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electric radiator fans  Pages: 12

mhamilton on Sat October 06, 2007 4:05 PM User is offlineView users profile

A guy on the Corvette forum was having overheating problems with an aftermarket electric fan. Said it would overheat immediately when he got on the highway, but fan was pulling air correct direction, etc, etc. He finally pulled it off and went back to an engine driven flex fan, no more overheating.

I suggested that he was blocking the air flow on the highway because the fan continued to run. Isn't is true that most (if not all) OE electric fans shut off after approx. 30 mph? I know that the air flow of the moving car is way beyond what any fan can move. There's one guy who doesn't believe me about that, but I know I read it somewhere.

Also, he said this electric fan had a shroud covering the face of the radiator. I have never seen an OE fan setup where the face of the radiator was shrouded. It just doesn't seem necessary with the fan being 1/2" from the rad, and seems to me would only block airflow.

cc61 on Sat October 06, 2007 4:23 PM User is offline

yes, most all cars electric fans shut off at around 30 to 40 mph!!

john,??? on Sat October 06, 2007 6:13 PM User is offlineView users profile

what cars do this?


none of my chevy's do, its all based on temp sensors. if your on the highway long enough or its cold enough outside that the car doesn't get to the turn on temp(10-15* above the T-stat temp), the fans stay off. even my highside ac line had a fan turn on sensor, so the fan isn't on when not needed for the ac. non of it had anything to do with the speed sensor data.


as for a shroud, older camaro's didn't have shrouded fans but the new ones do and most of us older camaro guys have swtiched to the new shrouded fans because they cool much better at idle(same part# motor's and fan blades). unless you mean he mounted a shrouded fan on the front, then yeah it could block air flow, but still.


I know in the camaro world, 99% of all over heating on the highway is because its missing the air damn under the raditor. at speed it causes a low pressure zone behind it, causing air to be sucked up and thru the rad. his car could be missing then and the stock fan is good enough to over come the lack cooling, which the electric one isn't.


cc61 on Sat October 06, 2007 10:28 PM User is offline

Not going to argue on this but almost all vehicles with obdII (96 and up) have some sort of fan shut down when the vehicles reach a desired speed

NickD on Sat October 06, 2007 11:30 PM User is offline

Fans serve but one function, additional cooling with the predominating factor being temperature. Would be nice if you provide evidence for your statement that, "almost all vehicles with obdII (96 and up) have some sort of fan shut down when the vehicles reach a desired speed."

Logically it doesn't even make sense to use road speed for fan control, example, a vehicle driving at 50 mph with a 50 mph tailwind, effective radiator wind speed is zero. Electric fans were never the best choice, 80% of the engines energy is lost in the electrical process compared to a direct engine driven fan. They do try to limit fan use using thermistors that switch the things on when either the AC or engine cooling system is just right at the edge of blowing it's cork to conserve on fuel without much concern of the component damage done by excessive thermal cycling.

I will take an engine driven fan any day.

mhamilton on Sun October 07, 2007 1:35 PM User is offlineView users profile

Okay, nevermind the question of shrouding. I'm sure it could work either way when designed correctly.

As for the fans turning off, I know I didn't think that up myself, I read it somewhere. Maybe it was on the Impala forum...

I just can't see the electric fans doing anything when the car is moving 70 mph. Seems like the incoming air would just be fighting to make the fans turn faster than the motor.

mhamilton on Sun October 07, 2007 3:20 PM User is offlineView users profile

Ah, I knew I read it somewhere! It was on the 4th gen F-body web site:

http://www.shbox.com/1/4th_gen_tech2.html#cooling

"The fans are programmed to come on when the a/c is turned on. A/c Pressure monitoring sensors feed the PCM info and depending on the situation, the PCM may command the fans off for brief periods. Also, when the car reaches sustained higher speeds, the fans may be commanded off so incoming air can flow through the radiator unimpeded and provide the cooling needed."

Also found it mentioned on another site,

http://autos.yahoo.com/maintain/repairqa/fluids_heat_air_conditioning/ques021_2.html

"In newer vehicles with computerized engine controls, fan operation is regulated by the engine control module. Input from the coolant sensor, and in many cases the vehicle speed sensor too, is used to determine when the fan needs to be on. "


Nick, I think the computer has priority controls. If the car is moving fast enough it will shut off the fans. But, if for some reason it gets to the point of overheating it will run the fans on high regardless of other parameters (at least my Impala will). Still don't have the answer to my question of whether the fans running at speed inhibit air flow. If the air flow is spinning the blades faster than the motors could, what's the point of running the motor? Would that actually cause drag as the motor would then act like a generator?



