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The Great A/C FAQ

Old 08-02-2011, 10:35 PM
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Originally Posted by Braineack View Post
its pretty simple.

what's your ECU?


You'd jump 1P to 1S. That will trigger the a/c compressor when the a/c switch is pressed

From 1S, run a diode (banded end towards 1S) to 1I, this will enable the a/c fan.

You don't even need the diode, only if the main fan and cooling fan have been paralleled, this will prevent the a/c fan from activating when the cooling fan comes on.
I have a 2000 miata that I am installing a megasquirt for someone, and (obviously) he has A/C and wants to keep it. Anyway, that does seem fairly simple. Thanks!
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Old 08-02-2011, 10:37 PM
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Originally Posted by Braineack View Post
its pretty simple.

what's your ECU?


You'd jump 1P to 1S. That will trigger the a/c compressor when the a/c switch is pressed

From 1S, run a diode (banded end towards 1S) to 1I, this will enable the a/c fan.

You don't even need the diode, only if the main fan and cooling fan have been paralleled, this will prevent the a/c fan from activating when the cooling fan comes on.
I am installing a Megasquirt on a friend's 2000 NB miata. He wants to keep his A/C, so this most definitely has to go in. The mod seems fairly simple! Thanks!
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Old 08-11-2011, 10:18 PM
  #123  
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Is there an idiots guide for a 1.6 electronics car on MS1 for the AC circuitry? This is my first time doing this and I haven't seen it yet. I had no problem with the IAC settings on my car, it's the wiring I'm worried about.
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Old 08-11-2011, 10:26 PM
  #124  
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yeah, jump 1Q to 1J. the end.
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Old 08-12-2011, 06:28 PM
  #125  
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So long as this thread's been bumped . . . .:

I've pretty much implemented everything discussed here on my MSPNP9093. To wit:

1. Spark Table switching. This is setup to add ~8 of ignition advance when the AC clutch activates. Drawing in my build thread.
2. Purge Valve solenoid mod, including all-important flyback diodes to protect the MSPNP electronics. This is setup to open the purge valve and create an air leak when the AC clutch activates. Drawings (even pictures!) in my build thread.

The mods work. My car would not stall, although I still needed to contend with idle dip when the AC was on.

Last weekend, I did something that had about as much effect as both of the above combined. Some time ago, my car had been converted from R-12 to R-134a. With R-134a, the cooling was OK, but the compressor load was horrendous . . . like a boat anchor. This, of course, makes idle control difficult.

I had been researching alternative refrigerants and stumbled across one called ES-12a. It's hydrocarbon based (essentially, it's butane). However, it advertised that it required less power to compress. So, I gave it a shot. Last weekend, I evacuated the system and charged with ES-12a. Didn't have to do anything else because it is compatible with the R-134a PAG oil. You charge to about the same pressure on the low side, but the high side pressure ends up being MUCH lower than R-134a. I've been driving it all week (in N. Texas, no less). It cools as well as the R-134a, but the compressor load seems to have been cut in half! That means more power all-around and pretty much no idle dip.

Anyway, I'm happy with it. I recommend it from the standpoint of compressor load, but you'll have to decide for yourself if you're comfortable charging your AC with butane.
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Old 08-12-2011, 07:50 PM
  #126  
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Interesting! I was starting to consider looking for a smaller compressor which would give less load on the system. Will do some research into this ES 12a.
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Old 07-01-2012, 07:40 PM
  #127  
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Broken images on page 1.

I need to get my AC working. PO said it worked on his 95 and it does not on my 94. :( I should say that the fans DO run, but the compressor does not kick on. I should also add that i do not care about turning off the AC at WOT, at over 200hp, i'm not really worried about it.
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Old 07-02-2012, 11:34 AM
  #128  
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you have an MSI on a 94 and your a/c fan turns on but not the compressor?
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Old 07-02-2012, 12:27 PM
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Originally Posted by Braineack View Post
you have an MSI on a 94 and your a/c fan turns on but not the compressor?
MSII i thought, with a microsquirt board. No idea who even built it, but i've already had to change / add a couple things.

