MoTeC Global Forum

Hi
I’m trying to figure out how to set up the M84 to run 2 radiator fans, 1 for engine temp only and the other for engine temp / aircon inputs.
I can work out the radiator fan setup (#102), but the aircon fan setup (#103) doesn’t seem to have a trigger for when the aircon is selected on / off. ??

Looking in the dig in / sw in menu, there’s a ‘aircon request’ (# 5) function
Is this where I send the on/off signal from the aircon switch ??
How do I set it up, it talks about 2v and 3v ??

This is my first time installing an ECU of any sort, more of a points and jet man……

Clayton

Normally the aircon fan will come on automatically when the aircon is turned on.

Switch to aircon bits n bobs to ecu. The ecu then requests the fan turns on and usually the clutch on the compressor

bits n bobs = pressure switches to ensure the pump isnt de-clutched with no gas in the system

Not 100% sure if all systems use the ecu to energise the clutch or if it is a feature of the car.

The ECU has to operate the A/C clutch. Request is the request signal from the A/C system, if all parameters are met, ECU turns on A/C clutch, and A/C fan. So you need two outputs, and one switch input available.

Thanks Guys
A bit more info, I'm building the car from scratch, so there's no wiring loom at all.
At this stage the A/C circuit will be : +12v - Fan switch - A/C switch - thermostat - Binary pressure switch - clutch relay - Motec (clutch cut out at WOT + RPM cut out). So all parameters must be meet to turn the clutch relay on.

I understand I need two outputs, one to each fan relay and have them labeled as 'thermo fan' & 'aircon fan'
Plus one output for the clutch relay, but I'm a bit lost how I set up the aircon request input and does that turn the 'aircon fan' on ??
Is it set up as a digital input and how is it setup ??

Clayton

A 10 k Ohm resister from 12V to a switch to ground.
On the top of the switch that wire goes to the ECU.
That wire should show 12v when the switch is open and 0V when the switch is closed.

If you do not have a 10k Ohm resister use a 20k or 50k.

Most systems the A/C control unit in the dash has a wire into the ECU, when you turn the A/C on it goes to ground, this A/C req line would normally go into a switch input.

Holmz wrote:A 10 k Ohm resister from 12V to a switch to ground.
On the top of the switch that wire goes to the ECU.
That wire should show 12v when the switch is open and 0V when the switch is closed.

If you do not have a 10k Ohm resister use a 20k or 50k.

Thanks Holmz
But you've just past my level of understanding, I'm not sure what you are talking about

Scott@FP wrote:Most systems the A/C control unit in the dash has a wire into the ECU, when you turn the A/C on it goes to ground, this A/C req line would normally go into a switch input.

Thanks Scott
So the 'switch input' in the M84 is located in the 'Digital input functions' ??
To set up an input would I
1 - go to digital input functions
2 - select 'sw in 1 (AT1)'
3 - select #5 (A/C request)
4 - setup parameters - switch closed (LO) or switch open (HI). If I'm using 12v signal to turn on, which setting to use, LO or HI ??
5 - 'Setup' - LO level 2v, HI level 3v ??? I don't understand.

I've read a lot of info on the Motec web site, but I cant find any to help with this.

Clayton

otto69 wrote:To set up an input would I
1 - go to digital input functions
2 - select 'sw in 1 (AT1)'
3 - select #5 (A/C request)
4 - setup parameters - switch closed (LO) or switch open (HI). If I'm using 12v signal to turn on, which setting to use, LO or HI ??
5 - 'Setup' - LO level 2v, HI level 3v ??? I don't understand.

I've read a lot of info on the Motec web site, but I cant find any to help with this.

Clayton

For 12v signal when A/C is on, you would select HI, the levels determine when the switch status goes from OFF to ON. The AT inputs have a 5v pullup on them, so for a HI logic of B+ (battery voltage) the LO level would need to be above 5v, say 6v, and the HI level below what the minimum battery voltage is expected to be, say 9v. So now when the voltage is above 9v the switch status is ON, and below 6v it is OFF.

Also make sure that AT input is not being used by a sensor, usually AT1 and AT2 are used for Engine Temp and Air Temp. For M84 use AT4-6, AT3 is reserved for User 2.

Your a legend Scott
I can understand that, just.......

Now for a dumb question, what is a "User 2"

AT3 is reserved for User 2

So to put this to bed, once I've set up the aircon request the aircon fan will operate via to 2 inputs (engine temp and aircon selected on) or 3 if I use ground speed. ?

Clayton

otto69 wrote:, what is a "User 2"

User 2 is user definable temp input, pin B5. This input has an internal pull-up resistor to 5V, so ntc or ptc coefficient temp sensors are usable.

See: Adjust - Sensor Setup - Input Setup, and Other tab. There you can define a temp sensor calibration, name and behaviour. Usually I use this for Engine Oil Temp (OT), and suitable sensor is eg. Bosch 0281002170.