Edited: Sun October 07, 2007 at 4:27 PM by mhamilton

NickD on Mon October 08, 2007 7:40 AM User is offline

Wonder what comic book these guys get there information from, can't believe everything you read.

"By comparison, a mechanical belt-driven fan can require anywhere from 5 to 15 horsepower depending on engine speed and the size of the fan."

Try more like a quarter of a HP or less and that is when the vehicle is stopped driving an 18" fan that decreases as the vehicle speed increases. If these guys ever flew a twin engine aircraft, if say the right engine dies, it's like the right wing hit a brick wall, plane swings violently to the right and have to fight like crazy to feather that prop. On the other hand if you are flying straight and level at cruise power, push the control wheel forward a bit for a minor dive the props will spin like crazy and may even break off, go into a violent dive and the props will break off, have to watch both engine tachs like a hawk, definitely throttle back and even feather the props a tad or more than a tad.

Running an electric fan motor with the blade off can let it rev so high, the armature will fly apart, in the meantime, the current it draws is going down to zero, stall that motor and current will shoot up to infinity blowing the fuse first. The amount of load put on that motor depends the amount of air that blade has to move, at highway speeds that load decreases significantly. What really puts a load on the vehicle engine is the air resistance the vehicle is facing due to aerodynamic drag and can increase by the as much as the square of the speed or even to the cube of the speed if the vehicle is made like a square box.

Typical life of a CS-130 100 ampere alternator is around 160,000 miles in a conventional engine driven fan vehicle, in a FWD vehicle using electric fans, that life drops down to 40,000 miles or less due to overheating of the alternator and the insides are toasted, this is a viable statistic. An electric fan will freewheel at highway speeds, but does impede air flow as opposed to running. Radiator fluid temperature sensing makes a lot more sense for fan control than using the ETC in the engine as it prevents additional thermal cycling. But who cares as long as the HG lasts beyond the warranty period.

If all the BS was removed from the web, would be 90% less crap to deal with, don't believe everything you read. Oh, and make sure your condenser and radiator is debris free, that really blocks airflow, but here fan loading is decreases that the blade is running almost in a vacuum, not doing any work.

Curious about your own car, block up the driving wheels, idle the engine until the fans come on, then put the transmission in drive and watch the speedometer to see if a certain speed kills the motor. Why don't they use radiator sensing that would keep the block at a constant 195*F to prevent 195 to 235*F sensing not only prolonging the life of the engine, but less melting on the plastic stuff? Because it would cost the stockholders a couple of bucks more per vehicle, no other reason.

GM Tech on Mon October 08, 2007 8:36 AM User is offline

From the service manual of a 1998 5.7L F-car (Camaro/Firebird) here is the descriptio of the cooling fan controls

Engine Cooling Fan Description - Electric
The electric cooling fans are used to cool engine coolant flowing through the radiator. The fans are also used to cool the refrigerant flowing through the A/C condenser.

The electric cooling fans are controlled by the PCM. The PCM controls the ground path for the three cooling fan relays. The relays are used to control the high current flow to power the cooling fan motors. Both fans operate together. When minimum cooling is required, the PCM energizes cooling fan relay #1 and both fans operate at low speed, since the fans are connected in series through cooling fan relay #3. Cooling fan relay #2 is open (not energized) and is not used for low speed operation of the fans. When maximum cooling is required, the PCM energizes all three cooling fan relays. The left fan is still powered through cooling fan relay #1, but is now grounded through cooling fan relay #3. The right fan is now powered directly through cooling fan relay #2 and both fans operated at high speed.

The PCM will also enable the cooling fans after the ignition is turned off. When the engine coolant temperature exceeds 113°C (235°F) and the ignition is turned off, the cooling fans will be enabled on low speed for 150 seconds.

Low Speed Cooling Fans
The low speed cooling fans are controlled by the PCM based on the following inputs:

The A/C system.
The Engine Coolant Temperature (ECT) sensor.
The Vehicle Speed Sensor (VSS).
The PCM will turn the cooling fans on low speed when any of the following conditions exist at idle:

Certain PCM Diagnostic Trouble Codes (DTCs) are set.
The ECT above 108°C (226°F).
The A/C high side pressure above 215 psi.
Once the low speed fans are turned ON by Engine Coolant Temperature, the PCM will turn the fans OFF when that temperature has dropped about 4°C (7°F). If the low speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 190 psi. The minimum ON time for the low speed cooling fans is 50 seconds.

