Megasquirt Support Forum (MSEXTRA)

Well I went to check that I had all my jumpers on my 3X and realized I had broke pin 29 a long time ago , so unless there's an alternative way of wiring a 4 wire jeep IAC , I guess I need a new main board connector?
Thanks

Use pin 36 that was reserved for the single-coil ignition driver.

Okay - I will look at that. Will I set up in the tuner studi differently ?

No, I don't think anything non-standard is needed in TS. Just be sure the Q16 output ("IbgtOut" pad) is disconnected from pin 36 ("IGN" pad), if there is a jumper already installed between those two pads.

Thanks so much for the reply. I took a pic of the board since I wasn't sure if your explanation . I am not currently using pin 36 and the board is unaltered 3.57

Any spare output pin can be used. The pins that are in the manual are simply suggestions to keep things easy across many installs. They are simply a way to get the signal from the inside to the outside. The CPU has no idea what physical pin is used at the db37 connector, so, no, no software changes neded.

That's good to know - though it's going to take a while for that to sink in. I'm pretty good for following the MS instructions , but things get fuzzy sometimes for me. My thinking is that the software expects to use those wires for a stepper
But anyway- looks like to me the pin 36 is good to go

Thanks again

Finally got around to trying my stepper IAC . Could not get it to function properly . The unit is a Borg Warner and it did measure 50 ohms at the center leads . Wired per manual and it would hum but not move . The only combination that would make the stepper move actually ran the pintle all the way out and wouldn’t stop with the in and out test. Below is how it was wired with the top numbers representing the motor wires left to right. Is there a voltage test that can be done to check that all wires are working?

1 2 3. 4
1b. 36. 1a. 2b

50 ohms from 2 to 3, and 50 ohms from 1 to 4; and no connection from 2/3 to 1/4 or to ground from any pin? Yes, there are voltage measurements that can be made, but it may get a bit confusing. Let me study how slow you can move that thing in "test mode"

So i checked and ohms are the same on 1&4 and 2&4 . Nothing grounds at the motor . Am i supposed to see if any wires from MS ground , because they dont either .
How slow . I could only get the motor to move in one direction at one speed during test - in and out

"1&4 and 2&4 "

Is there a typo there? That would mean either it is defective or not a 2-coil stepper. Avoid typos when posting here, they cripple attempts to help you.

No, when used as a stepper driver, no wires from the MS are "always grounded". None are "always hot", either.

PS: I have to admit, I hadn't seen the photo of your board before, I'll have to peek at that better later today.

My apologies - I need to proof read my posts.

1&4 read same ohms as 2&3 - approx 50

Alas, I am not able to see much of the board in that photo. I can pan vertically, but not horizontally.

I would be happy to shoot more pics . Can I ask specifically to what we want to see?

billr wrote:Alas, I am not able to see much of the board in that photo. I can pan vertically, but not horizontally.

Try opening the image in a new window or saving, then opening. I think it is a phpBB (forum) issue.

James

I tried both, no joy.

So do I need more pics?
I tried again today with the wiring . I used both examples in the manual. I can get the motor to run in one direction only - it seems. When I limited the steps (160 instead of 255)and tested home the piston does seem to want to go fully closed or out . Any other tests -like in and out -just makes the piston goes further out until it falls out.

I will certainly need a different picture format to try checking the board visually.

We can try to do some measurements with a voltmeter, but it might get confusing; writing isn't my forte...

Set the IAC control "Power Between Steps" to "alway on", if not that way already.

Connect one voltmeter lead to ground, and leave it there.

Use the other meter lead to read voltage at each of the four IAC wires, with the IAC connected and not moving.

At any given time, each coil should have near-zero volts on one wire and battery voltage on the other. That is, 1a=0V & 1b=12v would be a good reading; but so would would 1a=12V & 1b=0V. You want to check all four wires to see if two are low (0) and two are high (12V) whenever the IAC is not moving. Then, use test mode to move the IAC a few steps and read again. Do the move-and-read bit enough times to ensure both coils are getting both "polarity" of drive voltage. This isn't a perfect test, but at least a good first step. If it passes this test, it doesn't mean the coil currents are being changed in a correct pattern, but if it doesn't pass the voltage test above, then something is surely wrong with the drivers/wiring.

Clear as mud?

I think I get it- will check it out when I get home - thank you . I’ll owe someone a Starbucks for sure

Okay-test accomplished. Looks like it failed by your numbers.
1a -0v
1b-12v
2b-12v
pin 36-12v