Riccardo

iTrader: (1)

This has been discussed many time and all this thread is about is (please correct me if there are any inconsitencies or faults)

a) To give a list of possible fixes (based on my search in the forum)
b) To detail my experience of the fix
C) To have forum members provide an update on how their fix is working

Problem (for those reading such a thread for the first time)

When installing a Power Fc many people (especially with the R models) have experienced problems with the A/C - i.e. A/C will turn on only on a few fan settings - for me it only turned on on fan setting 1, and sometimes on 4). Apparently this is because the Power FC tolerances stricter and there is a voltage drop at the fan switch and wires due to corrosion

a) Possible solutions
- Change Fan Switch (FD0161C50 - USD 92.66)
- Change Engine Harness (expensive c. USD 580)
- Add ground at fan switch
- In series diode
- Yank harness
- ECU bypass

b) Not beeing particularly mechanically gifted I decided to go for th adding an extra ground to the fan switch. This took me the best part of the day as I actually opened the fan switch up and cleaned it - there was quite a bit of dirt but it was not corroded. I added a ground by tapping into the wire coming out of the fan switch.

Result so far (as I will update this in a month to check it is not temporary) is that it works everywhere other than fan setting 3

C) This is up to you guys !

Riccardo

iTrader: (1)

Common guys
How have the various fixes worked for you ?

cewrx7r1

iTrader: (2)

OK!

I wrote up the original ECU bypass to have the AC on all 4 speeds except the engine would not speed up when the A/C came on. So I adjusted the idle up higher for the normal and electrical load settings. That solved the problem.

Then when I totally rebuilt my engine including a new engine harness, I disengaged my previous bypass for testing. Now the A/C is running 100% of the time on speeds 1,2, and 4 and 90% of the time on speed three without the ECU bypass.

HYDOUKEN

iTrader: (1)

Hey Riccardo how is that fix working for you? Is it still working on all fan settings except 3. Also another trick that you didnt mention that I read about actually works for the R1 models is turning the fan switch in the half way position. Basically if you want fan to be at speed 3 just turn the **** to 3.5 and watch the sensor indicator on the PFC commander and when you see that sucker light up....stop. But this is alittle troublesome to do in stop and go traffic so if your fix works that would be much better than having to switch screens on the commander everytime I want to adjust the a/c.

Riccardo

iTrader: (1)

Yes indeed I forgot that fix...
So far so good....3 still never work however

Riccardo

iTrader: (1)

March 1 Update
So far so good
All works other than setting 3

HYDOUKEN

iTrader: (1)

hopefully I will get around to trying this simple mod soon...........summer will be here before I know it. I wonder why fan4 will work but now fan3

Riccardo

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Indeed a good question, that I have no real answer to

gorockrx

Hey guys...I had the same exact problem on my R1 when I first got it.

My fix so far was to bypass the thermistor switch that is located on the evaporater coil behind the glove box. Everytime I press the A/C button...my air gets cold...in any fan position.

The only thing that doesn't always work is the idle speed up, but I have the idle set up a bit to compensate. Also, have to switch the A/C switch off every once in a while so the expansion valve doesn't freeze up, but I have had NO problems in 14k miles...summer and winter...!

I studied the wiring diagrams for a while to come up with the bypass, but in reality it is very easy. Just took a piece of 18ga power wire and put a blade crimp on each end and removed the blade connections on the thermister and installed the jumper and it works great.

Hope that helps someone...
Greg

Riccardo

iTrader: (1)

Very interesting Greg
Can you please detail a bit more for those who are not that good (like me) with diagrams and electronics
Thanks

gorockrx

Hey...sorry for slow response...
Life is pretty crazy right now for me...just accepted a new job and moving me and my family to another state! Whew....too much to do.

I will post what I can. I don't have my manual in front of me, so the names of items may not be correct

I came up with the fix after looking at the shop manual wiring diagram. There are only a few things that can cause the A/C compressor to not turn on, so I just went to each part of the system and checked it by hand with a meter.

In my case, the problem was with the temperature thermistor switch located just behind the glove box. It is simply a 2-wire on/off switch which is designed to keep the expansion valve from freezing up by turning the A/C compressor on and off depending on how cold it senses that the evaporator coil is. It is in series with the A/C ON/OFF switch and the Fan Speed switch and DIRECTLY controlls when the compressor kicks on and off. It might as well be the ON/OFF switch on the dash, cause it does the same thing.

Mine is bad and caused the A/C to only work in fan position 1 and 3, but it didn't always work..came on and off whenever it felt like and drove me crazy. I would guess that there are many rx7's out there that have a bad switch and think it is the Power FC's fault. In my case the switch was bad.

To fix the problem I simply jumpered the connection behind the glove box with a piece of wire and the problem has been gone ever since. The only thing I have to remember to do is to turn the A/C off after it gets cold enough, cause I don't want to freeze up the system. The Air works really well, so I don't leave it on long enough to have a problem.

A new switch would probably solve the issue as well, but Mazda is VERY pround of that switch. I checked with the local dealership and I think it was $286 or some ridiculous amount....so I just decided to bypass it.

Maybe I can take a picture of it and that would be the easiest way to explain. I will try to do that when I get a few minutes of free time...