The one fan comes on when it should and they both turn on with the AC button. But no compressor.
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Old 07-02-2012, 12:30 PM
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You'll need to pop it back open and doouble check that input 1 or 2 (whichever is being used for the a/c relay) is going from 1Q to input IN, then input OUT goes back to both 1J AND 4S. sounds like it's only going back to 4S right now.
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Old 07-02-2012, 03:30 PM
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Originally Posted by Braineack View Post
You'll need to pop it back open and doouble check that input 1 or 2 (whichever is being used for the a/c relay) is going from 1Q to input IN, then input OUT goes back to both 1J AND 4S. sounds like it's only going back to 4S right now.
Hmm. I have a cut wire in INJ2 No idea where it went. and 1J goes to 1Q. So should this INJ2 should go to 1J? Then 1J goes to 4S.

Last edited by Erat; 07-02-2012 at 03:41 PM.
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Old 07-02-2012, 03:52 PM
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hahah. okay dude. think about what you just said for a second.

you just asked if INJ2, injector output #2, should connect to 1J (a/c relay). Simmer down, if you do silly things, they can have horrible consequences.

I have no idea why you have a cut INJ2 wire. if you the car runs on all 4, don't worry about it.

1J to 1Q is correct. 1Q is the a/c switch input and 1J is the a/c relay trigger. When you switch on the a/c (1q), it grounds the a/c relay (1j) and powers the compressor.

4S is the a/c fan. That can only be activated in the same manner. I'm uncertain as to how, if 4S isn't wired up to 1Q, the a/c fan could ever run. But it's possible the early 94s are like the 1.6L where there's only one relay.

Please double check this. If 1J is connected to 1Q and the compressor isn't running you either have low refriderant, a bad thermoswitch on the evaporator box, or a bad compressor.
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Old 07-02-2012, 04:07 PM
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I don't know if i'm thinking way to much into this or i'm missing something. 1Q is connected to 1J, right next to each other which i'm assuming is both IN. Then the smaller 1J down below, which i'm assuming is out, is connected to the smaller 4s OUT.

So i'm guessing it's right. It's a hardware issue.
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Old 07-02-2012, 04:08 PM
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stop assuming.


1J is connected to 1J?


come on. i told you exactly what to do.



can you take pics of the board, both sides, where everything connects up?
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Old 07-02-2012, 04:09 PM
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Sorry, i mistyped.
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Old 07-02-2012, 04:13 PM
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if 1J and 1Q are simply tied together, then you have an issue with your pressure switch (low coolant?), thermoswitch, or compressor itself.
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Old 07-02-2012, 04:20 PM
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It's wired on both sides.
Attached Thumbnails The Great A/C FAQ-dsc04402.jpg   The Great A/C FAQ-dsc04403.jpg  
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Old 07-02-2012, 04:26 PM
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I built the unit, someone else modded it.

the green and yellow wires arent mine.


can you please picture where the green and yellow wires go and get cut off? they made a mess of it.
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Old 07-02-2012, 04:32 PM
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Hmm, so it's hacked up. This might also explain why my EBC does not work.

Want to just build me an MS3?
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Old 07-02-2012, 04:40 PM
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like one green wire is going to 4X, that the purge valve... unsure what that's used for (would need to see where it's going and your MSQ)

EDIT: okay, EBC output is going to your purge valve...probably for easy wiring.

there's a green wire going to 1L, where I again dont see where it's going to. that's your main fain...that should have been a red wire connecting to CLT on the top of the baord, but that was obviously moved and replaced.

EDIT: cant see where this is going without looking at a board for reference. need to see msq.

1V it input IN is the clutch switch, that shoudl go back to FLEX or something, but i cant tell. I didn't add that.

EDIT: correctly wired for launch control.

the wire to 1E is your CEL, so I guess they were trying to use it to light up for some reason? would need to see MSQ to see why, and where it runs.

EDIT: cant see where this is going without looking at a board for reference. need to see msq.

what's the little metal jumper on the connectorboard aboe 1L and 1J...that looks odd, can you get a close up?







but as wired, the a/c should work. looks like 1Q, 1J, and 4S all tie together, which is fine.
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