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Best output to use for fans with MS2

Old 05-20-2010, 01:24 PM
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Default Best output to use for fans with MS2

So I just relized i cannot use JS0 as a fan output, and since I use Fidle for idle control, and we use the 2 outside LEDs for ign. and the middle for warmup, what the heck can I use for a fan relay output?
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Old 05-20-2010, 01:35 PM
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What exactly are you using the middle (warmup) LED for that's so important? That's where I'm driving my fan from.

Just replace the 2N3904 that's normally there with a 2N2222, remove the LED and the series resistor, and wire the relay to there.
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Old 05-20-2010, 02:44 PM
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So I remove the LED, Remove R27, then connect the transistor B pin to a 1k ohm resistor, then connect that to R27, pin closest to the heat sink, correct?

Do I need to remove Q7???


also, can I get the 12V to run through the 1N4001 diode form the left side of D9, or do I have to connect it to the 12V at the relay, like in this guide??

http://www.megamanual.com/ms2/spare.htm

Last edited by cardriverx; 05-20-2010 at 02:54 PM.
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Old 05-20-2010, 04:08 PM
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You're running a 3.0 PCA, right?

If you want to keep things really simple, remove Q7 and D15. (R25 can stay, or it can go. Doesn't matter.)

Also, leave R27 in place.

Replace Q7 with a 2N2222. The only difference between these two parts is that the 2N2222 is rated for a higher collector current: 1A vs. 200ma. The 3904 might work (I have no idea what the coil current is on a stock fan relay) but why chance it?

Ok, having replaced Q7 and removed D15, you'll want to run a wire from the hole in the board where D15 used to be out to whichever pin on the DB37 you want to connect the fan relay to. Which of the two holes? Whichever one has continuity to the bottom pin of Q7. I think this will be the upper (square) hole of D15, but I don't have one here in front of me to look at right now.

So basically, you're going to end up with this:


Last edited by Joe Perez; 05-20-2010 at 05:07 PM. Reason: R27, not R17...
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Old 05-20-2010, 05:04 PM
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i use one of the IAC outputs to drive my fan relay. never had a problem with it, works fine.
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Old 05-20-2010, 06:49 PM
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um, why cant you use JS0? What other thing is using it that you cant?

on my MSII, JS0 runs my fans just fine
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Old 05-20-2010, 08:04 PM
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Joe, it works perfect, thanks.


marc, there is no option to use js0 as an output, how did you?
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Old 05-20-2010, 09:46 PM
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JS0 will probably be labeled as IAC1
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Old 05-20-2010, 11:31 PM
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Originally Posted by Braineack View Post
JS0 will probably be labeled as IAC1
^^^ This.

I dont know why they wont label these like that, they always have to have some stupid label.

PT6 = JS0 = IAC1
PT7 = JS2 = IAC2

Last edited by Marc D; 05-21-2010 at 07:59 PM. Reason: stupid typo
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Old 05-21-2010, 01:56 AM
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Originally Posted by Marc D View Post
^^^ This.

I dont know why they wont label these like that, they always have to have some stupid label.

PT6 = JS0 = IAC1
PT6 = JS2 = IAC2
Well now I know haha. Why cant they keep the name consistent? Is there a table of all the JS pins and their other names?
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Old 05-21-2010, 02:03 AM
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Originally Posted by cardriverx View Post
Well now I know haha. Why cant they keep the name consistent? Is there a table of all the JS pins and their other names?
As far as ive looked, nope.

http://www.msextra.com/doc/ms2extra/...htm#ms2options

This is a chart for the MSII, but NOTHING states on what's IAC1, IAC2 or WTF PT6 or PT7 is.


But good thing you know. This should be added to the MS FAQs, seriously. I'd rather have the information readily available for people rather than having to experiment.
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Old 05-21-2010, 02:09 AM
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I will put everything I have learned about the MS2 on the miataturbo.wikidot.com site.

Originally Posted by Marc D View Post
As far as ive looked, nope.

http://www.msextra.com/doc/ms2extra/...htm#ms2options

This is a chart for the MSII, but NOTHING states on what's IAC1, IAC2 or WTF PT6 or PT7 is.


But good thing you know. This should be added to the MS FAQs, seriously. I'd rather have the information readily available for people rather than having to experiment.
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Old 05-21-2010, 11:42 AM
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Here's some info on spare ports and what pins they're on.

http://www.megamanual.com/ms2/spare.htm

EDIT: Which I now realize has already been posted here.

Last edited by ScottFW; 05-21-2010 at 12:10 PM.
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Old 05-21-2010, 11:50 AM
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Originally Posted by Marc D View Post
PT6 = JS0 = IAC1
PT7 = JS2 = IAC2
Edited your typo.

I agree that the way ports are names can be confusing.
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Old 05-21-2010, 01:48 PM
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Yeah, this seems to be one of the side-effects of open source development. As a rule, engineers and computer scientists are pretty bad at documenting things in a way that is meaningful to anybody except themselves, if even that.

For many signals, there are at least three different names.

Pin 38 of the CPU, for instance. In some places, it's called PT6 (PTA6) which is the official designation for that pin in the Motorola documentation. On the rev 2 board, it connected to a pad called X2, and then on the 3.0 board, it connects to a pad called JS0.

Or Output 4. In both MegaTune and TunerStudio, it's called "LED18". Except that there is no LED 18. At least, not on the 3.0 board. On the Rev 2 board, the warmup LED was labeled D18, but for 3.0, they changed its reference designator to D15. The circuit didn't change, only the name.

Then, to make matters worse, some of the pins of the DB-37 have specific names assigned to them, despite the fact that they don't actually connect to anything on the stock board. Pins 25, 27, 29 and 31 are excellent examples of this. They are named IAC1A, 1B, 2A and 2B, however inside the unit, they're just open pads. For the vast majority of us who are not using stepper-motor IAC valves, these conventions are meaningless and confusing, and doubly so since the one idle pin that actually does go somewhere on the artwork isn't any of these four (pin 30, IDL.)


Unfortunately, you just gotta know some of this stuff. Having copies of the schematics for the various revs on hand helps.
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