MES 4.0 & 147 Pre Facelift air Conditioning

[Citroënbender]

Bit confused here.

AC doesn't seem quite right, had remade the failure prone front hose last May and gassed up with new R/D and seals.

I can only get either zero or fully recirc on the parameters yet the button has three options, and of the four internal parameters Left 1&2, Right 1&2, only three readings. One of them is always 0°. No reading on the solar energy, either side.

There's nowhere it shows whether the compressor is authorised to engage, and upon attempting the actuations, all fail.

[bazzbazz]

Compressor engagement is managed through the Engine menu.

And you are only suppose to get full or no recirculation. The 3 positions you are referring to are the orange/amber lights on the recirculation button, am I correct?

Pressing the recirculation button determines three possible types of operation, in order, according to the following logic:

1. automatic recirculation (amber LED on)  (Right light)
2. forced recirculation closed or on (passenger compartment inside air, orange LED on). (Left Light)
3. forced recirculation open or off (passenger compartment outside air, orange LED off - amber LED off).  (No lights)

Also the Electronic PTC heating system was only fitted to "Cold Climate" countries and to Diesels.

As for the L & R sunshine sensor readings, were you in the garage when you were doing this?   

I should also point out, that depending what year your car was built, it will have different environmental "Packs" & sensors fitted.
Also if at any time you disconnect your battery, on reconnecting the Climate system must be allowed to run for at least 1 minute to allow the system to recalibrate all vents, flaps, controls & sensors.

[Citroënbender]

Thanks for the pointers.

Seems the recirc button is doing its thing correctly; I was outside when testing the system so expected some variation in the sunlight sensor when covered/not covered.

Got a fair idea of the aux heating systems not fitted here (both the diesel types and heated pipe units), feel I can identify these in the menu. But had presumed that the dual zone system may have two outlet sensors per side - perhaps this was in error and it has one sampler fan with sensor plus two in-duct sensors for a total of three. More familiar with the Valeo units in French cars.

I was puzzled to see no data sample for the pressostat, the only actual refrigerant control I could view was seeing the temporary change of state when the AC button is pressed. Will look for the compressor actuator test in the engine menu this time.

[bazzbazz]

Dual zone is supposed to have four treated air temperature sensors.

Two are positioned in the duct which directs the air to the lower (floor) vents and the other two are near the centre vents (vent).

[Citroënbender]

I'm pinning by this as an intermittent fault, probably an interconnect. Couple of good bumps and on comes the AC... Time to start checking harness plugs!

[Citroënbender]

Had a brief Uncle Merv yesterday when installing the Bluetooth adaptor. The RHS location for a "down air" thermistor has a dummy plug in it, the LHS has the sensor. Bit puzzled because at one point I'm sure there were four actual readings displayed...

Also tried actuating the compressor clutch via the engine menu; no dice. So I'm betting on a simple wiring issue.

[bazzbazz]

May I suggest you see if the cigarette lighter is working. If not check the fuse for the cigarette lighter, it is also the fuse for the A/C compressor clutch. 

[Citroënbender]

It works dependably, powering a pair of 2.1A USB outlets. 

The climate panel has some quirks IMO, it's one of the few that will display an apparent AC clutch request (by the snowflake being lit) when there are absences of suitable conditions - like pressostat out of range.

[bazzbazz]

Check you are actually getting power to the A/C clutch when the relay is energised, the wire going to the clutch gets very brittle from heat and has a tendency to break along the line somewhere. Also could be a faulty relay.

[Citroënbender]

I can clutch it in by jumping the relay, so yep, either a faulty relay coil or the signal is disappearing somewhere between control panel and underbonnet fusebox.  Enslaved for a few weeks now, will chase it down in late May/early June. 

[Citroënbender]

Faulty relay - confirmed by test swapping with horn relay (identical part). That gave a healthy clutch pull-in and an unreliable, feeble, toot on the horn.

[Citroënbender]

A more technical digression here, having spoken at some length with my AC mate about root causes.

The compressor air gap is presently excessive, probably from both initial assembly at the upper end of tolerance and then clutch plate wear. More gap, less grip, slip leads to clutch heating and further loss of grip. Relay also draws more steady state power closing the excess air gap, it is a design where the leaf spring of the moving contact is also the conductor. So it's likely to erode the contact buttons and possibly even draw the spring's temper slightly.

The long term fix, which I'll probably do in a few weeks with a clutch puller to hand, is to adjust the clutch shim pack. My mate basically said he sets them close as possible with no scuffing, which is tighter than the Sanden spec (around 26 thou max, IIRC). I'm sure Sanden have their reasons but I'm not going to go against a "feet on the ground" recommendation.