Air Conditioning subpage of GenBoard/UnderDevelopment/FirmWare

GenBoard/VerThree firmware

Things below are mostly outside the scope of ECU - they are controlled by simple sensors (widely available in the AC industry) and relays.

Air Conditioning clutch output:

Clutch active when signal +12V. appr 450mA (26 Ohm)

Air Conditioning clutch output activation rules

Main fan activation rule

Note that the main fan usually draws 30..40A - almost always a relay is used and a 50A fuse.

The main fan is the 2nd biggest current eater (after the starter motor).

Input signals

AC system pressure signal

Naturally, a single pressure sensor can be used instead of the above range switches (eg. an MPX700A).

Other signals

Misc stuff

These might surprise the unaware, when debugging an AC system:

Some systems are certainly different to some degree.

Automatic AC systems have somewhat more parts, eg.

Vasilis' suggestion

i think i have a solution for a very stable idle control for the audi

engines that can have a good solution for the A/C function as well,

and can make it work with the IAC valve+diode

Here is what is needed:

Under idle settings, put a dialog, IF A/C turns ON, then decreace Idle

PW by X number.

If you cannot control the AC function through VEMS, ( i mean when it

comes ON or OFF) then you can actually do this by using battery


SO if Vbatt = 13.00 then IAC PW decrease by X number

so you can make a simple table of 5 values (i dont think more are

needed) so that the IAC PW can change depending on Vbatt.

This can work in combination to the IAC PW/ CLT.

So for example when CLT=80 and IAC PW=20 if vBatt=14.00

BUT if CLT=80 and vBatt = 13.40 (just when the fan kicks in) then IAC

PW=18 etc.

That way you can possibly eliminate the problem with idle drop AND use the IAC succesfully.

We '''actually do that since 1.1.4x : apply higher IAC PWM duty with lower VBATT voltage. (It's done automatically, unconfigurable atm).