Citroen c3 2008 No AC detected by Lexia

[areid]

I had planned for a few days to take a look to this matter. But I ended up going on holiday.
When I left the A/C worked, that is, the compressor started and cycled two times, and then never again. This happened once a day. I could also connect to the A/C ECU and test the actuators.
I'm now back home and the A/C is not working. The compressor never starts and I only get outside air that has circulated through the engine space. I can smell the humidity in the air coming out of the vents. When hot is selected I get air that went through the engine space.
I tried connecting to the A/C ECU with Lexia to try the actuators, but Lexia refused saying there's no A/C present.
Ozvtr, thanks for the circuit diagrams. As per your suggestion I'll take a look first to the A/C ECU. Where is it physically located? And how do I test it? I'm no electrician...
Also, could the problem be as simple as a blown fuse?

[ozvtr]

So let me get this straight. When the AC works the AC ECU appears in LEXIA? And when the AC is not working, the AC ECU disappears in LEXIA?
It cant be a fuse, power supply or earth issue. It shares earths and fuses with the dash. So that would go out too.
The AC ECU IS the control panel, with the knobs and switches.
You could check the security of the connector on the back of the control panel. Take the storage box out of the dash above the control panel and below the radio.
It's possible that it's a faulty control panel?

[areid]

I'll take a look today. I recently installed a Bluetooth adapter to connect my phone to the radio. I took out the radio and the box, moved cables a bit, and then put back everything (that's the reason why I ended up buying a Lexia in the first place). Perhaps all the fumbling around disconnected something. However, the A/C light still turns on when pressing the A/C button on the control panel. It's got the back lights on as well.
As per what is the A/C ECU, i thought you were pointing to check the connectors in what I assume know is the BSI (a gray metal box sitting on the side of the battery).
I'll take some pictures of everything and post them here to clarify what is what.
And just to review, until the end of January the A/C worked. That is, the compressor kicked in at least once a day and I could see the A/C in Lexia and test the actuators (that's where I took the pictures previously posted). As of the end of February, the A/C does not work at all. That is, the compressor does not engage when turning the A/C on and Lexia says it cannot communicate with the A/C ECU.

[ozvtr]

The AC ECU "talks" to the rest of the car over what's known as the CAN BUS. This also means that the car talks back to the AC ECU, over that CAN BUS. So when YOU turn the lights on, the CAR "TELLS" the AC ECU (the control panel) to turn the back lights on. So if the back lights come on, there is communication over the CAN BUS. AND there is power
It's not like the old days where there was a wire that carried power from the lighting circuit to the backlights of the various panels. The headlight switch tells the rest of the car, over these BUSES, that the lights are on and to turn on the various backlights and headlights and whatever.
Do you understand the ramifications of this?
The AC ECU cant "listen" to the car on one hand but not "talk back" to the car on the other. It's all or nothing. This is not making any sense.
OR are you saying the back lights are permanently on?? OR are you saying the back lights come on uncommanded when the AC ECU "disappears" from LEXIA? Or what are you saying?
I'm looking for a sign that the AC ECU stops talking to the rest of the car. Or is acting up or something unusual. But if the backlights work as advertised AND LEXIA cant see the AC ECU...I've got nothing. It doesn't make sense.

Have we established that LEXIA cant see the AC ECU when the AC stops working? AND, that LEXIA can see the AC ECU when the AC is working?
Are the backlights of the AC control panel working correctly, ALL THE TIME?

[areid]

I understand what a CAN BUS is and how it works, that is, that it goes both ways.
I'm also trying to make sense of this situation and in no way am trying to be misleading. I apologize if my explanations are not clear enough.

I just connected Lexia to the car and run the global diagnosis as well as the specific component diagnosis. In both cases the response from the A/C ECU is the same (shown in picture below).

Just so we're clear, this is the control panel/ECU for the A/C.

And this is the BSI that sits on the side of the battery under the hood.

