90-96 A/C blower switch wiring: Joe Perez
 

I got an A/C blower switch out of a early 90's Miata in the junkyard for a random project car I have because I liked the integrated AC button and illumination. Of course I can't figure out some wiring.

Questions:
1)There's a Blu/orange wire that appears to only be grounded out on the top three speeds--Med, H2, H1--but all the diagrams just say "from ECU"..........What exactly specifically is this blu/orange wire for?

2)The AC button switch provides a path to ground for a Blue wire and Green/red wire. Joe states in another thread that the Blue wire is simply "delivers power to the bulb which illuminates when the A/C switch is engaged". The grn/red wire is part of the temperature switch circuit. It looks like both of these only work when the fan is on LOW speed; they have no continuity when in any other speed when looking at the diagram and also with my multimeter.
But that would mean the AC only works in low fan speed. What am I getting wrong?

https://cimg2.ibsrv.net/gimg/www.mia...17ddf54672.jpg


I found three threads with different wiring diagrams:

http://uploads.tapatalk-cdn.com/2016...fc03c98c55.png
https://www.miataturbo.net/general-m...12v-gnd-69337/
https://forum.miata.net/vb/showthread.php?t=665097

The blue wire has continuity to ground but it's going across the fan resistor network. If you're using an auto-ranging multimeter for continuity, kick it into manual mode.

as for the blu orange.. i can't find it in the diagram. Just a reminder, though, that most mazda diagrams are laid out such that power is at the top, ground is at the bottom.

oh hey there it is, bottom left corner. So the ECU is running a pullup that gets pulled down to say "hey turn on the ac clutch" - which it does on (24) - 23 is the input, 24 is the output to the clutch. This allows the ECU to know to idleup, and turn off the clutch at WOT.

edit edit edit: if i edit this enough times, it might actually sound like i know what i'm talking about. (22) is the output. 24 is an input too, iirc to make sure the evap core doesn't freeze. if either (23) or (24) aren't low, 24 turns off.

for clarity - if you're just probing the hvac without the blower motor, i can see how you'd be confused.

https://cimg9.ibsrv.net/gimg/www.mia...7bd818f1a6.png

Actually I'm just probing the blower switch, that's all I'm working with.

I'm going to reread what you said enough times until I understand it lol

With that being said I REALLY appreciate you taking the time with an informed response. Thanks goof. :D

Since I made so many edits, let me re-simplify it with a single example. With the switch on H2, current goes thru the blower resistor (that's on the blower motor) that links up to LO.


https://cimg0.ibsrv.net/gimg/www.mia...53ea435aec.png

So may I make a claim?

Claim: Without the factory miata "resistor assembly", this switch may not work as intended?

Because it sounds/looks to me like your illustrations suggest: With the switch on H2, the current path(red line you drew) goes from that "LO intersection" back through the resistors on a L/Y wire, then onto the L/R wire , through the switch and onto the L/O wire, and into the ecu...

Correct?

Bingo.

That said - most vehicle blower fans operate similarly - with a resistor network (at least until you get to mid 2000's or 90's luxury cars, when they started putting more electronics in the mix).

I just tested it with my multimeter. I wire nutted the four-speed-wires(L/Y-G-R-W) together. Then ran the negative lead of the multimeter to the big black wire(ground), and the positive lead to the G/R wire that yould normally be connected to the thermo switches circuit.
I got a proper reading taking the diodes into consideration.


I like this switch and want it to work, so I think I'll just rewire my trucks blower motor circuits(again...) to work with this switch. If I can't find another Miata blower resistor assy, I can probably use any 4-speed resistor assy in the junkyard(which will have three resistors). Or I can just wire up the original 3-speed(2 resistors) and still use the Miata blower switch.


Thanks for the help goof!

I just found this thread by searching, and since it's not that old, figured I'd ask here.

My car no longer has AC, but still has the button. I'd like to use the AC push button for my EBC solenoid toggle. Is this possible? Looking at that wiring diagram I'm not sure, as it looks like that button only works when the blower is on.

Edit: According to this thread it probably isn't going to work, unless the blower is on. https://www.miataturbo.net/general-miata-chat-9/wiring-gurus-c-switch-wiring-12v-gnd-69337/

I wonder if I can use the cruise control button 🤔