The cooling fans are turned OFF at certain vehicle speeds. Adequate airflow through the A/C condenser and radiator occurs with vehicle movement to properly cool the A/C refrigerant and engine coolant without the assistance of the cooling fans.

High Speed Cooling Fans
The High Speed Cooling Fans are controlled by the PCM based on the following inputs:

The A/C system.
The Engine Coolant Temperature (ECT) sensor.
The Vehicle Speed Sensor (VSS).
The PCM will enable both fans on high speed when any of the following conditions exist:

Certain PCM Diagnostic Trouble Codes (DTCs) set.
The ECT above 112°C (234°F).
The A/C high side pressure above 248 psi.
Once the high speed cooling fans are turned ON by the Engine coolant temperature, the PCM will turn the fans OFF when that temperature has dropped about 4°C (7°F). If the high speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 208 psi. The minimum ON time for the high speed cooling fans is 30 seconds.



-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mhamilton on Mon October 08, 2007 1:45 PM User is offlineView users profile

Thank you GM Tech!

Quote
An electric fan will freewheel at highway speeds, but does impede air flow as opposed to running.

Nick, do you mean that a freewheeling fan will present more impedance to air flow than a fan running on high speed (or low speed)?
Of course I am assuming this is not at any extreme speeds, say no faster than 75 mph. I know the resistance of the condenser and radiator are going to slow the air down, but I thought it would still be moving faster than the fan could ever pull it.

john,??? on Mon October 08, 2007 2:53 PM User is offlineView users profile

Quote
Originally posted by: GM Tech
From the service manual of a 1998 5.7L F-car (Camaro/Firebird) here is the descriptio of the cooling fan controls



Engine Cooling Fan Description - Electric

The electric cooling fans are used to cool engine coolant flowing through the radiator. The fans are also used to cool the refrigerant flowing through the A/C condenser.



The electric cooling fans are controlled by the PCM. The PCM controls the ground path for the three cooling fan relays. The relays are used to control the high current flow to power the cooling fan motors. Both fans operate together. When minimum cooling is required, the PCM energizes cooling fan relay #1 and both fans operate at low speed, since the fans are connected in series through cooling fan relay #3. Cooling fan relay #2 is open (not energized) and is not used for low speed operation of the fans. When maximum cooling is required, the PCM energizes all three cooling fan relays. The left fan is still powered through cooling fan relay #1, but is now grounded through cooling fan relay #3. The right fan is now powered directly through cooling fan relay #2 and both fans operated at high speed.



The PCM will also enable the cooling fans after the ignition is turned off. When the engine coolant temperature exceeds 113°C (235°F) and the ignition is turned off, the cooling fans will be enabled on low speed for 150 seconds.



Low Speed Cooling Fans

The low speed cooling fans are controlled by the PCM based on the following inputs:



The A/C system.

The Engine Coolant Temperature (ECT) sensor.

The Vehicle Speed Sensor (VSS).

The PCM will turn the cooling fans on low speed when any of the following conditions exist at idle:



Certain PCM Diagnostic Trouble Codes (DTCs) are set.

The ECT above 108°C (226°F).

The A/C high side pressure above 215 psi.

Once the low speed fans are turned ON by Engine Coolant Temperature, the PCM will turn the fans OFF when that temperature has dropped about 4°C (7°F). If the low speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 190 psi. The minimum ON time for the low speed cooling fans is 50 seconds.



The cooling fans are turned OFF at certain vehicle speeds. Adequate airflow through the A/C condenser and radiator occurs with vehicle movement to properly cool the A/C refrigerant and engine coolant without the assistance of the cooling fans.



High Speed Cooling Fans

The High Speed Cooling Fans are controlled by the PCM based on the following inputs:



The A/C system.

The Engine Coolant Temperature (ECT) sensor.

The Vehicle Speed Sensor (VSS).

The PCM will enable both fans on high speed when any of the following conditions exist:



Certain PCM Diagnostic Trouble Codes (DTCs) set.

The ECT above 112°C (234°F).

The A/C high side pressure above 248 psi.

Once the high speed cooling fans are turned ON by the Engine coolant temperature, the PCM will turn the fans OFF when that temperature has dropped about 4°C (7°F). If the high speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 208 psi. The minimum ON time for the high speed cooling fans is 30 seconds.



*right click, save as*
good stuff to know, since I have a 02 z28.


