BNR32 Climate Control Unit

[BourneToLive]

Hey, 

I am in the process of diagnosing my air conditioning issue my car. I’ve made another post before about trying to find out why a specific AC fuse was blowing, that was unrelated to the compressor, and saw that I had a scorch mark on the circuit board inside the climate control unit. I bought a new one from an auction and it worked! But the next day, while I was driving and the AC was off, a hole had burnt through the board. Of course, I suspected something along the lines of a short to signal wire or to ground because when I removed all fuses and relays and started poking around the connectors with test light, one wire lit up (video below). Whatever it was, it was sending power down the wrong path or too much power. Anyway, to the point of this post, I brought it to a local mechanic to inspect the wires and he said other than 13v reading in a 12v system, nothing seemed out of the ordinary. He said the problem could be because of the type climate control control unit I bought from the auction and if it was from an early model R32 or a late model R32. He claims that it has to be close to the original as possible. I have a late model R32 GTR from 08/1994. Am I able to use any climate control unit from any other 89-94 R32 GTR or is it specific to the exact year? I will attach pictures of my climate control part number and the one from the auction. The top two rows are only one digit off. My original one is on the top. I read a post of someone using an R33 climate control unit in an R32 and it worked. 

 

 

 

Edited July 8, 2022 by BourneToLive

[GTSBoy]

I wouldn't presume that an R33 one would work in a 32, but it's maybe possible. I would, on the other hand, assume that all R32 climate control boxes would work on all other R32s, because as far as I know the pinout never changed and the functionality never changed.

13v is close enough to the correct voltage of a fully charged 12V battery. They should sit at 12.7 - 12.9V anyway.

Get the wiring diagram out, and start working out which wire is which, and which wire has power on it (and whether it should or shouldn't have power on it) and go from there. Just poking with a test light is not troubleshooting. You have to understand what you see and what you're looking for.

[BourneToLive]

On 7/8/2022 at 5:26 PM, GTSBoy said:

I wouldn't presume that an R33 one would work in a 32, but it's maybe possible. I would, on the other hand, assume that all R32 climate control boxes would work on all other R32s, because as far as I know the pinout never changed and the functionality never changed.

13v is close enough to the correct voltage of a fully charged 12V battery. They should sit at 12.7 - 12.9V anyway.

Get the wiring diagram out, and start working out which wire is which, and which wire has power on it (and whether it should or shouldn't have power on it) and go from there. Just poking with a test light is not troubleshooting. You have to understand what you see and what you're looking for.

Thanks for clarifying. 
My car was off when I removed all fuses and relay and used my test light. Should the AC have constant power even when the car is off? I’m not familiar with electronics. I attached a pic of the climate control unit diagram. I suspect the green cable I tested was pin 10. 

[Duncan]

The Part Supersession chain in FAST says:

28525-05U17 goes to 28525-05U12 and 

28525-05U16 goes to 28525-05U11 and 28525-05U12

So, the parts are interchangeable (there might be a different in the colour of the globes or texture but they should work OK).

Next, I think you should get a different mechanic, or take this issue to an auto electrician. A "12v electrical system" runs at 13.x volts when the alternator is turning.

Finally, what is the actual issue? Did a first and then replacement AC control unit stop working? How did you notice them fail? Have you got a pic of the failure?

[BourneToLive]

On 7/9/2022 at 6:52 AM, Duncan said:

The Part Supersession chain in FAST says:

28525-05U17 goes to 28525-05U12 and 

28525-05U16 goes to 28525-05U11 and 28525-05U12

So, the parts are interchangeable (there might be a different in the colour of the globes or texture but they should work OK).

Next, I think you should get a different mechanic, or take this issue to an auto electrician. A "12v electrical system" runs at 13.x volts when the alternator is turning.

Finally, what is the actual issue? Did a first and then replacement AC control unit stop working? How did you notice them fail? Have you got a pic of the failure?

The issue I’m having is that something is burning my circuit boards. The first picture is of my original climate control unit, which was blowing my fuse. 

