SPAL UNIT QUESTION (MARK 8 FAN)

[AnthonyR23]

So I just received my spal unit today... everything seems like it will hook up great... the spal unit is supposed to have a low and high speed setting.. and my fan has a low and high speed wire... but for some reason the spal unit just has 2 wires that go to the fan red and black.... if I just hook it up to the high speed... will the spal unit still be able to use the low speed setting?? I don't understand why it doesn't have the two speed hookups going to the spal unit??

 

[HISSIN50]

IIRC, the high speed setting uses a relay (triggered by a grey wire). Does that sound right to you? They have some schematics in the instructions showing this stuff but it's been awhile since I looked.

Good luck.

 

[AnthonyR23]

The instructions are pretty good... I have the fan working... but not sure if the high low speed is working... kinda went through the relay that first came with the fan too.. just odd to me that there is three wires coming from the fan and only two that are supposed to go to the fan controler... and one of those two is the ground...

Anyone out there have a mark 8 fan and a spal fan controller?? and does your fan run high and low speeds with this controller?? I just don't have the actual low speed wire going to the fan hooked up... cause I have to at least have the high speed working. thought maybe the controller itself would adjust the high speed down to low speed..

any thoughts??

 

[stang&2Birds]

From *what I remember*, the spal does a a simple two speed "PWM" implementation for the fan. (PWM: Pulse Width Modulation technique.) On high, the fan gets the full "12V". On low, since it's a fan (motor), the need to do a PWM technique.

For an easy example, let's say they do the following:
They put out a 1000 pulses every second. Each pulse is "on" 3/4ths of the time and "off" 1/4th of the time. This results in a fan speed of ~3/4ths (not really, but let's say it does. . This is what you have to do with most electric motors to vary the speed. You can't just reduce the voltage. So, they do a "PWM" (Pulse Width Modulation) technique.

The MKVIII fan, is different. The fan motor has a "center tap" on the coil for the low speed wire. So, if you apply power to just the low speed wire, only half of the motor coil is getting energized. Therefore, it runs slower. That's different than the PWM technique that the DCC fan controller and the ?Spal? fan controller use.

The DCC fan controller is much more intelligent and it varies the pulse width according to the temperature. That way, the engine temp stays more consistent and you also use less power (fewer amps from the alternator, which means less HP needed from the engine to turn the alternator).

Hope the above helps! I've been doing this crud for 7+ years.

 

[AnthonyR23]

great... that explains it!!! We'll I'm happy with it now.. just thought the low speed sounded closer to full then the old low speed I remember hearing.. I am just going to up the low speed setting a bit.. because it seems to be starting the second I start up the car...