I took my car to Ricks Rotary Performance for him to bypass the ECU and so my AC could work. Rick thought it would be better to solve the problem right so he diagnosed the problem. My car is a 1994 with 175K miles. My AC with the power FC initially would not work on setting 3, and would go in and out on settings 2 and 4. After about 1 year it only worked on setting 1. So Rick at www.ricksrotary.com took my car in for service on a saturday. He checked all the electrical connections with the voltmeter and other electrical diagnostic systems. He found the problem to be a voltage drop at the Fan Switch. Keep in mind I can plug the stock ECU in and my AC will work on all 4 settings. Its only with thepower FC that I have the issue. I ordered a new fan switch and sure enough it works on all 4 settings now. Rick spent a good deal of time tracing through the harness, resistors and and all the other components of the a/c system and found all them to be within spec.

It appears that when the switch begins to wear there is a slight voltage drop that still works with the stock ECU, but since the power FC has tighter tolerances it fails.

In my searches on this forum I noticed that 95 pct of you with this problem experience it on setting 3, its possible since setting 3 is the most used fan speed it may wear that contact faster.

In any event a new switch from Mazda solved my problem. I want to thank Rick once again for diagnosing this. I was happy to have him install a pressure switch to the factory ac relay and bypass the ECU, but he wanted to get to the bottom of this not getto rig my car unless there was no other alternative for me to get my AC working.

 

This is excellent information! I recently picked up a PFC and Datalogit and made an appointment for him to install them next week. I'll bring this up when I'm there.

 

Great info! My AC is dead now but it was fan3 that gave me problems after my PFC install, too.

-Max

 

Tell Rick thanks, that sounds like a much more logical solution than just jiggling the harness

Is it the interior switch you are referring to?
What is the part number on the fan switch?

 

Who can get just the fan switch? I just got off the phone with Malloy Mazda and Ray says that they only sell the entire A/C switch set, which is like $500.

 

You can probably clean the contacts of the fan switch with some sand paper and the resistance down to an acceptable level. I've done a similar thing to window switches to bring them back to life.

 

this should deffinately be a sticky! by the way go buy him a six pack or something, he just figured out something that will save a lot of us time, money and headaches!

 

Wasn't this a problem with just the R1's though?

 

Well I decided to do a mini write up on the fix for the switch. It can be viewed on my website.

PowerFC AC Fan Switch Fix

 

This is great news.. nice write up.. but.. ahemm.. what's up with the pics .. so.. fuzzzzy

 

My digital camera just didn't want to take a clean shot. I figured that the shiny not shiny would at least help a little.

Here is a status report from my end. Orginally my AC only worked 1/3 time on setting 1. Now it will work 1/2 time onf settings 1 & 2 and 1/4 time on setting 4. Setting 3 won't work at all. I might get my system tested for correct amount of freon (spelling?) to be sure that isn't an issue. If that doesn't work, then I am going to move the thermoshitch from the input trigger side of the ECU to the output side that triggers the factory AC relay.

 

I too have the EXACT same problem.

No a/c on 3.

works on 1 and 2 ( last I remeber)

Comes in and out on 4.

Hopefully this will fix it for me too.

THANKS!!

 

That's some good info... I too also heard this was a problem mainly for R1's... I myself have a base model '94 and never had a problem w/the a/c... now if I do I'll know how to fix...

 

When I put in my Power FC my A/C COMPLETELY stopped working. It doesn't work on ANY settings. When I put in the stock ecu it works perfect.

 

I think the fan switch is certainly one of the culprits. I suggest using 3M scrub pads (the green or brown ones) to clean the copper oxide off. There is another switch, the thermoswitch behind the glove box that also goes resistive. The combination will drive us all crazy! Wait, too late, I'm already there. I bought an RX-7 .

 

At least you are in Canada!

 

Hey Zerobanger, do you think we can get a part #?

 

$92.66

# FD0161C50


At least that's one parts at Mazda Alhambra says.

