put a capacitor on e-fan?
 

I just upgraded to a FD alternator and the voltage is still a bit low especially when the fan kicks on... would it be beneficial to install a capacitor for the efan so it will drain that energy source when it kicks on? just trying to think of some ideas...

I think it would work. If the music amps use it when the bass kick hard, and some electrical motors use capacitors to the start kick, why would not work with a e-fan?

none of the electrical guru's have a take on this?

it would only creat a benifit RIGHT when it kicks on, causing less of a dim right when it turns on. while the fan is running runing your voltage will stay low as its a constant current draw once its spinning at speed. a capacitor only acts to smooth out sudden changes in power. so if thats what you desire then it may help.

The capacitor will only prevent the initial drop in voltage when the fan first powers up, it won't help with a low voltage problem when the fan is running.

Instead of a capacitor, why not just use a variable speed fan controller? Something like the Spal PWM controller (I have one sitting on the shelf waiting to go into my car) will make the e-fan behave more like the stock clutch fan. It will run the fan at a low speed once the car reaches temperature, and then ramp the fan up as the temperature of the car increases. It avoids that nasty current spike AND leads to more even cooling. You'll probably only spend a little more money on the controller then you would have on a decent capacitor.

thanks guys that extra info on capacitors makes sense and is not what i am looking for... aaron ill look into that and see if my black magic can use that

The Spal controller is two-speed only, i.e. 50% at the first temp set-point and 100% at the second set-point, and it does nothing to limit in-rush current. It actually runs the fan at 100% for the first half-second of operation before dropping to 50%.

The Flex-A-Lite VSC fan controller works the way you described.

NZ-Aaron is correct, the Spal PWM does in fact vary the speed of the primary fan between the low temp setting and the high temp setting. The verbiage in the SPAL marketing blurbs and the installation manual are poorly written in an ambiguous manner, leading to many discussions and incorrect conclusions.

Here is a post (from another forum) from the Spal employee who co-designed the system.

I realize that this read alone may leave questions, but the post was a response the another poster that expressed the exact same claim that the PWM would not vary the speed but instead have a two speed effect.

Here is a link to a vendor that post's Spal's internal clarifying memo to
distrubutors. The problem addressed is that the fans never seem to turn off in use.

http://forums.corvetteforum.com/show...9&postcount=27

That's not true (about the Spal controller). I spoke to the Spal rep at Autorama last year for about 15 minutes (much to his annoyance) regarding the controller. It's supposed to work as such:

-upon reaching first set point, the fan is momentarily run at full speed for 2 seconds to get it going. This is going to cause the current inrush, so you are correct in that the controller won't solve this issue. The fan then "idles" at 50%.

-as the temperature increases, the PWM duty cycle goes up until it is at 100% at the 2nd temperature set point

-as the engine cools, the fan continues to run at full speed until the temperature has reached around 15 degrees (F) lower then the high setpoint, at which point the fan slows down. I may have that number a little off but you get the idea.

However the instructions will have you set up the controller very strangely. They want you to start the low setpoint 10-15 degrees below the point at which the thermostat opens and then set the high setpoint 20 degrees hotter then thermostat temperature. I have no idea why, and it sounds like a poor way to set the controller to me...

I took a look at the FAL controller and it seems typical of FAL stuff. Plastic, lacking weather tight connectors, probe that gets pushed into the radiator fins. Based on my previous experience with FAL products failing at an alarming rate it would not be by first choice. :)

I have a spal PWM in my chevelle, colorado and 7. As NZ said, it goes to full speed when first turned on and then shuts the fan off or runs it at low speed. Now what I don't know is what happens once the car is up to temp and it actually begins cycling between off/low/high. I could see it ramping the voltage up softly in those instances.

Aaron-the intent, according to the link I posted is for the fan to run nearly all the time at least at the 50% setting. Then as needed, the speed increases. This in effect mimics the engine driven viscous clutch fan operation. The majority of wear on the fan motor is to the brushes and most of that (they say) happens at the inrush current. They believe that the fan running at 50% speed will yield less wear on the brushes than cycling the fan off and on. This is the reason for setting the low temperature set-point slightly above the t-stat temp.

Regarding the electrical current used at 50% speed: I am not an engineer, but have a little training with air movement, fan and motor selection for industrial and agricultural ventilation. Using a fan law calculator tells us that if you have a Black Magic 150-15" fan pulling 13.9 amps turning 2200 rpm moving 2800 cfm and you run it at 1/2 speed, 1100 rpm, you will move exactly half the air-1400 cfm, but you will reduce the running amperage from 13.9 amps to 3.75 amps. Not a bad deal.

have you checked all your ground points????? or do u have some 24ga thread for wire going to your fan..what are u taken the voltage with a meter at the battery and at the fan? anything under 12.5 volts means u got a problem and it should read 13 or more with the alt kicked on

I guess I stand corrected. :bigthumb: I reseached this unit a while ago, and the instructions say:

"When the Low setting is reached the yellow LED will light and the fan will run at 100% for 1/2 second to get the fan rotating. After the initial kick-start, the fan will run at 50%, or 1/2 speed. When the High setting is reached the red LED will light and the fan will run at 100%, or full speed, until the engine cools to the point that the fan can lower its speed."

It says nothing about varying the speed between 50% or 100%. Not a great way to market a product, but I guess this improves my opinion of the product. ;)

Yeah, I'd definitely ignore that BS. The fan would run constantly, which is the dumb-ass way to operate an e-fan...

No, the stock fan doesn't run nearly that fast when the clutch is not engaged. Spin the stock fan when it's stone cold and you can feel that there's nowhere near enough "pre-engagement" for the fan to reach any worthwhile speed. I bet you'd find at highway speeds the fan is turning mostly because of the air being pushed through it rather than input from the engine.

