Need some advice on ac wiring R33

[nicostar]

So I've an r33 sedan 1997, years ago I did an engine swap and the electrician cut one too many wires. I fixed most issues over the years like abs and other running issues that were related to wiring. R33 now runs perfect. I have one problem left and that is the AC, I searched and searched and cannot find an ac button signal from any wire that comes from the ac control unit, neither I see any change to the thermo amp wires when ac button is pressed on and off. I checked the wiring diagram and it shows a pin 27 (grey) from the ac control unit goes to a pin 36 on the ecu, I don't understand this as the only ecu that utilizes pin 36 is the rb26 ecu and that is engine air temp sensor. My engine harness has no wire going to pin 36, and I've checked other engine harnesses for different rbs and none carry the wire for pin 36. 

can someone point me in the right direction for getting the compressor to turn on using the ac button? I've tried hooking up the pink wire from thermo amp to pin 46 on ecu and compressor relay wire (green with red stripe) to the pin 9 on ecu but no response, no changes and no switching signals that corresponds with the ac button. Thanks for taking the time to read, any help will be appreciated.

Edited July 22, 2019 by nicostar

[GTSBoy]

Um.....the Air-Con controller tells the ECU that the AC is on and the ECU does some of the work. Pin 36 is pretty explicitly therefore the signal from the controller to the ECU. Doesn't matter that the ECU doesn't have anything else on that pint. In fact, the ECU does want anything else on that pin.

I don't have any R33 wiring diagrams myself, so I can't look it up for you. But if you have them, then you have what you need to fix this.

[nicostar]

51 minutes ago, GTSBoy said:

Um.....the Air-Con controller tells the ECU that the AC is on and the ECU does some of the work. Pin 36 is pretty explicitly therefore the signal from the controller to the ECU. Doesn't matter that the ECU doesn't have anything else on that pint. In fact, the ECU does want anything else on that pin.

I don't have any R33 wiring diagrams myself, so I can't look it up for you. But if you have them, then you have what you need to fix this.

I have the diagram and hooked up how it says it should, no dice. only thing that is puzzling is the grey wire from ac control, it goes back to body loom and is just a loose wire there. I tried hooking it up to pin 36 and tested the system and still nothing, as I mentioned there are no wires in the harness for pin 36 (from the factory) and every ecu pinout I've seen says it is empty.  

Edited July 22, 2019 by nicostar

[GTSBoy]

Maybe post up some nice big screenshots of the diagram. I can look at R32 & R34 stuff at home, but it won't necessarily match, colour for colour, pin for pin.

[nicostar]

19 hours ago, GTSBoy said:

Maybe post up some nice big screenshots of the diagram. I can look at R32 & R34 stuff at home, but it won't necessarily match, colour for colour, pin for pin.

ok I hope they are clear enough, I scoured through them like liquid plumber in a drain pipe. 

[GTSBoy]

Alright....looking at the 2nd of those images, I see that ECU pin 36 (and apparently ECU pin 31) are connected to the FICD solenoid valve. That's the Fast Idle (Control Valve, I guess). Used for idle up. So when the Air-con sends a signal out on that same connection, the idle speed will increase. Easy enough. What I can't easily read from the AC controller end of that grey wire is which pin it is connected to. But it's definitely not pin 27, because I see pin 27 on the far right hand side of the AC controller (4th image) and it is involved with the mode door actuator, or one of the other doors.

If I had to pick a pin for that grey wire to go to on the AC controller, it would be 21, 22, 29 or 30.

Beyond that it is starting to get difficult. If you look on the top of the first image yo will see 4 * notes describing which engine the various * notes scattered around the diagram refer to. Look next to the ECU plug and you will see 1 referring to RB20E, one referring to RB25 (and I think that solves the issue of pin 36 and 31 both being connected together - they probably aren't in the real world, only on a drawing that serves 2 different engine/ECU combos). So I think you need to consider what engine you originally had and what you changed to, where the old and new wiring looms are now and whether the power supplies from the fuse box (visible in the middle of image 1) are all connected where they should. By that last, I mean at least one power wire comes from that fusebox down to things like the cabin air temp sensor and on through connector A into the ECU (on the P wire HB05)

[nicostar]

15 hours ago, GTSBoy said:

Alright....looking at the 2nd of those images, I see that ECU pin 36 (and apparently ECU pin 31) are connected to the FICD solenoid valve. That's the Fast Idle (Control Valve, I guess). Used for idle up. So when the Air-con sends a signal out on that same connection, the idle speed will increase. Easy enough. What I can't easily read from the AC controller end of that grey wire is which pin it is connected to. But it's definitely not pin 27, because I see pin 27 on the far right hand side of the AC controller (4th image) and it is involved with the mode door actuator, or one of the other doors.

