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C4 Grand Picasso 2012 Aircon failure and DIY repair	Please Register to enjoy additional Member Benefits

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Zapaction99 United Kingdom

Wed Jun 21 2023, 04:11pm

Member No: #57397

Joined: Dec 20 2020
Location: Soutport

I recently fixed my car’s air conditioning so I thought I’d write a few notes in case it helps someone else.

Car is 2012 C4 Grand Picasso Vtr+ E-Hdi A, 75K miles

Symptoms – pressing the aircon button caused the green dash light to go on but no cold air was coming out of the vents. Observed the aircon clutch was not engaging. Refrigerant levels were checked by a garage - okay.

Autel reported code C994 – aircon compressor clutch control fault. I measured the compressor clutch field coil resistance – 69K Ohms (should be 2.8-4.4 Ohms according to manufacturer). So, bad coil. Checked that when the aircon button is on that the coil supply wire was reading 12V – it was actually a healthy 14V. This proved the BSM relay was still working. After removing the old clutch coil there was evidence of some rust around its wiring – possibly water ingress. It has a built-in diode – maybe that failed?

After doing some research and taking some measurements, I determined that replacement of the coil is doable with the compressor on the car. Of great help were two Youtube videos – these aren’t specific to the C4 but all compressors are similar: - Click Here - and - Click Here - .

The compressor fitted was a Saden NORM R134a SD7C16 (OEM 9800839580) and Thermotec KTT030074 O/D 103mm, width 33mm is a good match for my car. The only issue is the yellow plug which was subtlety different but more about this later.

Tools used:
Multimeter to measure voltage, Ohms and continuity, 17mm wheel nut spanner, trolley jack and axle stand, socket set (10mm, 14mm hex sockets and 10 inch extension), flathead screwdrivers to remove wheel arch clips, torx screwdriver to remove under engine tray and wheel arch screws, long straight circlip pliers (Laser brand from Halfords), 150mm 3-arm gear puller, rubber mallet, low range torque wrench, angle grinder two-pin spanner, 17mm spanner to remove tension from serpentine belt, two 4mm metal rods to temporarily hold the serpentine belt tensioners back.

Access is a case of jacking up the front, removing the under engine tray, removing the driver’s wheel and wheel arch lining. Then there is an inner plastic shield, the front part of which can be undone (one nut, two bolts) and slid backward to reveal the aircon pulley. After noting the rotation direction and removing the serpentine belt (mine has two tensioners - stop/start system - just to add to the fun) I used the angle grinder spanner to stop the clutch plate turning whilst cracking off the nut with a 14mm socket. It’s only 18Nm torque so not too tight. It’s a normal thread (i.e. not reversed or anything odd). The clutch plate came off easy – remember to catch any shim washers. The pulley circlip (note orientation for reassembly) was easy but I definitely needed a gear puller to get the pulley off the shaft – there’s just enough room to get the tool engaged. The inner ‘coil’ circlip needs pliers that can open to at least 30mm – the Laser ones from Halfords did the trick. The coil then came straight off after unclipping the electrical lead from the compressor block.

Assembly is the same but in reverse. Note that the coil has a pin on the back that needs to engage with a depression on the clutch body – this stops the coil spinning. Holding the coil in place whilst replacing the inner circlip was the hardest part – ideally you need three hands. Got there after a lot of swearing! The pulley bearing was still good so I slowly tapped it back on using the rubber mallet. Keep going until the outer circlip groove appears. Outer circlip was a relative doddle, remember the shim washer before re-installing the clutch plate and M8 armature nut (torque 18Nm according to Saden). Serpentine belt back on (you did draw a diagram to note how it’s threaded on, didn’t you?) and tensioners released.

At this point I discovered that the yellow plastic clip on the new coil didn’t quite match the other side of the connector still on the car! Not wanting to cut and solder, I sourced a plug from ebay (item 255582190638, not exact but with some fettling I got it to fit) and made a short, well-insulated link consisting of the new plug and the old plug from the bad coil. I made sure I used the same gauge of wire; according to Saden the coil draws 4Amps, so didn’t want a melting wire! After checking the aircon was fixed (clutch now engaging – yeay!), the wiring was zip-tied up before replacing the engine under-tray. Job done and just in time for the summer holidays – it’ll be the coldest on record now, what’s the betting!

Conclusion – not too bad a job provided you have the necessary tools and somewhere to work out of the rain. Took me about 3 hours all in. The coil was around £28. Fortunately the BSM relay was fine as otherwise this would have been a lot more complex – the relay is potted with resin so I would have had to replace the BSM.


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