Electric fan thermostatic switch location; radiator or intake?

[derotoreut]

Originally Posted by piecesparts

Actually I would think that you would want to know what your engine is at for temperature and not the radiator. I have installed several fan switches and all of them were triggered by a sensor in the intake manifold. I feel that the best thing is to put one in and adjust it to keep your engine at a set temperature. There are some aftermarket systems that do have a connection that uses a probe that sticks into the radiator fins, or into the return hose from the T/stat, but if you want a direct and functional connection, I would seriously consider a mounting point in the intake manifold. Putting the temp probe in the head does result in false temps due to combustion heat.

I would consider it, but I don't have a place in the intake manifold. Unless I get a water neck with threaded connection I can't really do it. I am using the current place in the intake for my water temp gauge sender.

Originally Posted by piecesparts

I spent a lot of money on my engine and I put in an aftermarket radiator and dual electric fans to keep it cool. The design of the fan switch is up to the buyer, but you definitely want one to work when you need it. Cooling an engine that is cooled by water is to move the right amount of air across a finned coil that has the water in it to supprt effective heat transfer. Actually an electric fan is better than many engine driven fans for a couple reasons. The first being that the fan continues to run at the speed that it was turning at 60 MPH with the car at dead stop, thus assisting in cooling the engine faster. Also the removal of the fan from the engine provides for approximately 10 hp more power to be used in the tranmission and this gains a little gas mileage. Finally, COLD weather, the lack of a fan turning on a cold morning, will allow the engine to heat up to temp faster.

I too have spent a great deal of money on my stroker engine. I want to make sure it is cooled properly. My radiator is a custom aluminum build from Wizard Cooling. I have dual SPAL fans set up in it with a single thermostatic switch in the radiator. I'm just not sure the switch is properly located.

Originally Posted by piecesparts

My fan switch has a dual fan speed capability which turns the first fan on at a speed only necessary to keep the temp at the point that I set it for. If the temps goes up, the fan switch increases the fan's speed and then if really hot, the second fan is started to assist. I have yet to see the second fan run.

Both trucks in the attached pictures have aftermarket SPAL fan sets. The white truck has the fans behind the factory radiator and I used that truck for daily work (summer and winter driving), the black truck has a 400+ hp stroker engine behind the SPAL fans and an aluminum radiator that has been all over the country in more than one Hot Rod Power tour. I am happy to say they have supported me well.

Can you please provide me with more information regarding your fan switch set up. Is it a single switch that has the capability to turn on two fans separately? I'm wondering if I need two separate thermostatic switches to run the two fans.

[Classic Heartbeat]

Classic Heartbeat - You are answering your own argument...if the water in the engine is under 180 degrees then there is no need to cool any water in the radiator.

Why would you not cool the water in the radiator? When the water in the the engine reaches 180 it is exchanged with the radiator water. So the water in the engine is now cooled water lowering the temp of the engine. The water in the radiator is hot water and needs to be cooled off. If not the next exchange is exchanging hot engine water for hot radiator water. Why is the radiator water hot? Because the fans turned off the exact moment the exchange happens because the engine read cooler. This sets you up to at the very least an engine running hotter than it should or worce an overheating.

If it is time for an exchange, then the Tsat opens and at the same time the fans come on.

If the fans come on when the water is exchanged but turn off once the water is exchanged there isn't time for the fans to adaquitly (spell) cool the water.

If the water in the radiator was not cooled, then it would still be above 180* in the engine...and the fans will remain on.

My point exactly. Now you have set up a situation where the engine temp and radiator temp are the same. Rendering the radiator useless and setting up for overheating.

My engine sure isn't overheating...

It wouldn't as long as you are driving down the road. Then the air forced through your radiator by the simple fact that you are moving is cooling the water in the radiator. This is why people do not have problems with overheating untill they get stuck in traffic. Not moving either fast enough or often enough to keep the radiator cool.

Electric fans are designed to push or pull air through the radiator even if the vehicle is stopped. You have to have air flow through a radiator in order for it to cool the water inside. Stagnet or slow flowing air will not do it. WES

[71Sixer]

I too have spent a great deal of money on my stroker engine. I want to make sure it is cooled properly. My radiator is a custom aluminum build from Wizard Cooling. I have dual SPAL fans set up in it with a single thermostatic switch in the radiator. I'm just not sure the switch is properly located.