Hope that helps explain it better. It is the middle of the night, so might not read to clearly...

killer13b

If the problem is with the voltage drop at the fan switch (low voltage), has anyone thought of trying to put an amplifier of some type (usually a transformer of coil) toost the voltage at the switch. Less coils on the input side and more coils on the output side should raise the voltage but it will lower the current flow proportionately. For instance, 5V applied, 100 coils input, 200 coils output, and say the resistance in the circuit llimited the current flow to 1 amp before the amplifier was installed. After this coil is installed the voltage will be 10V and the current flow will be .5 amp on the output side. Remember, current flow is directly related to the amount of resistance in the circuit, no matter what the applied voltage is. I have a 93 R1 that doesn' work on fan speed 3. I put the stock computer back in to test for the problem, and sure enough the A/C worked just like it was brand new. I can't run the stock computer as I had my friend of 20 years Nick VanNugteren, ROTARY RELIAIBILITY and RACING, 2608 South Harbor Boulevard, Santa Ana, California, (714) 839-8018. He was the first to pull 1G in a gen 1 and also held the Bonneville speed record twice in a gen 1, 190 mph +, and 207. He does all my rotary work for me that I don't do myself. He ported my engine, 2mm apex seals. TO4 turbo, big intercooler, bigger injectors. full exhaust, etc., etc.. The problem as I see it, is Apexi needs to either come up with a chip swap or a new program. They're Japanese. That's what they do. They refine things and make them work.

Riccardo

iTrader: (1)

Very interesting post gorockrx - I think it would be very usefull if you could post a picture

killer13b I have been asking myself the same thing, but I do not have the technical expertise to do so

silver-rex-7

I'm burning up in my car. I put the power fc on and the ac and the climate control was working. I went away for two weeks and when I came back my whole climate control and ac didnt work. I went to the function switch check screen on the power fc commander and when I pressed the ac button on, on any fan setting the ac engaged. I can hear the engine slow down a little bit. The last setting I had on the car before I left was on winshield defrost venting setting, and on hot. I seems it got stuck that way does anybody know what the hell is the problem. I just read this whole thread and I just need a direct answer before I start tearing my car appart just to fix the ac. I dont care If my ac works or not I at least need outside air to blow from the vents or something to cool me off once in a while.....

Riccardo

iTrader: (1)

Since you say the Power FC shows that the AC turns on, I think it is unrelated to the PowerFC
I suggest you post on the 3rd Gen forum to get some help

killer13b

My friend Nick at Rotary Reliability and Racing/Fast Freddy's is working on an A/C fix that bypasses the Power F/C a vacuum controlled pressure switch. When it comes together I will post the results of the fix.

Riccardo

iTrader: (1)

Yes please do !

Riccardo

iTrader: (1)

Fix still working...

killer13b

I have a 93 R1 which was experiencing the a/c power f/c thing, working intermittently and never working on speed 3, which is now working on all 3 speeds. If you want to know what I did call 318-325=6150 and we will discuss your problem.

killer13b

killer13b

I'm sorry, I made a mistake earlier. It works on all 4 speeds

killer13b

Riccardo

iTrader: (1)

This is the A/C "wire" fix courtesy of CEWRX7R1, I think he latter added a pressure sensitive vacuum switch at 2psi
[...]
I claim no responsibility or liability for anyone who follows my instructions.
You are solely responsible for any changes you make to your car. Do not attemp
this if you are not experienced with wiring.

Following is details from the manuals and how to make your AC work with the PFC.
Three ECU AC functions will be lost with this conversion. If the AC is on, it will not be temporarily disengaged when starting the engine. When accelerating hard, the AC will not be temporarily disengaged. The idle speed will not increase when the compressor comes on. The AC will function normally with all AC components working, except with no ECU control.

Reference materials:
Mazda RX-7 1993 Body Electrical Manual (BEM)
Mazda 1993 RX-7 Work Shop Manual (WSM)

BEM page G-12 AC wiring schematic:
At the left side it shows the AC compressor wiring; +12V - ignition/acc switch - AC fuse - AC relay - AC pressure switch - AC magnetic clutch - ground. From the relay control coil is a Y/B (yellow with black strip) wire that goes to the ECU. It is marked as connecting point 37 and continues on the WSM B-1d schematic. On WSM B-1d, point 37 goes to ECU connector 1L. The ECU basically grounds out this connection to energize the AC relay to turn it on.

In the middle of BEM page G-12 it shows the AC control wiring; Ground - fan speed switch - AC switch - AC thermal (anti freeze) switch - and a wire colored V (violet) going to the ECU. It is marked as connecting point 36. On WSM B-1d, point 36 goes to ECU connector 1E. The ECU basically senses ground through this wire when you turn on the AC.

Cut the two wires at ECU terminals 1L(Y/B wire) and 1E(V wire). This is the bottom connector with 11 pin columns. 1L is the center pin opposite the connector lock tap. 1E is third from one end. Connect the harness side of them together thus bypassing the ECU. Leave the ECU side open. I placed snap-in connectors on all four wire ends so that they could be easily reconnected back to stock.
[...]

coolingmist

I hooked a relay to my car gave it ignition and battery power. I send a ground signal to the 85 pin of the relay when the ac button lights up. I hooked the 87 pin of the relay to the ac compressor wire. but placed a boost pressure switch in line and wired it to the normally closed circuit.

When I hit a specified amount of boost if the ac is running it shuts off. Otherwise if the ac button is pressed and the **** is turned the ac turns on.

Riccardo

iTrader: (1)

Coolingmist
Can you be a bit more precisse

coolingmist

A relay is designed to draw power from the battery, but to make sure the car has to be turned to the ignition before any device can be activated. The 30 pin of a relay is the battery input. The 86 pin is the ignition input. The relay has another pin noted as the 85 pin. the 85 pin is required as input to activate the device. Just use the ac signal (the signal the turns the light on the ac button on). Once that signal goes to the relay it will activate any device that is attached to the 87 pin of the relay.

use the pressure switch in the normally closed position to turn it off at what ever boost range you want. this is so the a/c compressor doesn't get over worked when you are hauling ***.

thanks.

Riccardo

iTrader: (1)

Thanks for the explanatiom
It is very helpful