside the radiator.... The cooled water is what is controlling the temp. of the engine. not the fans... WES www.ClassicHeartbeat.com

[crazy longhorn]

Thanks for that link Slammed67....I have talked with one of the tec guys at Derale, & I plan to run the same setup crazyL

[Broken_down?]

The electric fans or any fans for that matter are controlling the temp. of the water inside the radiator.... The cooled water is what is controlling the temp. of the engine. not the fans...

So the fans are whats cooling the water, and the water is cooling the engine. cool. ok I got a question about that. So the dual fans keep things cooler. I was wondering if I put dual fans on and a switch to turn the 2nd fan on @ will but also turn on when needed by the actuall cooling process, will this actually cool the water anymore then just 1 fan? or is it more a burden then needed.?

question 2.

If I put a lower temp thermostat in say 160◦, it will shoot the water into the block when the temp hits 160◦. so that means the water will be 160◦ when enteriing and cooler when leaving. Now here is my question. Would the dual fans cool the water even more?

question 3.

How fast the coolant circulates is another factor. As a rule, i have seen them run cooler with faster waterpump speed(moreso in town), but the faster pump speed doesnt seem to hurt on the road. I have played with pulley sizes on the waterpump to come to this conclusion......spin it too fast, & a pump driven fan will "eat" a lot of power, but i havent seen an overheat problem . crazyL

So a faster water pump put the water through quicker. By putting a small diameter pully makes the pump turn faster there by moving water faster. ok so If I put a small pully on the pump will that actually make any difference? Or wil it put more wear on the belts then needed??

question 4.

back to the fans.. A bigger fan will cool water quicker? if this is correct then putting dual BIG fans will make water super cool? right?


This was a beatiful post. I was just asking some buddies about this same topic.

---Broken_down?

[Classic Heartbeat]

Answer to #1)
It will probly bring the temp. down more that way, but I question the need for it. It seems to be a lot more work for something that has questionible benifites. I know people will wire that one of the fans will come on when they turn on their AC, but that is for other reasons though.
Answer to #2)
I am not sure what you are asking, but this what I think you are anyway. It is the thermostat for the engine temp. that causes the whole process to begin. So if you put a 160deg. thermostat in your engine, then you need to set your fans at or about 160 also. Set it hotter and the fans wont come on, the cooler you set your fans, the cooler they will cool the water befor they shut off. You don't want the water too cool because the engine is more efficiant at around 180 or even a little hotter.
#3)
I also question the need for a faster water pump. It just doesn't take that long for the water to exchange from the engine to the radiator. It is probably benificial for race cars, but questionable for street.
#4)
Bigger fans don't always equate to more CFMs., but as a rule they do. So it is important to check the CFM rating of any fans you buy.
Duel big fans will cool the water faster but not necessalily cooler, because it is the thermostat setting that will determen when the fans shut off, so the size wouldn't matter in this case. Bigger fans would probably shut off quicker though, but they will also be a bigger draw on your battery.

WES www.ClassicHeartbeat.com

[Broken_down?]

nice. thx for the the input. one more question. how do I set the fans for higher temp orlower temp? it is a fan on a belt. Or are you talking electric fan? ( I am new to trucks so bare with me )




Broken_down?

[crazy longhorn]

The faster waterpump speed helps more with low speed cooling, or while sitting in traffic on those 100 degree days, when there is not much airflow through the radiator. the radiator needs airflow through it to cool things down......it doesnt really matter if by fan or ram air cooling(driving down the hyway). I run my longhorn through town in 4th or 5th gear(depending on traffic speed), to keep the pump spinning a little faster......then the fans dont need to run. # or 4 gears @ 6000 rpms, & the fans run plenty tho! I have 2 - 14" flex a lites on a hand built shroud. they fit pretty much back to back on the shroud, with about a 1/2" strip in the center(also i have a stiffener welded into the back). The 2 fans are said to pull 2700 cfm as a pair. here is a link on waterpumps/cooling..... http://www.stewartcomponents.com/ lots of good info.....crazyL

[Classic Heartbeat]

To answer your question about how to set the temprature for the fans. I was talking electric fans and those have adjustible thermostats. (at least the ones that I sell do.) WES www.ClassicHeartbeat.com

[adamls]

From an engineers perspective:

All heat exchangers are built to control the temp of the fluid as it leaves the exchanger (radiator in our case). No matter what the volume, speed or temperature of the fluid coming in (water in our case) the exiting temperature should remain constant. This is acomplished via more or less coolant (air in our case) across the exchanger. It is the thermostats job to keep the temp in the engine constant. It is the fans job to keep the temp of the water leaving the radiator constant. The best way to control the fans would be to measure the water as it leaves the radiator or just before it enters the engine before it accepts any heat from the engine. So a probe in the radiator would be fine as long as it was as close as possible the outlet of the radiator and a probe in the engine would be fine as long as it was as close as possible to the inlet of the water to the engine.