There is more than one way to skin a cat...it looks like the bung in the radiator is near the top which would be the hot side. You should be fine putting the switch there. When the thermostat opens and water circulates, this section of the radiator should be near the temperature at the thermostat. Depending on the efficiency of the radiator, though, it could be lower than the temperature of the water in the engine...might be splitting hairs at this point, though.

[71Sixer]

Why would you not cool the water in the radiator? When the water in the the engine reaches 180 (example) it is exchanged with the radiator water. So the water in the engine is now cooled water lowering the temp of the engine. The water in the radiator is hot water and needs to be cooled off. If not the next exchange is exchanging hot engine water for hot radiator water. Why is the radiator water hot? Because the fans turned off the exact moment the exchange happens because the engine read cooler. This sets you up to at the very least an engine running hotter than it should or worce an overheating.

Most fan switches come on at 180* and turn off at 160*...at least that is what mine does. Why would you want the fans on, if they don't need to be. I have a two core aluminum radiator with electric fans and a 496BBC. The fans never come on going down the road...and come on only when idling. I have never seen the temperatures fluctuate from the 180* mark give or take 5*. IMO with the switch located near the thermostat...the fans will only work when they need to, which is when thermostat has opened and the water that is now in the radiator needs to be cooled off. If the radiator cools the water to maintain a temperature at or below 180* (which is monitored by the switch in near the thermostat), then you do not need to waste evergy by turning on the fans.

[piecesparts]

Originally Posted by Classic Heartbeat

The fans do not cool the water or the engine. If they did we would have air cooled engines with cooling fins. So tell me how the engine temprature has anything to do with it. The fans don't cool the engine even slightly, so tell me how turning the fans on when your engine hits 180 does anything what so ever. It does not. The fans are meant to cool the water in the radiator and that is it. The cooled water from the radiator cools the engine. If your fans turn off once the water exchanges from the radiator to the engine, what is going to cool the hot water off in the radiator? It just doesn't work that way period. WES

HUH????

I am kind of confused on this one. The fans promote air movement across the radiator that cools the water and thus cooling the engine, thus enhancing horsepower, thus giving the elusion that the driver is under control of his vehicle.

Turning the fans on at 180 degrees enhances the air movement, so that is why the fans coming on is important. Once they are on, they will continue to run until the sensor picks up a temp that is at the shutdown point of the electronic control. The temperature turn on point is adjustable in many controllers, so one can turn them on at any spot in their span. The temperature in the engine is controlled by the T/stat, which cycles at a setpoint that is determined by the manufacturer, but the running of the fans at a setpoint below the T/stat cyc ling open is useless, so the factory mechanical fan is nothing but drag on the engine in that area.

Running the fans after the engine is shutdown, means that you can cool the engine by cooling the water in the radiator and the design of the system will allow the cool water to go to the engine and the warm water to exit the engine by natural circulation until the T/stat closes again. It does work, that way.

[Classic Heartbeat]

Most fan switches come on at 180* and turn off at 160*...at least that is what mine does. Why would you want the fans on, if they don't need to be. I have a two core aluminum radiator with electric fans and a 496BBC. The fans never come on going down the road...and come on only when idling. I have never seen the temperatures fluctuate from the 180* mark give or take 5*. IMO with the switch located near the thermostat...the fans will only work when they need to, which is when thermostat has opened and the water that is now in the radiator needs to be cooled off. If the radiator cools the water to maintain a temperature at or below 180* (which is monitored by the switch in near the thermostat), then you do not need to waste evergy by turning on the fans.

I use the temps stated only as examples. And your statement makes my point. There is no need for the fans to run while traveling down the road at speeds fast enough for the air to be forced through the radiator. Now think about when your engine reaches temprature when you are driving fast enough to keep the radiator cool. The fans will still turn on when your engine reaches temp because the fans sensor is set in the engine not the radiator. They didn't need to come on because the water was cooled with the air forced through the radiator while in motion.

I am kind of confused on this one. The fans promote air movement across the radiator that cools the water and thus cooling the engine, thus enhancing horsepower, thus giving the elusion that the driver is under control of his vehicle.

