DS5 2.0hdi intermittent aircon

[Justin_Brown]

Hi All,

2014 DS5 2.0hdi with an intermittent aircon issue (VIN VF7**************[VIN obfuscated, can be read by forum staff]

The car has spent the last 2 days at an aircon specialist with no luck other than the issue is electrical (system evacuated, pressure tested and re-filled with 450g R134 A) . The issue presents as follows; When the vehicle is first started (from cold) the aircon functions as it should with the AC clutch springing to life shortly after engine start. However, once driven and the vehicle reaching operating temperate the AC clutch loses it’s 12v feed resulting in the AC clutch clicking off (the AC light on the control panel remains on).

There are no stored or active engine codes and while the AC is operational the external AC gauges reflect the same pressure that is reflected on the scan tool.

Years back I had a similar issue on my C4 (with manual AC, not climate control) which turned out to be a faulty relay on the BSM which would stop making contact when under bonnet temperatures increased.

Any recommendations welcome to properly diagnose the issue.
Thanks in advance,

[xantia_v6]

It needs careful checking of live data from the engine ECU and BSI to check that all conditions necessary for A/C operation are met. Our 308 had similar symptoms with a failing electrically controlled water thermostat.

[Justin_Brown]

Your 308, I'm assuming this was the later 1.6 petrol (BMW derived) as these have electronically controlled thermostats. In my instance the 2.0hdi has a normal thermostat with temperature sensor.

[ozvtr]

Years back I had a similar issue on my C4 (with manual AC, not climate control) which turned out to be a faulty relay on the BSM which would stop making contact when under bonnet temperatures increased.

The modern BSMs use electronics (FETs) to drive the compressor clutch. If you are having hot weather ATM I would say that's your problem. The system is pretty simple, everything is done over the CAN BUS communications lines. If the CAN BUS wasn't working you would have lots of problems!
You could check to see that the A/C compressor clutch fuse is secure and tight in the BSM. But that's all that I've got.
Older BSMs were "potted" in RTV. Not a bright idea in hot environments...like under the bonnet in the southern hemisphere!
I don't know if modern BSMs are potted. But either way, I would say PSA has found a way to make the BSM unreparable.

[Justin_Brown]

Having performed a BSI reset I now get a permanent fault code B1310 01 Passenger compartment air blower repeat signal fault. I suspect the AC blower control module to be at fault, however there are a number of things I find strange;
1. If I set the interior blower to windscreen de-mist and clear the code the aircon comes back to life and blows ice cold right up to the point the de-mist function is turned off and air flow is diverted back to the normal vents.
2. Looking at live data (image attached) the “passenger compartment air blower supply voltage jumps between “5V” and “Blower faulty”. However, measuring the voltage directly on the blower indicates that the blower receives anywhere between 6V & 12v depending on the fan speed selected on the car’s climate control panel. So the questing is what reports the blower voltage back to the ECU, I would assume the blower control module?
3. The blower was removed and bench tested, all checked out. No sparking, the bearings spin freely and the blower motor all round performs as expected.
4. The wiring from the AC control module to the AC ECU as well as the respective earthing points were checked and confirmed to be in order.

In closing is there a way in which I can confirm the AC control module to be at fault, i.e known resistance values across the 5 pins I can measure?
Thanks,

[Justin_Brown]

Having performed a BSI reset I now get a permanent fault code B1310 01 Passenger compartment air blower repeat signal fault. I suspect the AC blower control module to be at fault, however there are a number of things I find strange;
1. If I set the interior blower to windscreen de-mist and clear the code the aircon comes back to life and blows ice cold right up to the point the de-mist function is turned off and air flow is diverted back to the normal vents.
2. Looking at live data (image attached) the “passenger compartment air blower supply voltage jumps between “5V” and “Blower faulty”. However, measuring the voltage directly on the blower indicates that the blower receives anywhere between 6V & 12v depending on the fan speed selected on the car’s climate control panel. So the questing is what reports the blower voltage back to the ECU, I would assume the blower control module?
3. The blower was removed and bench tested, all checked out. No sparking, the bearings spin freely and the blower motor all round performs as expected.
4. The wiring from the AC control module to the AC ECU as well as the respective earthing points were checked and confirmed to be in order.

In closing is there a way in which I can confirm the AC control module to be at fault, i.e known resistance values across the 5 pins I can measure?
Thanks,

Update;
Pins 1 & 2 of the blower control module are signal feeds to/from the AC ECU.
The blower motor control module was removed and there appeared to be some or other film over pin 1 which was subsequently sanded off. The control module was then re-installed and the corresponding fault code cleared.
By the looks of it pin 1 of the control module carries a reference voltage back to the AC ECU measuring between 1v to 5v. This signal voltage is proportional to the fan blower speed.
To confirm the connections pin 1 was back-probed while live data of the AC ECU was being read. The reference voltage read by the ECU corresponded to that of the back-probed reading meaning the ECU was reading and interpreting the signal correctly.
In conclusion the AC compressor has come back to life and is operating as expected and no permanent/intermittent fault code has returned.

[ozvtr]

You didn't mention anything about the interior fan in your original post, only the compressor clutch.
Was the interior fan still working while the AC was not?
Scan tool did not reported a fan controller fault? Despite the AC ECU detecting a fault and shutting down the AC?
But good catch anyway.