It's pretty easy so I'm surprised that no one has done this one before.

Tools needed:
Various screw drivers to remove the dash
Soldering Iron/Solder
Electrical tape
2 diodes (I used some that I had lying around, As much as I despise radio shack, they have a good selection of them. You don't need anything special. Just go in and buy some that are rated for at least 12 volts and .5 Amps.)

Basically take apart your dash enough to get the climate control panel out.
Unplug everything so that you can get it out of the car. It's much easier to work that way.

There is a harness on the back of the fan switch. Strip off a short section of insulation from each of the White, Black, and Blue wires. I would stagger where you strip the white wire vs. the black and blue wires so that when you solder the diodes in, everything lays down nicely.

Next, you are going to solder the diodes in. When you look at them, there will be a silver stripe at one end. Take both diodes and solder the ends WITHOUT the stripe to the white wire where you removed the insulation. Now solder the striped end of one of the diodes to the black wire and the other to the blue wire.

Wrap it all up in electrical tape, keeping everything separated by a layer of tape.

Put everything back together and you are ready to roll in comfort.


I attached a portion of page Z-68 from the FSM. The highlighted area is basically what this mod does. (Even though it's location isn't 100% correct.)


I also attached a picture of what the harness should look like minus my crappy solder joints.

 

Are you saying that the PFC will do what the stock ECU does - to cut the A/C off on start up and under high boost? And the A/C indicator on the PFC in the etc. menu goes on? And the A/C works in all fan positions? I guess I would need to take my Y/B wire off my V wire and connect it back up to the PFC.

Thanks for this!

 

Yup, it works just like mazda intended.

 

Sweet! Now I just gotta undo the soldering I just did. Man, this would have been great information to have like a week and a half ago! Thanks just the same.

 

You should put a link to this in your signature.

 

BTW, have you tested it to make sure it will hold up?

 

All it does is provide a ground with less resistance since it doesn't have to pass through the fan resistors, identical to what mazda did with the #2 fan position. The diodes allow your fan speed to still be adjustable. There is no reason that it shouldn't be a permanent fix since it mimics what the PFC sees on fan position 1.

After looking at the attached schematic, one thing that might not be clear is the "L/Y" wire is still continuous under the "L/Y (AC)" label. I forgot to put a connection symbol (round dot) over the connection.

It works GREAT on my car and it should work great on any other car too. I am curious to hear some feedback.

 

Mod did nothing for me. No changes at all.

 

poss, any comment?

 

I now have it working on Fans 1, 2, 3, and only sometimes on 4. with 1 diode from the white wire to the green. according the the wiring diagram that doesn't make any sense. that connects fan 2 to the Electrical Load circuit.

 

maybe it connects to the electrical load circuit to increase idle to compensate for the a/c compressor turning on.
Man I was hoping this would be a simple fix to keep the a/c system, while still retain all the original functions with the stock ecu

 

Explain what you did here:

I didn't write down what the green wire went to so I don't know where it is in the circuit. I assume by what you are saying, it goes to the Orange wire with a blue stripe?

What fan settings did it work on prior to doing this mod? What kind of diodes did you use?

 

The Green wire is the O/L wire on the bottom of the fan switch in the diagram. I started by following your instructions and it did nothing different than before the mod.(working on fan#1 and #2 only) so I decided to play around with the connections. and when I connected thw white wire (L/Y) to the Green wire (O/L) it started working on all four settings. Then fan #4 started only working when it felt like it. But from what I have been reading other post and it seems like on fan setting 3 and 4 (no mod) the A/C light turns off on the commander and the ELD comes on. Well mine always showed the A/C light on all setting and the ELD light on #3 and #4. I don't know if that makes a difference. what it tells me is that the PFC sees it but the problem for me may be elsewhere. any Ideas? has anyone else tried it or just us 2 so far?

 

If the A/C light on the commmander comes on, the ECU *SHOULD* engage the magnetic clutch on the compressor. If it's not engaging, you may be low on refrigerant or have a bad pressure switch among other things, but that doesn't explain why it works on 1, 2 & 3 but not the 4....

 

After thinking about it, connecting the white wire to the green wire is electrically identical to my method. It may even be better since you can acheive the same results with only one diode. Of course maybe you already knew that.

Maybe I should define when to use this mod and when your problem lies elsewhere.
Symptoms:
A/C works on fan speed 1 & 2 (mine used to not work on 2 which makes NO sense, but I'm not gonna question it because it works now)
The A/C light on the commander is lit for fan speed 1 & 2, but not on 3 or 4, or at least not consistently on 3 or 4.

If your A/C doesn't work even on fan speed 1, your problem is elsewhere and wiring it up this way will do nothing.
If the light is consistenly lit on all fan speed settings, yet the air is not cold, this mod will not work, your problem is elsewhere.

 

OK, my A/C works on fan speed 1 & 2 (a/c light on commander is on) but not on fan speeds 3 & 4 (a/c light on commander is off but ELD light is on). Which mod should I attempt?

 

Well I now see how they are Identical. but the new question is why does the 2 diode version not work and the 1 diode version semi-work? also the diodes I am using are 50v 1a from radioshack.

 

You can attach one diode from the white to green wire OR a diode from the white to black and one from white to blue. Really they do the same thing.

(I haven't personally verified that the green wire goes to the O/L wire, but it sounds like xcelir8 knows what he's talking about. )

Keep in mind, the wires I'm referring to are directly hooked to the fan switch, not the ones after the connector. HDP this isn't directed at you, just a general note.

I think all the colors change after the connector so something bad could happen if you don't pay attention.


xcelir8,
The only reason I can come up with for why one worked for you and the other didn't would be coincidence. Really, it makes no sense.

On fan speed 4, the light is lit on the PFC commander right? Is the A/C compressor spinning?

 

The lights on the commander are working perfectly like they are supposed to before and after the mod. but the compressor is turning on and off for some unexplained reason. Is there anything else between the compressor and the ECU that can turn it on or off?

 

a pressure switch...

 

I'm going to do the diod mod. Hope this fixes the AC

 

Give it a try and let us know what happens.

 

The diod fix DOES NOT WORK. Its the switch it self that is bad with age.
I jumpered the switch at the connector to force the AC to work and it worked when jumperd I tried all speeds. Looks like under load the switch has to much resistance. I'm going to buy a new switch. That should fix it.

Alex

 

Holy crap! sorry guys. It worked first try on my car.

Did your A/C originally work on fan speed 1 &2?

 

Yes, I disconnected the switch and made a jumper to test it and it works. The switch must just be old.

Also if you look at the switch diagram it shows a common at fan position 3 and 4.
The drawing refers for (Section B-1b) #28
I don't have that section so if some one does please post it.

Alex