MicroSquirt.com read only forum (Jan.15,2018)

I've been bench testing a MSV3/MSII with the sensors and IAC. I'm running MT2.25 and V2.33 firmware. I've seen some problems with the IAC stepper control but being a MS newbie, wasn't sure I testing correctly. I'm using the 21774 Jeep IAC with the "moving only" algorithm set. During early testing, I found that the S1 connection on the relay board was grounded - fixing this allowed the pintle to move, but not as I would think it should. The 1k resistors are still in place on the MSII.

What I see:
- The Start Value (160) causes the pintle to move outwards whenever the MS is reset, however the IAC position gauge always displays 0 steps. Idle steps haven't been altered default.
- Simulating very cold (-20*) or very hot (210*) coolant temperatures using a pot doesn't cause any movement of the IAC pintle or change the IAC position step gauge. The temps show up correctly on the CLT gauge but don't seem to impact the IAC position.
- Switching the IAC wiring around causes the predicable swapping of inwards or outwards movement of the pintle but only when power is first applied to the MS and there is never any change on the IAC position step gauge.

Is it possible that the UDN2916 chip was damaged by the short on relay board S1 - (1A)JS0 to ground? Have I accidently disabled something in the software? Any better ideas for testing?

Many thanks for your help,
Mike

So one specific question for folks who have this working: Do you see the IAC position gauge change as the car warms up? For example, does the positon step number go down (mine's stuck at zero so I'm not sure what to look for).
Thanks

The inputs for IAC are the initial step command that will cause the motor to move to a stop which can then become the 0 reference position and a table of step positions vs coolant temp. Regardless of whether you even have a stepper chip soldered in or a motor connected, you should see the steps change in MT provided you selected the stepper motor idle option.

Before touching any hardware, reload your processor with the original default settings from the program. Then only change the Idle Control option to be stepper motor and change nothing else. Then turn the coolant pot down to very cold and restart the processor. Then as you gradually turn the pot you should see the steps change on MT. Turn the pot slowly and wait a few seconds between changes of temperature. The reason is that real temperature changes slowly over minutes during warmup and the code is designed to make this smooth without a lot of motor motion based on noise fluctuation in the temperature. So it waits a few seconds between moves. Also as soon as you change the pot it catches the first few degrees of change, moves to this position and then waits a few seconds. By then your pot will have advanced way beyond this and nothing happens. Then all of a sudden you get a big jump in steps. This is by design because you are not turning the pot in a manner that is realistic - you will go nuts if you go that slow.

The main thing is that with the default settings (except you have to turn stepper motor option ON) you should see the steps move in MT without hardware attached. If yo do then you can load your setup and look at what is different and go from there. If you do not see any steps changing in MT with the default code settings, then it means that something is not right in you MT install - probably the ini file is wrong.