Stepper IAC wiring - pin 29 missing

Ask questions about DIY board assembly issues, fault finding and testing. (Covers all Megasquirt versions and board.)

Moderators: jsmcortina, muythaibxr

Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Stepper IAC wiring - pin 29 missing

Post by Madkaw »

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
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
billr
Super MS/Extra'er
Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Stepper IAC wiring - pin 29 missing

Post by billr »

Use pin 36 that was reserved for the single-coil ignition driver.
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

Okay - I will look at that. Will I set up in the tuner studi differently ?
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
billr
Super MS/Extra'er
Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Stepper IAC wiring - pin 29 missing

Post by billr »

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.
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

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
Attachments
RenderedContent-7726B7DF-53A5-4519-8498-3EB02E8BEB7E.JPG
RenderedContent-7726B7DF-53A5-4519-8498-3EB02E8BEB7E.JPG (115.5 KiB) Viewed 1053 times
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
Six_Shooter
Super MS/Extra'er
Posts: 1420
Joined: Mon Oct 17, 2011 7:28 pm
Location: South Western Ontario

Re: Stepper IAC wiring - pin 29 missing

Post by Six_Shooter »

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.
Tha Toy: 1973 Datsun 240Z Turbocharged, and loads of fun, now MS'd
Tha Otha Toy: 1923 T-bucket Hot Rod, Currently Sniper'd
Tha Daily: 2005 Chevy Blazer
Tha Summer Daily: 1987 Buick Skyhawk hatchback
Tha Long Term Project: 1985 GMC S-10 Jimmy, hasn't been fun for a while
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

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
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

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
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
billr
Super MS/Extra'er
Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Stepper IAC wiring - pin 29 missing

Post by billr »

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"
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

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
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
billr
Super MS/Extra'er
Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Stepper IAC wiring - pin 29 missing

Post by billr »

"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.
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

My apologies - I need to proof read my posts.

1&4 read same ohms as 2&3 - approx 50
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
billr
Super MS/Extra'er
Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Stepper IAC wiring - pin 29 missing

Post by billr »

Alas, I am not able to see much of the board in that photo. I can pan vertically, but not horizontally.
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

I would be happy to shoot more pics . Can I ask specifically to what we want to see?
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
jsmcortina
Site Admin
Posts: 39587
Joined: Mon May 03, 2004 1:34 am
Location: Birmingham, UK
Contact:

Re: Stepper IAC wiring - pin 29 missing

Post by jsmcortina »

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 can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
billr
Super MS/Extra'er
Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Stepper IAC wiring - pin 29 missing

Post by billr »

I tried both, no joy.
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

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.
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
billr
Super MS/Extra'er
Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Stepper IAC wiring - pin 29 missing

Post by billr »

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?
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

I think I get it- will check it out when I get home - thank you . I’ll owe someone a Starbucks for sure
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
Madkaw
Experienced MS/Extra'er
Posts: 368
Joined: Wed Mar 05, 2014 3:33 pm
Location: Bloomington Indiana

Re: Stepper IAC wiring - pin 29 missing

Post by Madkaw »

Okay-test accomplished. Looks like it failed by your numbers.
1a -0v
1b-12v
2b-12v
pin 36-12v
Steve
1971 Datsun 240z 3.2 L6 1975 EFI intake plenum 60mmTB with 42lb Bosch injectors
MS3x 3.57 Ignition LS1 coils running full sequential
!983 Nissan 720 MS2/3.57 ported efi 26lb Bosch VW 4 tower ignition wasted spark
Post Reply