The fans are the air movement when the vehicle slows down. You need the fans sending unit in the radiator, so they will come on when the radiator gets hot.

Turning the fans on at 180 degrees enhances the air movement, so that is why the fans coming on is important. Once they are on, they will continue to run until the sensor picks up a temp that is at the shutdown point of the electronic control. The temperature turn on point is adjustable in many controllers, so one can turn them on at any spot in their span. The temperature in the engine is controlled by the T/stat, which cycles at a setpoint that is determined by the manufacturer, but the running of the fans at a setpoint below the T/stat cyc ling open is useless, so the factory mechanical fan is nothing but drag on the engine in that area.

Yes that is how the fans thermostat works, and your explination for the engine thermost is correct also. I think there is or has been some confusion between the two. The fans should turn on at the setpoint of the engine thermostat. Usualy 180 and should turn off at lets say 160. They have to cool the water to a temp lower than the 180 engine thermostat or the water wont cool the engine. So matching the two systoms is important.

Running the fans after the engine is shutdown, means that you can cool the engine by cooling the water in the radiator and the design of the system will allow the cool water to go to the engine and the warm water to exit the engine by natural circulation until the T/stat closes again. It does work, that way.

That is correct and why the fans sensor belongs in the radiator. WES

[71Sixer]

I use the temps stated only as examples. And your statement makes my point. There is no need for the fans to run while traveling down the road at speeds fast enough for the air to be forced through the radiator. Now think about when your engine reaches temprature when you are driving fast enough to keep the radiator cool. The fans will still turn on when your engine reaches temp because the fans sensor is set in the engine not the radiator. They didn't need to come on because the water was cooled with the air forced through the radiator while in motion.

Beating a dead horse here..My fans rarely if ever come on going down the road. They only come on briefly during warm weather at a stop - long enough to cool the water in the radiator, which in turn enters the engine at a lower temp to turn off the switch. Engine temp remains steady at 180* period. Take it or leave it.

[cubber]

I have run my switch in both the intake, and the head. I even had it down lower on the block in an I6 I had. I never had a problem with ANY of these locations. Once your t-stat opens, which it will do WAY BEFORE your engine temp gets into a dangerous range, the water is flowing through the whole system, and is probably close to the same temp. everywhere except where it leaves the radiator. I think that there isn't a nickels worth of difference in any of these positions. Your engine is water-cooled, and the water is cooled by passing through the radiator. Any sort of fan, electric or mechanical, or any sort of shroud is just a way of accelerating air across the radiator fins, thus cooling the water in the radiator more quickly. Some are more efficient methods. I too have a high dollar 383 and would not be afraid to run my switch in any of the previously mentioned locations.

[piecesparts]

That is correct and why the fans sensor belongs in the radiator. WES[/QUOTE]

I disagree, due to my experiences and what I see as having a good response to the heat in the engine. The temp switch needs to be aligned with the T/stat operation and the issue of running with the engine off becomes a non-issue. However, my fans are set to not run with the engine off, as are the factory switched fans in many vehicles.

The fan setup that I have for my next project will have the option to have a sensor in the radiator or in the intake manifold of the engine. At this time, I am inclined to still put it in the intake

[dwcsr]

Some switches are made to specifically go in the radiator. If it has a 3/8 or 1/2 inch pipe thread it is not a radiator switch. The radiator switches usually have a fine metric thread with a sealing washer or O ring.

[Classic Heartbeat]

I am just going to agree to disagree here. These aftermarket fan systoms are designed to cool the water in the radiator so when the engine heats up and the thermostat opens, the water pump, pumps the cooled water from the radiator into the warm engine to cool it down. The hot water simotaniousely is pumped into the radiator heating it up. If the fans are not reading the temprature of the radiator then they don't know when to turn on, or off to cool the radiator. The temp sensor placed anywhere else in the systom can not give an accurate reading of the temprature of the radiator where the fans are located and are what they are designed to cool. I am not saying that the other locations won't turn the fans off and on and give some cooling effect, because obviousely they will. It is just not how the systom is designed to work. If you do not want your fans to turn on after you turn your truck off, then wire them to a source controlled by the ignition. WES

[ItsRandy]

I understand what Wes is saying and it makes sense, however, IMO, the temp reference point for the fan control is not as important as everyone is making it sound, as long as the sensor for the control is matched for that reference point or your control is adjustable.