If I had to pick a pin for that grey wire to go to on the AC controller, it would be 21, 22, 29 or 30.

Beyond that it is starting to get difficult. If you look on the top of the first image yo will see 4 * notes describing which engine the various * notes scattered around the diagram refer to. Look next to the ECU plug and you will see 1 referring to RB20E, one referring to RB25 (and I think that solves the issue of pin 36 and 31 both being connected together - they probably aren't in the real world, only on a drawing that serves 2 different engine/ECU combos). So I think you need to consider what engine you originally had and what you changed to, where the old and new wiring looms are now and whether the power supplies from the fuse box (visible in the middle of image 1) are all connected where they should. By that last, I mean at least one power wire comes from that fusebox down to things like the cabin air temp sensor and on through connector A into the ECU (on the P wire HB05)

please note that the diagrams are showing 2 different sets of ecu connectors, the rb20e and 25de/det and 26dett. also take note of the numbering KEY/LEGEND   
ie. *1
*2
*3
*4

as these indicate which wiring is for which car. I don't use a FICD nor relay for it on my current engine and neither did the stock rb20e that came in the chassis.
 

ok I read your post further and realized that you saw that.

Edited July 24, 2019 by nicostar

[nicostar]

15 hours ago, GTSBoy said:

Alright....looking at the 2nd of those images, I see that ECU pin 36 (and apparently ECU pin 31) are connected to the FICD solenoid valve. That's the Fast Idle (Control Valve, I guess). Used for idle up. So when the Air-con sends a signal out on that same connection, the idle speed will increase. Easy enough. What I can't easily read from the AC controller end of that grey wire is which pin it is connected to. But it's definitely not pin 27, because I see pin 27 on the far right hand side of the AC controller (4th image) and it is involved with the mode door actuator, or one of the other doors.

If I had to pick a pin for that grey wire to go to on the AC controller, it would be 21, 22, 29 or 30.

Beyond that it is starting to get difficult. If you look on the top of the first image yo will see 4 * notes describing which engine the various * notes scattered around the diagram refer to. Look next to the ECU plug and you will see 1 referring to RB20E, one referring to RB25 (and I think that solves the issue of pin 36 and 31 both being connected together - they probably aren't in the real world, only on a drawing that serves 2 different engine/ECU combos). So I think you need to consider what engine you originally had and what you changed to, where the old and new wiring looms are now and whether the power supplies from the fuse box (visible in the middle of image 1) are all connected where they should. By that last, I mean at least one power wire comes from that fusebox down to things like the cabin air temp sensor and on through connector A into the ECU (on the P wire HB05)

I have no problems with power going to the HVAC unit or any of the sensors, I just can't get the ac button to do anything with any wire, hence I am trying to find out what this pin 36 wire goes to in actuality regardless of which ecu, It is the only wire I have left disconnected and out of the whole equation, if it helps my outside ambient air temp sensor recently took a dump but these problems were there even when it was working (checked using the HVAC self diagnosis) I also fixed my hot air actuator thanks to the diagnosis. 

[GTSBoy]

If you chase the wire back from the compressor and its relay, via the refrigerant pressure switch, it goes down through the small engine loom connector M and on to ECU pins 40 & 9 (which are marked as being RB20 specific).

Which engine did this car originally have? RB20E, or RB25DE?

The power that runs the compressor comes out of the 2nd 10A IGN fuse in the box. Runs out and down to the cabin temp sensor & up to power both the relay and the compressor directly.

So the switched side of the compressor has to be switched somewhere.The only other wire on the relay goes over to the pressure switches, as I said in my first paragraph. So the ECU has to be responsible. and the ECU needs to receive a signal from the AC controller, and that really looks like the wire I was talking about in my first post.