I will also add that, that year camaro has the plastic piece under the rad, without that they over heat at highway speeds. my guess is that the car that over heated on the highway didn't have this.


oh and gm tech, do you know how they make the fans run in low speed? cause I know ford fans have 3 termals, gnd, low and hi. where my gm's only have 2. + & -. I'm guessing there's a resistor pack somewhere. I have a 4th gen fan setup on my older 91 camaro too, and just don't need the fans on hi all the time.

mhamilton on Mon October 08, 2007 4:10 PM User is offlineView users profile

GM runs the fan motors in series to get low speed, and in parallel to get full speed. Need 3 relays to do this, at least the way that the factory wired it. But, the PCM has to be one that can choose between low and high. My '96 Imp has 2 fans, which the computer turns on in sequence--one fan for light cooling, then the 2nd fan comes on if the temps call for it. Here are the schematics: http://www.shbox.com/1/fan_schematic_1995.jpg

This was a '65 Corvette, so I don't think the air dams are as sophisticated as the late Camaros. I do think that something odd was happening with the air flow on his car, maybe the electric fan shroud was not designed properly (now that I know a running fan will not obstruct air flow as I thought).



Edited: Mon October 08, 2007 at 4:12 PM by mhamilton

NickD on Tue October 09, 2007 5:27 AM User is offline

Wonder if the same guy that did that GM writeup on the Vss controlling the fans that also wrote up the oil pressure switch shutting off the fuel pump?

Ford did use a tapped field winding using a coiled field rather than a permanent magnet, the tap used a small portion of the coil resulting in a weaker magnetic field causing the armature to run at a higher speed to generate the BEMF to limit the armature current. More efficient than using a resistor that just wastes energy.

john,??? on Tue October 09, 2007 12:11 PM User is offlineView users profile

wow... I feel dumb now, I total missed the series to get low speed part, it didn't click till you said it.

thanks


oh and doesn't gm turn on the fuel pump with oil press switch, not off? or am I reading that one wrong too lol.

mhamilton on Tue October 09, 2007 12:52 PM User is offlineView users profile

I'm not sure what the deal is with the fuel pump and the oil sender.

On my cars if you turn Key On Engine Off, the pump will run a few seconds then turn off.

NickD on Tue October 09, 2007 4:04 PM User is offline

GMTech knows what I am talking about from the GM truck manuals, if the oil pressure drops below about 2.5 psi, that is suppose to switch off the electric fuel pump, thing is, the darn thing isn't even wired up to do that in practice.

Yeah, you can also say the oil pressure switch turns on the pump as well as turning it off, PCM pulses the pump in run with engine off, if anyone leaves the switch in run long enough, least two seconds, motor should start, oil pressure builds up and the oil pressure switch maintains fuel pump operation. Thing is, if you are driving and lose oil pressure, that switch opens and kills the pump and the engine with it so you don't fry your engine. That is, if it is wired in to do that. PCM fires up with CAS pulses to keep the pump running, manual says otherwise as I believe GM is not using the Vss to kill the radiator fans. If they are, it's incredibility stupid. If the ECT overrides the Vss, the Vss is not even part of the equation, so why even wire it in?

mk378 on Tue October 09, 2007 5:45 PM User is offline

Most cars are not wired to kill the engine to protect it under any circumstances such as overheating or low oil pressure. They don't want the liability of killing the engine at an inopportune time. If someone runs out of oil and drives until the engine seizes, can't blame that on the car maker. And of course every blown engine is an opportunity to sell a new car.

mhamilton on Tue October 09, 2007 9:17 PM User is offlineView users profile

Now I realize what kind of people I was dealing with. This radiator/fan vendor said that his cutomer's engine oveheated because he filled the gap between the condenser and radiator, and radiator/core support. Said you are supposed to let the condenser air flow out the sides, not make it go through the radiator.

I tried to explain why you would not want hot engine air circulating back through the radiator. Got this response: ":rolleyes: whatever"

So, that takes care of that.

graeme on Tue October 09, 2007 10:18 PM User is offline

Interesting thread, would like to know the answers to a lot of these questions. I accept that what GMtech says is correct, that the fans will switch off at a particular road speed, regardless of the temperature of the coolant? , but as others have stated how does this cater for extreme situations, like the extreme tail wind in hot conditions or towing up a steep gradient not dropping below 40mph in hot conditions etc. I take it some must have witnessed this happening on a dynometer where its fairly typical for any car without an engine fan to run hot in no time?
Does a fan that is spinning in the wind cause less restriction than one that is being driven by the motor? Lot of heresay on this one?
Was chasing a cooling prob in my own vehicle(that was retrofitted with electric fans when I purchased it) on the highway and experimented with electric fans and no fans fitted at all. Found that when switched on at 60mph they were good for a couple of degrees drop in the coolant. However, their overall effect wasnt enough to run the motor at a reasonable temp, only thing that worked was putting on an engine driven thermatic viscous fan, it didnt get hot enough to thermally engage, but just the "minimal effect" of it freewheeling at highway speeds got enough airflow happening to keep the car at thermostat temp in all ambient temperatures.