Maybe they have a low opinion of their own fans' longevity. OEM fans are never run continuously, and they last for forever. :)

The instructions are very poor and confusing. Probably written by marketing people instead of those who designed the product.

I plan to cheerily ignore their advice on where to set the high and low point, and will set my low point around 86 degrees with the high point somewhere around 100.

Also I'm going to replace the cheap (obviously made in China) WeatherPack connectors that came with the unit with quality (Canadian made) Delphi/PED WeatherPack...

Without a lot of math and physics involved:
All motors should be started on the full or highest setting then dropped down to a lower setting.
Starting motors on a low settings takes more energy to get the motor running up to speed (even on a low speed) than a initial high burst of energy. Running motors at turn on at a low setting also plays hell on the coil windings causing them to heat up quickly thus, a early failure of any motor.

Imagine turning on a ceiling fan or big window fan. Which would move air fastest?
Starting the fan on high and stepping down the speed? Or starting it on low and waiting for those big blades to spin up? Obviously low is gonna take some time.
Yes, these are A.C. motors and e-fans are D.C. but the effect is still the same.
The controler Arron talked about sounds like a good idea because of the way the controller sends energy to the motor at start up then afterwards.
Adding a capcitor to this controller would proly burn up the fan or controller.
Adding a capacitor otherwise will no doubt blow a fuse. Capacitors on audio systems are wired a bit different then a fan.

Math and physics of motors? Try this.
http://www.physclips.unsw.edu.au/jw/electricmotors.html
Have fun!

i was having the same problem so i bought a thermo switch and set it to my own desired temp and it would kick on when it reached it then kick off ...so it wasnt on constantly. then i installed an fd alternator it runs mint with everthing on...

I've been looking at this thread with interest since my single taurus fan is destroying relays and runs to much. I did install an FD alternator, but I fear the fuel pump might get starved.

I looked at the Spal web site and I noticed the
Temperature sensor for use with the SPAL FAN-PWM
-3/8-inch NPT thread

Will this fit our RX-7s?

im using a 94 ford escort fan it looks like it belongs with the car i have a thermo sensor on a relay with overide my fd alternator made a big differance for me this set up works all day long with stereo heater etc ..the secret is the thermo sensor and fd alternater for me...

If the relay is getting destroyed they you need a bigger one. If the fan runs to much you have the temp switch set wrong.

Why? :Wconfused

i actually considered running a capacitor also for my fan. its a Taurus fan and definately draws a lot of power. i have the same problem of the slight stumble with the fan on, but i use my microtech to richen up the fuel map to compensate for the sudden lack of power running to the fuel pump

Without a lot of nitpicking analysis, it apparent that you either have a very limited understanding of electricity in general and electric motors specifically or you have a good understanding but a very limited ability to explain complex concepts in simple, but accurate terms.

You should also learn to use spell check.

You have fun too.:)

i just finished installing the spal PWM with an 18" ford fan and with everything on( supra pump, hid's, and fan) the voltage is at a healthy 14.0 volts. i have an FD alternator which i am glad i got. with the hid's off volts read 14.1. i have yet to measure amperage draw when fan kicks on. i am also wondering what is going to happen when i have my 4 channel amp running. it is a JL 300 watt amp so it should be ok.
i am more than pleased with the controller so far, i will have to see how it does during summer and track days.

You should consider switching to a more efficient fan. The Taurus fan's excessive current draw is well-known, and there are fans out there that work just as well without causing electrical capacity problems.

This is rarely true. When you start a stalled motor at full power, it will draw a HUGE amount of current. 10x (or more) then it's nominal operating current. The result is a lot of heat in the windings and brushes, which significantly reduces motor life. Not to mention the momentary load this places on the electrical system.

The best way to start a motor is using a "soft start" controller which limits the amount of current the motor can draw on startup. It may take a little more time to spin up the motor, but the efficiency is going to be about the same (maybe better, since so much current won't be going into heating the windings) and motor life will be far longer. In addition, the electrical system supplying the current does not have to built up to handle the massive surge.

The exact opposite is true.

Now, if you are referring to controlling motor speed by adjusting voltage, then you are absolutely right. If you lower the voltage of the motor it's going to draw more current in order to do the same amount of work (to a point...remember Ohm's law) and it will burn up the windings.

The proper way to control a DC motor is through PWM, which sends the motor pulses of current. The length of these pulses is long when you want full power, short when you want low power. The motor still sees the same voltage but the available current is limited (though if you measure with a meter that does not handle RMS, you may measure a lower voltage).

AC motors are controlled by varying the frequency of the AC current. Limiting voltage will burn up the windings, and limiting current will result in a weak motor.

Adding a capacitor to the output of the controller will simply filter it's output. The fan will see a steady DC.

They are wired exactly the same. If the wire gauge and fuse is appropriately sized, then there will be no issues.

Figured i would add my 2 cents. Depending on the way you would wire a cap to the system, it could actually do more harm than good. For example, if you were to wire a capacitor directly across the fan input wires then the cap would only be exposed to voltage when the fan kicks on. At that point, the cap will be uncharged because it was connected to the fan and the relay broken the circuit. This will actually be very counter productive. When the relay for the fan does kick on, it now has to deal with the startup current of the fan motor, but it also has to charge the cap that you installed.. The result of this is increased amp draw at turn on and the fan running briefly after the relay cuts the power off. If you were to wire a cap like you do for high current audio amps, it may work, but i doubt you would have any noticable difference. I have to say, putting in a cap is a waist of money, you can buy a 2nd battery for cheaper than a capacitor with high enough farad to make any difference. save your money...