I taped a video of what happens with the back lights of the control panel at the same time as trying to dialogue with the A/C ECU. Unfortunately I cannot upload it. But what happens is the following. After turning on the lights with the stick on the left of the steering wheel, the radio and the control panel light up (the back lights). If I turn the lights off, the control panel back lights turn off. They do not turn on/off on their own nor they are all the time on or off. Same thing happens with all the other buttons. After pressing the AC button it lights up in green, so does the rear defrost but in orange and the recirculating option in red. When turning middle knob on to 1, 2, 3 or 4, air starts to come out of the vents. But the A/C compressor does not kick in. There's no "clack" sound coming from it.

There's an option in Lexia to show the available ECUs and it shows the following.

No idea if the A/C ECU is part of any of those. Googling all those codes brought up images of the BSI posted above or similar.

I also took a look at the fuse box under the steering wheel and it only has one fuse which I believe is 5 amps.

According to my car's manual it is either the Cigarette Lighter/Digital Clock/Roof Lights/Passenger Mirror fuse, or the Digital Clock/Steering Wheel Controls/Radio/Indicators fuse. The curios thing is that the manual states that these fuses should be 30A and 20A respectively, not 5A. I pulled the fuse off and tested the roof lights, the radio, the control panel, turned the engine on/off, the cigarette lighter... everything worked fine without the fuse. I would have expected nothing to work. I really have no idea what this fuse is protecting. The only 5A fuse according to the manual is the airbags, but should be located in another position. My car has airbags...

There are more fuses under the hood, but the manual does not relate anyone to the A/C.

I'm at a loss and trying to understand what's wrong with my car's A/C unit. I do not trust A/C mechanics here, at least not yet. Sometime ago one of them told me the problem was a sensor located below and behind the control panel. I replaced and nothing changed... Also, the first thing they try to do is pull all the gas out of the system and then refill it, for which they obviously want to charge me. I've already checked for gas leaks twice and there are none. If there were, it would explain the compressor not starting. But it does not explain the no dialogue with A/C ECU.

I appreciate all the insights and help you can give me to try and sort this thing.

[ozvtr]

OK, There is a lot going on here.

First, a question mark is just a mark denoting that the sentence is a question. Don't take it to mean any more than that. I am just trying to convey that there are bits to the puzzle that are missing and I need more info. They are just options, not inquisitions.

Yes, that's the control panel I was thinking of. It's more than just a control panel. It's the AC ECU. Now I should make it clear that this panel DOES NOT run the WHOLE air conditioning system! All it does is "tell" the BSI whether the user wants the AC warmer or colder. Defrost is a special mode that overrides the current temperature control and runs the AC at full. The panel also controls the recirculation servo, the interior fan speed, the air distribution AND the panel backlighting. BUT all of those are independent of the AC system!

Please refer to the first circuit and circuit breakdown.

As I see it, the AC ECU is not "talking" to the BSI or DIAGBOX. BUT it is "listening" for the command to turn the backlights on. This makes no sense. Sorry.
Evidence: when AC IS working AC ECU appears in LEXIA. When AC IS NOT working, AC ECU does not appear in LEXIA.
Again, it's not that the AC panel isn't working...it's just not talking. I don't get it. Pending further clues...I'm stumped!
It still comes back to the control panel and some bizarre failure mode.

Next. The device in your pictures is the engine ECU. While it can shut the AC down, it's not relevant to this discussion.

This is the BSM and it's location. I have removed the battery and cover for clarity.

This is a MK1 BSM. Your electrical connectors will be different colours and shapes. But this is where it's located.

This is the BSI. It's on the left hand side of the cabin. It's in the glovebox of a right hand drive car. Next to the steering wheel of a left hand drive car.

In your case, its under that fuse block.
Again refer back to my first circuit diagram and breakdown.

Do you have any other clues at all?