 

So when you guys hit the a/c button does it come on but just not blow cold? Basically everything seems like its working but the clutch on the a/c compressor never engages so it just blows hot air?

You know whats unusual is back when I had a/c on my car it ran perfect on all the setting.....I have a 95. I wonder if they changes some parts around for 95 and the PFC design is based on 95 and up.

STEPHEN

 

About your pictures being blurry if you have a digital camera make sure it is in auto focus and if its not an auto focus type make sure you are atleast 4 feet away from object being shot. Photo class. When I do mine I'll take pics and email'em to ya.

later

 

I found this old thread. May as well update. The switch worked beautiful for about a month. After about 30-45 days it quit working on setting 3. Then it quit on 4, then 2 stopped.

I decided to re-wire the a/c compressor and connect to a NO boost switch to detect boost to cut the compressor off. Currently Im using a toggle switch, but some point I plan on using the ac button instead.

BTW..the car blows ICE cold now. Literally ICE cold.

 

I found this old thread. May as well update. The switch worked beautiful for about a month. After about 30-45 days it quit working on setting 3. Then it quit on 4, then 2 stopped.

I decided to re-wire the a/c compressor and connect to a NO boost switch to detect boost to cut the compressor off. Currently Im using a toggle switch, but some point I plan on using the ac button instead.

BTW..the car blows ICE cold now. Literally ICE cold.

 

David,

Can you do a write up on this? I've been wanting to fix my A/C issue for a while now.

Oh yeah, I'll pm you about water injection later.

John

 

Well its quite simple actually.

Parts:

Boost pressure switch.

There are 3 kings. Normally Open, Normally Closed and one that has both NC and NO terminals. You need the one that that is connected until you hit your boost, I think its a normally closed switch. I get these at wholesale prices so if anyone needs one, please PM me.

16 gauge wire
depending on where you mount the pressure switch, probably 10 feet
is enough
Fuse

Vaccuum hose
2-3 feet is enough usually. It depends on where your boost source is.

Vacuum Tee

Electrical tape
Male/Female connectors
zip tie



You want the a/c to get turned off when you hit boost (around 4 psi I'd say).

1)

Take the boost switch at set to whatever PSI you want the ac to turn off. What ever boost switch you buy should have instructions on how to adjust. My switch uses an allen wrench.

2) install the harness. Connect the output or comm connector from the boost switch and connect that to the 12V source to the compressor. run a wire to the power source connector of the boost switch. Take that wire and route it inside your car through the firewall. From here you have several options. The easiest option is to take that wire connect one end to a toggle switch and connect the other end of the toggle switch to the ignition. When you flip the switch the compressor turns on. While this way is easy, you need to make sure that switch is NOT on while the blower switch is not running. I have mine set up this way as I dont have time now to remove my center consol to tie it into the blower motor/ac switch. I also installed a LED that lights up when the a/c compressor is running.

alternative

The boost switch I use can run 15 AMP's so it doesn't need a relay. However if you dont want to use a toggle switch, instead of doing the above, use a relay and do this below.

take the center console apart and tap the the a/c indicator light 12 V wire, connect the other end of that wire to #85 on the relay, 30/51 to the battery, 87 to the ac compressor, 86 will go to the pressure switch and the power source of the pressure switch will be connected to the ignition.

in this case when the ignition is turned and the ac button is pushed AND the blower switch is running and you are not in boost your a/c compressor is running. When you hit boost the compressor will stop running.

All in all takes only a few minutes to install. There are other fixes on the forum. I tried the ecu bypass where they take the a/c wires from the ecu and cut/re-route. That didn't work for my car. This works perfect and again the a/c is really cold. For some reason its colder than stock. I'm guessing that the stock ECU must cylce the a/c on and off regularly.

sorry about the crappy write up. Maybe sometime I'll update my web page with a good write up with pictures. Im just a bit busy now.

 

Thanks for the write up David. I'm sending you a PM. I need a boost switch...