So i have been doing alot of reading and research on having manual fan control and have settled on a circuit board to control the duty cycle (ground side) to the fan. What i can't seem to find is the frequency of which the computer controls it from a low fan speed to max. Anyone have an idea?

 

Proprietary information. Not publicly disclosed.

 

This isn't NASA stuff!
Anyone with an oscilloscope can see it.

 

Yeah, this is going to be hard to get. Maybe we need Yahiko to get out the oscilloscope and get us some readings so we can design a circuit board which can take over control but not back feed the PCM. Sure would be super slick to have something like this.

 

Show of hands how many people own an ocilloscope?
Fan speed is PCM controlled from serveral sensors not any one sensor.
However if you want to manually control it you would have to pick certain on/off points your self and hope they are good enough.

PCM defuelas at 250 deg. OT so that is a max point but other things are happening with the oil at those temps as well so you want it to come on well before that. After that is up to you[and all on you] and how good of choices you made.

Not saying it can't be done, just should it be done.

 

The problem i've got (not yet this year) is when i'm in the city pulling a trailer on hot days my temps get up to 220 plus or minus a few. Basically i want some manual control from the fan especially with stop and go traffic. I know some people have supplied ground to the control side on a switch but i dont want it to be going full speed. To be able to supply 10, 30, 50% whatever to the fan would be nice. I don't like my temps getting way up there and simply turning on the a/c to turn it on sooner is not enough. If i can find the frequency to get the appropriate controller then this would be a hell of a good mod. Unfortunately i dont have access to an oscilloscope.

 

Have you already watched your fan speed during these times of towing in the city?

I would bet your fan speed is already running 10-30-50% at different times during these trips.

 

While I neither endorse this nor condem it.
You can use data logging with an extended log or 2 to under the same general conditions your going to operate at.

Observeing fan operations you can establish a baseline under normal conditions and then make a more informed desicion.

 

I own one. They are not that expensive. You can command the fan duty cycle using a scan tool. Toss a scope on it and I don't see anything terrible difficult.

 

This is why factory gauges are "dummy" gauges. Running at 220 degrees is not a problem.

 

I built my dual trace ocilloscope in 1968 as my final lab before graduateing in 69 with an electronics degree. I have used it almost continuosly since then. I still considerr my self a novice with its use.
How much have you used yours. I bet you did not learn it overnight??
Asking an unexperienced user to use a ocilloscope is asking an awfull lot don't ya think.

 

I don't have much experience with it, but I would wager that give me 30 minutes and I would have it figured out.

I don't think it is asking much. All you are measuring is the duty cycle of the fan control.

 

Before I went through all that trouble I would put a set of fans up front with a separate switch. It might work out cheaper in the long run and keep the A/C frosty in stop and go traffic.........just food for thought

 

Lets not forget that PWM is the on time in relationship to the off time







Was going to let this slid by but someone might understand what they are seeing. The display on the scope is from the
Hall Effect speed sensor. I did not take any photos of the PWM signal but it was nearly the same. The big change was the voltage.



This thing is the breakout box to get at the signals from the PCM to the fan.

One handy tool for working with PWW would be the arduino circuit board. You program with you computer to output
a PWM and use a transistor type device to handle the current that will be needed to run the fan at a predetermined input
to the arduino. I hade even started to work on a project for this reason but set it off to the side during back surgery and
never got back to it.

The transistor you are going to need will have to be able to sink a few amps of current.

For the ones that don't under stand sink and sourse have a look here.
npn - Sinking and sourcing current - Electrical Engineering Stack Exchange


Sean

 

Way over my head,I like the KISS method better