[areid]

Thanks for all your explanations. Based on that, below are pics of my C3's BSI and BSM, respectively. This is a 2008 C3, diesel engine, steering-wheel on the left side. I'm now quite clear as how the whole A/C system works and the roles played by each part in the process.

Now that I've found the fuses I pulled F14 (Blue, 15Amp) just for the sake of it and checked it. According to my car's manual this fuse is in the A/C circuit, and it also appears on the circuit diagram you provided. As expected, the fuse is OK.

Just to summarize, my A/C is manual as can be seen in the images posted before. Also, in the past (as of the end of January) the compressor kicked-in and I could see the A/C ECU in Lexia. As of today, the compressor does not kick-in (tried both with the engine on and off) and I cannot see the A/C ECU in Lexia (again, tried both with the engine on and off).

The only change I can recall between January and today is that I installed a Bluetooth adapter to the car's radio to have a hands-free unit paired to my mobile. This is what I installed:

As can be seen, the BT adapter has a bridge harness. The original harness connects to the bridge, and the new harness that connects directly to the radio receives the BT adapter connector. After physically connecting, the Aux1 port has to be enabled in the radio with Lexia. I must say it works like a charm! I was careful not to change any other configurations.

I strongly doubt it, but could it be that either this bridge harness is somehow affecting the dialogue with the A/C ECU? Or that during the installation either the connector to the control panel or a CAN BUS cable was damaged?

The two things I'll try tomorrow (today's too late, sorry) are:
i) take off the bridge harness and disconnect the BT adapter and see what happens (don't expect much change), and
ii) pull the control panel out and check/test the connector. I'd appreciate help on this. I have no idea how that looks once unplugged (have not found an image on the web) and thus have no idea how to identify which pin is which. And once identified I still don't know how to test it with a multimeter.

If all this fails, then I believe I should move on to the compressor itself and start checking connections. Any suggestions are welcome.

Thanks for your patience and guidance.

[ozvtr]

The only change I can recall between January and today is that I installed a Bluetooth adapter to the car's radio to have a hands-free unit paired to my mobile.
I strongly doubt it, but could it be that either this bridge harness is somehow affecting the dialogue with the A/C ECU?

I honestly don't know. If it's the type of adaptor I'm thinking of, it just acts like it's the CD stacker. However the CAN BUS does pass through the radio to the CD stacker, so I guess it's possible. I would attempt to put everything back to "stock" including "removing" the CD stacker in LEXIA.

Or that during the installation either the connector to the control panel or a CAN BUS cable was damaged?

No, I doubt that. The panel effectively works, it listens but wont talk on the BUS.

ii) pull the control panel out and check/test the connector. I'd appreciate help on this. I have no idea how that looks once unplugged (have not found an image on the web) and thus have no idea how to identify which pin is which. And once identified I still don't know how to test it with a multimeter.

Pull the storage holder out from above the panel. The panel is held in by 2 torx headed screws and a metal plate. They are on the back of panel, attaching the panel to the console. Remove the screws and metal plate. The panel will still be held in place by 2 "ears" or clips, at either end of the panel. You will need to pry them away from the back of the console with a flat bladed screw driver. It may be easier to remove the radio, to get more room. I'll try and get a picture of the back of the panel. But it might not be for a day or so.

[areid]

Got some free time this morning and managed to test a few things.

First, took out the radio, disconnected the bridge harness that has the BT unit attached to it, and connected the radio again with the original harness. Fired Lexia. A/C still does not show up, as expected.

Second, I was able to pull the control panel out.

This is the connector

And this is the back of the A/C Control Panel.

Tried checking for continuity on all the pins in the control panel, but got no response. No idea if I did it correctly, probably not.

The same with the connector. Engine off, no key in the ignition. My leads are too thick to fit into the slots.

How can I know which pin is which as per the schematic? This is a two level connector and the schematic shows everything as a flat connector.