And the next pictures are of the second climate control unit I bought recently, which didn’t blow any fuses. 

[Duncan]

Oh dear, that is not going to work very well.

So that diagram you posted earlier looks excellent, I'd go through each pin on the car side of the control until and make sure it is what the diagram days.

Specifically, first check the earths 8, 23, 32 and I think 16 all have good continuity to a known good earth in the car. If any of them have 12v when compared to an earth you have a short in the wiring there

Then check the power circuit - 1, 2, 3 should have 12v with key off (BAT), IGN and ACC respectively. Beyond that, any pin with 12v with the IGN on is a suspect to check (because the control unit is getting + where it should have -, or vice versa)

Then check every other pin, this is trickier but most likely where the issue is. The diagram isn't necessarily obvious, but just keep in mind everything electric needs power and earth to operate (eg blower motor + must be pin 1 because it comes from ACC fuse 4, so pin 2 must be earth, which means the HI relay connects pin 3 to 5 (earth) and therefore AC control pin 17 should be earth when fan control is on high (and control unit pin 5 which goes to HI relay 1 is an earth signal from the unit to the relay). In the case of switches like the intake door actuator it could be either + or - switched (a bit hard to tell unless you know if ECU pin 9 is + or -), and sensors are the same, they will either be + or - in, and a resistance to the input to send a signal (generally negative/earth input)

[Duncan]

Sorry, 2 things to add.

Most likely the issue is something that turns on from the unit, not something that is always on. If it was always on like the earth or power circuits, it would blow as soon as you plug it in or turn the key on.  I think you said it blew when you were driving so you saw it working at some stage after you started the car, but later it wasn't. If you can work out what changed between it working and not that is your first place to check, eg did you change the fan level. Of course it is climate control so fan speed can change based on sensor inputs so it may not be obvious.

The other is, the most likely wiring issue in an old car is that a wire has rubbed through somewhere and is shorting to earth. Maybe all the time, maybe intermittent eg going around a corner or braking. So most likely you have earth somewhere that expects +, and you might be able to find it by seeing damaged wiring, depending how much of the car is apart.

[BourneToLive]

I appreciate the advice and what route I should take to find the issue. This will take me some time to do, so an update will come a little late. I’m debating whether I should just get an entirely new harness or not, or if the issue could be in the mode door actuator (blower motor). I’ll provide an update as soon as I have one. 

[Duncan]

Sorry there doesn't seem to be a quick solution. If you are not confident chasing the wiring I suggest an auto electrician. Buying a new loom might help but might not as there are multiple looms in the car and you don't currently know which one is the issue.

BTW you first unit probably still works fine since it blew the fuse, not the unit itself, so that is the good news

[BourneToLive]

Alright. I was able to do a simple test using my test light and found that there’s a short in the interior clock harness. I removed the negative cable from the battery terminal and clamped one end of the test light to it and the other to the negative terminal and my test light lit up, just barely. I started unplugging fuses until I found the one that put out the test light and it turned out to be my interior clock. After removing the fuse that powered it (fuse 23- BAT electrical part fuse in the bottom row), my original ac unit started working again without blowing the AC fuse (fuse 20). I’m contemplating also unplugging the clock so it gets no power at all. 

[Duncan]

Great outcome, and those clocks are by far the least reliable electronic component in the whole car. Generally they just stop working rather than blowing up your AC though!

Having said that, it is definitely worth unplugging the clock to confirm that is the issue, there are a bunch of other things that power from that fuse including Radio, HICAS control, something in the AC control (as you found), Auto trans for auto cars

[BourneToLive]

On 7/20/2022 at 5:56 AM, Duncan said:

Great outcome, and those clocks are by far the least reliable electronic component in the whole car. Generally they just stop working rather than blowing up your AC though!

Having said that, it is definitely worth unplugging the clock to confirm that is the issue, there are a bunch of other things that power from that fuse including Radio, HICAS control, something in the AC control (as you found), Auto trans for auto cars

That fuse controls all that? I’ll try unplugging the clock and putting the fuse back in to see if the issue persists.