IAC
This is a 3-pole solenoid. I did some measurements to it:
Resistance between pins: (1)- 20ohms -(2)- 20ohms -(3) (So there are 40 ohms between pin 1 and 3)
Without connection it's opening can be changed by rotating or shaking the solenoid. (Guess there's no "default" position)
I can close the valve by applying GND to pin1, and +12V DC to pin2 OR pin3.
I can open the valve by reverse voltage. (+12V DC to pin1 and GND to pin2 or pin3)
There's no movement when I apply voltage between pin2 and pin3 in any direction.
Motronic's idle-setting voltage on pins was +2V, +8V, +9V with DC measurements and ~twice higher at AC with a cheap DVM (guess these are pwm signals so those above are far not accurate values).
NOTE ! "Original" wiring ('0 280 140 509' valve (from E30 -89) is as follows...
Pin 2 -> 12V supply.
pin 1 -> to Motronic ECU pin 22 (white-green)
Pin 3 -> to Motronic ECU pin 4 (white-yellow)
wiring might be same with the '524' valve ?
I have the stock idle air solenoid:
But system has an EVAP purge canister valve (said 'auxiliary air control' earlier):
I'm not sure whether this is part of current motronic config or it comes from some jetronic system. Harness is connected however.
options
- leave it out and block its connection from throttle body.
- or you can control it from GenBoard. A purge canister can trap significant amount of gases (useful in the engine, unwanted in the athmosphere unburnt) escaped from the tank on a hot summer day (such as today).
- resistance is 46 ohms. This might be a useful idea, but has low priority at the moment :)
- actually I used the drill in throttle body for [IAT]
![[IAT]](http://quasar.dynaweb.hu/~lezsi/bmw/conversion/iat.jpg){kind=link}