I can't see how it would work otherwise. I can't even see how they would be able to make it so that there might be a different (simpler) control unit for the cheaper car (say, the RB20 one, which might not have climate control**) and the full climate cars. They all look to be mostly the same on that diagram.

** I think R32s and the S chassis cars were like that.

[nicostar]

9 hours ago, GTSBoy said:

If you chase the wire back from the compressor and its relay, via the refrigerant pressure switch, it goes down through the small engine loom connector M and on to ECU pins 40 & 9 (which are marked as being RB20 specific).

Which engine did this car originally have? RB20E, or RB25DE?

The power that runs the compressor comes out of the 2nd 10A IGN fuse in the box. Runs out and down to the cabin temp sensor & up to power both the relay and the compressor directly.

So the switched side of the compressor has to be switched somewhere.The only other wire on the relay goes over to the pressure switches, as I said in my first paragraph. So the ECU has to be responsible. and the ECU needs to receive a signal from the AC controller, and that really looks like the wire I was talking about in my first post.

I can't see how it would work otherwise. I can't even see how they would be able to make it so that there might be a different (simpler) control unit for the cheaper car (say, the RB20 one, which might not have climate control**) and the full climate cars. They all look to be mostly the same on that diagram.

** I think R32s and the S chassis cars were like that.

the r33 I have came with rb20e, it has the 2 pin pressure switch on the dryer. I have an rb20det now from r32. The original engine loom was cut up by a shoddy electrician at the time, I am trying to correct it now. If I ground the green with red strip wire for the compressor it will turn on perfectly fine, The thermo amp looks to be working, I connected what I could find regarding where they should go, the pin 36 wire is the only on I don't know where to put on the ecu. I've checked another Rb25 from an R33 and there is no pin 36 either totally blank. that r33 has a black tag ac controller where as mine has yellow tag so the wiring pinouts appear different or I could have used that to trace where the wire goes on ecu. 

Edited July 24, 2019 by nicostar

[GTSBoy]

You got the R32 (ECU) wiring diagram? It's in the R32 GTR manual.

[nicostar]

5 hours ago, GTSBoy said:

You got the R32 (ECU) wiring diagram? It's in the R32 GTR manual.

pin 36 is blank on the r32 20det ecu based on the diagram, only the rb26 (gtr 32) has 36 for intake air temp sensor. but looking at that diagram I still can't pinpoint where the wire from r33 ac control unit pin 27 would go, I know the r32 has a similar setup but the pins are different.

[nicostar]

[GTSBoy]

Yes, so, what you want is the ECU pin on the R32 RB20DET ECU that the R32 AC controller sends its signal to. Whatever pin it is. Then bang the signal from the R33 AC controller in. Unless they are not compatible in some way (because of doing things backwards relative to each other, for example).

On that R32 wiring diagram there are 3x different AC controllers shown, towards the RH end. At the top of that you will see the AC relay. viz

If you follow the wires down from that towards the full auto controllers, you will see that one of them comes out of T10 on one controller and T15 on the other. At the top end of that wire there is a flagged 21. You can see it in the image above.

On the ECU end of the diagram there is also a flagged 21. That is ECU pin 46, which coincidentally, is the same pin identified on any RB20 ECU pinout, like this one.

 

I'm sure if you study the way that these are hooked up you should be able to mimic it with the R33 controller.

[nicostar]

14 minutes ago, GTSBoy said:

Yes, so, what you want is the ECU pin on the R32 RB20DET ECU that the R32 AC controller sends its signal to. Whatever pin it is. Then bang the signal from the R33 AC controller in. Unless they are not compatible in some way (because of doing things backwards relative to each other, for example).

On that R32 wiring diagram there are 3x different AC controllers shown, towards the RH end. At the top of that you will see the AC relay. viz

If you follow the wires down from that towards the full auto controllers, you will see that one of them comes out of T10 on one controller and T15 on the other. At the top end of that wire there is a flagged 21. You can see it in the image above.

On the ECU end of the diagram there is also a flagged 21. That is ECU pin 46, which coincidentally, is the same pin identified on any RB20 ECU pinout, like this one.