The water coming out of the engine effects the temp of the radiator so a sensor in the radiator will work fine. Because the water coming out of the engine effects temp of the radiator, a sensor in the area "below" the thermostat, in the intake manifold, will work fine also. Because the water that circulates in the head effects the overall temp of the water in the cooling system, a sensor in the head will work fine, however, the temp rise in the head happens much quicker (close to combustion chamber) so you would need to keep this in mind when designing your fan control system or your fans would come on very early.

Because the water coming out of the engine does not effect the temp of the tailgate, a temp reference point for the fan control at the tailgate will not work fine and should be discouraged.

[Classic Heartbeat]

Because the water coming out of the engine does not effect the temp of the tailgate, a temp reference point for the fan control at the tailgate will not work fine and should be discouraged.

Well said. WES

[piecesparts]

What ever each wants to acheive an understanding. The point of reference for cooling is the engine and if you sense it at the radiator or the engine, it does not matter, however, the fans can be tied to the engine for a more direct effect to the process.

[71Sixer]

For the sake of science and proof, I have attached a video of my engine after a cruise and sitting idling for a few minutes. You will be able to see the temperatures during fan operationg using an IR temperature sensing tool. Case in point - the fans will work just fine with the temperature sensor located near the thermostat in the intake. Take it for what it is...

http://www.youtube.com/watch?v=Ze76k...ature=youtu.be

[derotoreut]

Originally Posted by ItsRandy

Because the water coming out of the engine does not effect the temp of the tailgate, a temp reference point for the fan control at the tailgate will not work fine and should be discouraged.

This is awesome. I love it. Great comments and opinions.

[fattyarbuckle]

c'mon children.....

what do you want to keep cool? The engine or the radiator?

I would say the engine is what you want cool......,.
so with that said, why would you put a sensor or fan switch in the freakin radiator?????

tHE BEST PLACE IS THE HEAD.....NEXT BEST IS HOTTEST POINT IN ENGINE. (NEXT TO T-STAT)

[derotoreut]

Originally Posted by fattyarbuckle

c'mon children.....

what do you want to keep cool? The engine or the radiator?

I would say the engine is what you want cool......,.
so with that said, why would you put a sensor or fan switch in the freakin radiator?????

tHE BEST PLACE IS THE HEAD.....NEXT BEST IS HOTTEST POINT IN ENGINE. (NEXT TO T-STAT)

I don't think I will do this for a couple of reasons. First is due to my headers and heat soak in this area. I just don't believe mounting the thermostatic switch in this location will give me an accurate reading. Due to the high temperatures from the exhaust and headers I think my fans would run constantly from heat soak, which leads to the second reason. The fans are there to help control the water temperature in which cools the engine. IMO the best locations appear to be in the radiator or intake manifold. I don't even think I would consider the head location for my 383 application.

[volksworld]

the original question on this thread was what was the BEST location for the fan switch.WES is 100% correct in his explanation.the reason fan switches are available for the engine is that chevys have half a dozen threaded holes on the engine and zero places to mount one on a stock radiator.will it work on the engine? of course it will. Will it work more efficiently on the radiator? yes it will. will it cut your fuel mileage in half ,rob you of 50 horsepower and make your engine explode? of course not. Saying you must be correct because you havent had a problem is like saying you dont need disc brakes because youve never rear ended anyone and timing lights are stupid cause youve always tuned your car by ear and it hasnt blown up yet.

[Andy4639]

Originally Posted by derotoreut

I don't think I will do this for a couple of reasons. First is due to my headers and heat soak in this area. I just don't believe mounting the thermostatic switch in this location will give me an accurate reading. Due to the high temperatures from the exhaust and headers I think my fans would run constantly from heat soak, which leads to the second reason. The fans are there to help control the water temperature in which cools the engine. IMO the best locations appear to be in the radiator or intake manifold. I don't even think I would consider the head location for my 383 application.