NickD on Wed October 10, 2007 7:21 AM User is offline

After GM posted, checked the manual on our S-10 and it showed a three terminal oil pressure switch for switching out the fuel pump, but found a two terminal oil pressure switch in the vehicle with a two terminal vehicle connector that never was changed, came from the factory that way.

Pleased with my 04 Cavalier for a little four banger uses a huge radiator and a condenser with one tiny fan mounted in one corner, even on a hot summer day stays at 195 in traffic, fan hardly runs. DeVille uses two, two speed fans for four combinations, that sucker cycles between 195 and 230 in town, solution, don't drive it in town, too complicated to change.

mhamilton on Wed October 10, 2007 8:07 AM User is offlineView users profile

The road speed will not override the PCM if the engine overheats... if this happens the fans come on. I think the reason for the road speed sensor is so that the fans can be switched off while the temperature is above the fan turn-on limit, but the designers knew highway driving would bring it down to normal shortly. Maybe not, as Nick said, the fan "on" limit is just before the system pops.

From what I have learned, the fans will not block the airflow either running or freewheeling... at least not at the speeds that will be seen in a vehicle. It does make sense if you think that the fan will flow its rated CFM, it should allow that much air through the radiator.

I think modern cars are aerodynamic enough to have a lower pressure zone behind the radiator, such that air will always flow through it on the highway.


graeme on Wed October 10, 2007 10:28 AM User is offline

Rereading it again, think you are correct ^, which makes logical sense..........
As you have pointed out modern cars should be able to survive at highway speeds without any fan assistance as their aerodynamics have been much better looked after than older cars.....particularly flows under the car through the engine bay etc.
Perhaps the overiding message in the thread is if you have an older car or one that came standard with an engine fan, then changing over to an electric fan could cause problems as the system may not work well just using ram air, having relied slightly upon the engine fan to keep enough air going through the engine bay at higher speeds. Aftermarket suppliers of these electric fans have been pedalling this myth far too long....."a fan isnt needed or wont make any difference at speed"....unfortunately it becomes entrenched as fact in many and fit these to their cars looking for hp gains and economy improvements. As Nick has pointed out, unless you are operating the vehicle with a fixed fan in the 5000rpm+ range, then the mechanically driven fan just doesnt take off significant amounts of power. Also, the hp loss figures for mech fans are usually arrived at on engine dynos, where all the air that is stirred up doesnt make it on to the dyno reading. Thats great, if you do all your driving on a dyno, but most of us drive forwards on real roads..........and the air that is stirred up by the fan......or the low pressure area it creates in front of the rad actually is used productively in making the car move........or as Nick has pointed out the incoming air actually forces the fixed blades around reducing the load on the motor. Try out this one with a fixed blade fan on a non computerised car.........cruise at 60mph, slip the vehicle into neutral and observe the idle speed.

NickD on Wed October 10, 2007 1:53 PM User is offline

Depends upon how old your older cars are, let's go back to the 20's and 30's when the price of gas was high and even hard to find, so these small bore, long stroke, low rpm engines could burn just about anything, #1 fuel oil, kerosene, alcohol, and even gasoline. Radiators were the front of these vehicles with no restrictions, made large and robust and the fans were small two bladed affairs driven by a stapled together leather belt, a guy could make his own. Ford I, was my hero back then, Model A could cruise all day at 80 mph and still get 22 mpg, it would get you there, energy wise, GM were the bad guys convincing the American public we needed 1/4 mile dragsters and a lot more room than what we needed. We only enjoyed cheap gas prices from about 1954 until about 1972, that is only 18 years from over a hundred year automotive history.

Walter Chrysler was also a good guy but either bumped his head or started smoking crack wanting to build the world's tallest skyscraper instead of better cars.

I talked to several Ford, GM, and Chrysler dealers, yeah and also Toyota and Honda, none of these corporations ask their dealers what their customers want in a vehicle, this use to be common practice in the history books. We have experts today telling us what we want.

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