GM IAC, Why won't it work?

[3400fierogt]

I've been playing with my gm iac (flange mount, inline plug) for almost a year, and I just can't get it to work. It will not move in or out I tried pushing it in and out manually all the way and midway through it's travel, but it won't move. I pulled it out of the housing and layed it on a board, now when I turn the key on it jumps but the pintle doesn't move. It also gets hot if I have the engine running for awhile.

I have tried:

-swaping the green wires, swaping the blue wires, swaping both sets of wires
-swaping the blue side for the green side, ect.
-the iac was working before my ms install and I tried a second iac.
-the iac has 49ohms between pins 1&2 and 49ohms between pins 3&4
-increasing the time step size upto 6
-testing the power suply to the 40 pin connector

I haven't tried, bypassing the current limiting resistors because I'm not sure if I have my wiring in the right order and I don't want to fry the steper chip.

Any Ideas? even if it's something I've done already, I'm just out of ideas!

Thanks

[3400fierogt]

This is on a ms2 v3, If I bypass the current limiting resistors and have the polarity reversed on the iac will I fry the chip? Or will it only fry if I short it to ground?

Thanks

[3400fierogt]

Someone has to know if the stepper chip will fry when the polarity is reversed, Do the resitors only have to protect it from a dead short to ground?

[S.Bretz]

I know for a fact, it the stock B&G setup, if the polarity is reversed, the chip will be ok.

I had mine all sorts of backwards and it wouldn't move. I flip some wires around and it would move backwards. When it moved backwards, I then switched the greens and blues as per the megamanual says and mine started working.

The megamanual could document the pin locations alot better and state pin locations (A, B, C, D) on the connector, but all yoo get is the picture. With just the picture, it gets confusing and is easy to get things backwards.

Edit: Aslo try increaing the minumum step size up to something high for initally testing (50 steps or so) then set it lower and lower until you get no step movement...use that last know step size where it did move (mine needs to be at least 2-3 steps, so its set to 4 so that I know it will move).

[3400fierogt]

THANK YOU! Thats exactly what I needed to know I'll try it tonight, I think I just peed alittle

[3400fierogt]

I found the problem, I had the iac spareports turned on. You have to turn the IAC ports off when you are using them to drive an IAC. I read the manual a bunch of times and never found this mentioned, It never told me to turn them on I just assumed they had to be turned on so it's my fault but a disclaimer might help someone in the future.

Thanks for the ideas!