 

I'm sure if you study the way that these are hooked up you should be able to mimic it with the R33 controller.

Flag 21 comes from the thermo switch on the hvac unit's system similar to the one I have in the r33. I have that wire from the thermo amp going to pin 46 and pin 9 to the compressor. No dice yet. 

[nicostar]

On 7/23/2019 at 7:05 AM, GTSBoy said:

Alright....looking at the 2nd of those images, I see that ECU pin 36 (and apparently ECU pin 31) are connected to the FICD solenoid valve. That's the Fast Idle (Control Valve, I guess). Used for idle up. So when the Air-con sends a signal out on that same connection, the idle speed will increase. Easy enough. What I can't easily read from the AC controller end of that grey wire is which pin it is connected to. But it's definitely not pin 27, because I see pin 27 on the far right hand side of the AC controller (4th image) and it is involved with the mode door actuator, or one of the other doors.

If I had to pick a pin for that grey wire to go to on the AC controller, it would be 21, 22, 29 or 30.

 

pin 27 is "HB66", it is in the way left of the list over the HVAC unit right connector labeled GY, it says is goes back to 36 on ecu for rb25. Even on the rb20e ecu pinout the corresponding pin is also blank.

Edited July 25, 2019 by nicostar

[GTSBoy]

No, look again properly. The top AC controller on the R32 diagram is the manual controller. That has a thermoswitch to run that signal. Follow the wire down further from there to the two different fully auto climate control options, and on one of them it connects to pin 10 and on the other it connects to pin 15. (actually, I just saw that there's a thermo amplifier involved in the pin 10 version controller also, but nevermind, because it doesn't really change the fact that it originates at the AC controller).

I didn't know that there were 2x climate control systems in R32s, but it doesn't really matter. Either way, these both have a signal coming out of the AC controller that goes to the ECU, and coincidentally, the flag 6 at the AC pressure switch in the top RHS of the drawing also goes to flag 6 on the ECU, pin (hard to read, but could be) 8, I think. Looking at the ECU pinout above, it looks like it would be 9.

[nicostar]

8 minutes ago, GTSBoy said:

No, look again properly. The top AC controller on the R32 diagram is the manual controller. That has a thermoswitch to run that signal. Follow the wire down further from there to the two different fully auto climate control options, and on one of them it connects to pin 10 and on the other it connects to pin 15. (actually, I just saw that there's a thermo amplifier involved in the pin 10 version controller also, but nevermind, because it doesn't really change the fact that it originates at the AC controller).

I didn't know that there were 2x climate control systems in R32s, but it doesn't really matter. Either way, these both have a signal coming out of the AC controller that goes to the ECU, and coincidentally, the flag 6 at the AC pressure switch in the top RHS of the drawing also goes to flag 6 on the ECU, pin (hard to read, but could be) 8, I think. Looking at the ECU pinout above, it looks like it would be 9.

yes it is pin 9. Should go to ac compressor relay. The only pin I have missing from the equation is the GY from r33 HVAC unit that should go to pin "36", problem I have is, I don't know what pin 36 should be, I've never seen it in an R33 before, If only someone had a series 2 with loom intact that could take a pic of the GY wire and where it goes to on ecu.
My only assumption is that it could be looking for engine temp sensor based on the rb26?  

[GTSBoy]

Nooooooo. You have an RB20 ECU. Forget pin 36. You have to talk to your ECU on pin 9 and 46. I think the AC controller tells the ECU on 46 and the ECU switches the compressor out of 9. All you need is to hook the ECU up to appropriate wire out of the R33 controller.

[nicostar]

7 minutes ago, GTSBoy said:

Nooooooo. You have an RB20 ECU. Forget pin 36. You have to talk to your ECU on pin 9 and 46. I think the AC controller tells the ECU on 46 and the ECU switches the compressor out of 9. All you need is to hook the ECU up to appropriate wire out of the R33 controller.

Hmmm... well then this means something is bad, either the ecu is bad or the HVAC unit is bad, any way to test this without a spare ecu or hvac unit? Do you know if it's possible to bypass the ecu and make the hvac unit trigger the compressor directly (of course if there is a way and it doesn't work it would indicate a faulty hvac unit)?