My personal opinion on the headers, heat soaking the head and making the senor read bad is doubtful to much air space between the two other than the flange of the header.
The only thing I want to add is the factory temp senor is on the drivers side head between #1 & #3 spark plug, this is where GM says they need to be anyway on a 71 Chevy truck.
You can see the wire going to it in my picture. The little wire by #1 plug wire.

[dwcsr]

I still don't get the radiator theory. One thing we know is that the radiator is a passive heat exchanger. It can only cool with or without a fan, it can't heat or make the engine water hotter than it is when it comes out of the Tstat housing so why would we care what temp it is, it can't be any hotter than the engine it can only be cooler. So why would we want to sense the water at a cooler point in the system than at the highest point. The sensing point should be at the Tstat outlet or cylinder head where ALL the heat is generated. Most all GM switches are set to work in the engine.

As for the heat soak issue on a switch it rarely happens. I sell hundreds of switches and fan kits a year and rarely does any one come back and say the temps are off. If it does happen its when the header tube is within 1/2 of the switch or the header flange between tubes is within a 1/4 inch of the switch. This can be solved by a sheet metal sheild or a spark plug sock. The stock chevy 67-72 like my own has the sheild already. I have one in the head and one it the mainfold for a Mark8 style fan

[derotoreut]

Originally Posted by Andy4639

My personal opinion on the headers, heat soaking the head and making the senor read bad is doubtful to much air space between the two other than the flange of the header.
The only thing I want to add is the factory temp senor is on the drivers side head between #1 & #3 spark plug, this is where GM says they need to be anyway on a 71 Chevy truck.
You can see the wire going to it in my picture. The little wire by #1 plug wire.

True, the factory temp sensor is located on the driver side head, but the factory sensor is a temperature sender for a water gauge not a thermostatic switch used as a signal for electric fans. So if you have your temperature gauge sender installed there where would you install a thermostatic fan switch?

[71Sixer]

will it work on the engine? of course it will. Will it work more efficiently on the radiator? yes it will.

I keep hearing this, but am not seeing or hearing any quantitative proof.

I still don't get the radiator theory. One thing we know is that the radiator is a passive heat exchanger. It can only cool with or without a fan, it can't heat or make the engine water hotter than it is when it comes out of the Tstat housing so why would we care what temp it is, it can't be any hotter than the engine it can only be cooler. So why would we want to sense the water at a cooler point in the system than at the highest point. The sensing point should be at the Tstat outlet or cylinder head where ALL the heat is generated. Most all GM switches are set to work in the engine.

As for the heat soak issue on a switch it rarely happens. I sell hundreds of switches and fan kits a year and rarely does any one come back and say the temps are off. If it does happen its when the header tube is within 1/2 of the switch or the header flange between tubes is within a 1/4 inch of the switch. This can be solved by a sheet metal sheild or a spark plug sock. The stock chevy 67-72 like my own has the sheild already. I have one in the head and one it the mainfold for a Mark8 style fan

Well put.

[dwcsr]

Originally Posted by derotoreut

True, the factory temp sensor is located on the driver side head, but the factory sensor is a temperature sender for a water gauge not a thermostatic switch used as a signal for electric fans. So if you have your temperature gauge sender installed there where would you install a thermostatic fan switch?

The other head or intake

[derotoreut]

After reading all the posts and trying to be objective about everyone's opinions, I think I'm going to place the thermostatic fan switch in the radiator. The radiator fabricator welded a coupling into the aluminum radiator for this reason, and I really think it will function properly in this location. Since I have dual electric fans, I may even install a separate switch in the intake to independently control the dual fan operation. I'm not so sure that this will make a big difference, but it will interesting to try. I definitely don't like the idea of locating the fan switch in the head, but again that's my opinion. Will the fan switch located in the head turn the fans on and off? Of course they will. Will they run more then they should? IMO I believe they will. Plus for my 383 stroker application with aluminum racing heads and headers, I just don't like the idea, especially if I can get the same or better result by locating it elsewhere. Again the purpose of the thermostatic switch is just to control the operation of the fans. It needs to sense the temperature of the cooling water to be able to turn the fans on and off; and if the water gets too hot at the radiator then additional cooling is needed. Originally this post asked the question of whether the fan switch should be located in the radiator or intake, because honestly I didn't really think it should be installed the head (for MY application). I really appreciate everyone's input and that's what makes this site so awesome.