Thanks

[ozvtr]

Take another look at the first diagram, item 8025.
They are labeled on the panel as "rows". That is; row A and row B. A1, A2 and so on. Then B1, B2 and so on. So "top" row and "bottom" row. A hint is there are only 6 "A" pins but 8 "B" pins on the schematic.
BUT on the connector they are labeled, pin1, pin2 through to pin15. HOWEVER, pin15 is not used. So that should give you a hint. The numbering usually goes around in a circle.
Usually the connectors are labeled with at least 2 pins, the first and the last. Sometimes the first of a row and the last of a row. Cant see that printed on the face of the connector but the numbers may be some place else on the connector.
There are 2 earths on the connector, pin6 and pin7. I would make sure they have a good connection to metal parts of the chassis.

Have you done a BSI reset with the radio re-installed? look up "BSI reset" on this site.

Is the radio aftermarket or stock?

[areid]

Thanks for that. The radio is stock. Have not tried a BSI reset, but will.

Was able to get a closer picture of the back of the connector with the labels for each row.

So looking at the back of the control panel, pin A1 would be in the bottom row in the rightmost position (red circle) and pin B1 in the top row in the rightmost position (red circle).

Could not find an indication of pin number in the connector except for the 1 on each row, but with the schematics I can infer that pin 6 refers to A6 and and pin 7 refers to B3. Tested those pins for conductivity connect one probe to pin 6 and the other probe to a metal part of the chassis. The same goes for pin 7. Pin 6 (A6) gave a close to zero result measuring conductivity, while pin 7 (B3) showed a 1900 figure measuring conductivity. Are this figures correct/expected?

The schematics have three thicker lines in pins 7 (B3), 8 (B1) and 10 (B2). Are all of those ground connections as well?

How do I test the other parts of the connector and the control panel? I recall you were looking at a signal that the A/C ECU was "listening" but not "talking". I played around a bit with the control panel and a multimeter and got numbers like 1500 or 1600 when touching some B pins, which is a reflection of high resistance in the circuit. Nothing came out of A pins. Besides that, I have no idea what I'm doing.

BSI reset was completed but don’t want to assemble anything back before more testing on the control panel.

[ozvtr]

The thick lines (in the circuit diagram) B3 and B1 are the CAN BUS lines.
There CAN NOT be anything wrong with the CAN BUS or lines. 1) The instrument cluster (labled 0004 on the circuit diagram) is on that line. Any problems would cause the instrumentation not to work. 2) The back lights on the panel come on when commanded by the headlight switch.
The next thick line, B2, is power. Again, this is supplying power to the instrument cluster. Again, the backlights work and everything else works. So it has power and ground.
And you have checked both grounds.
The only odd wire is the one going from B6 to pin7 of the 10 pin black connector of the BSI. I don't know what this is doing.
Does the interior fan work? Can't remember if you told me that? All the speeds work?

I am beginning to suspect that the AC ECU not showing up on LEXIA is a red herring!

Have you looked for power on pin1 of the 5 pin yellow connector of the BSM with the AC on and engine running? Can't remember if we have gone down that path.

[areid]

Interior fan does work, all speeds OK.
Put back everything together and completed the BSI Reset. No changes as far as I can tell.
Have never touched the BSM. So far we've only covered the A/C ECU control panel following the lead that AC does not show up on Lexia. And talked about the BSI.
Will check as per your suggestion.
Perhaps it's time to take a look at the compressor itself and the connector down there.

[ozvtr]

Pin 1 of the yellow connector powers the clutch. If you have no power there, you won't have any at the clutch.
I also think that you can run the clutch actuator test from the BSI. I would find the clutch actuator test first.
Also look for AC system inhibited or not inhibited in the BSI.

[areid]

How do you get a probe into the JN 5 pin connector? The connector only has 3 wires coming out of it, but the wires have some sort of seal at the connector. Also, how do you pull that connector out?
My guess goes to the connector at the compressor, or the compressor itself.