How to Diagnose/Replace a Heater Matrix on a Citroen C4 Picasso MK2: A Complete Guide
Showing the process of diagnosing and then replacing a bad heater matrix on a 2016 Citroen C4 Picasso MK2. The Grand Picasso is obviously the same but i think given that the part number for the heater matrix is also used in a wide range of other PSA (and now stellantis) vehicles it could be an issue that others may have.
That part number for the heater matrix is: 9821299980
If you put that into google on its own, or prefix it with either PSA 9821299980, Citroen 9821299980 or Peugeot 9821299980 it should yeild a myriad of results.
Initially i noticed the heater issue myself, my aunt left the car with me in December 2023 for a cambelt change and service, i had to bleed the coolant when doing the water pump, in fact i flushed the old coolant. However i could not get the drivers side of the car to heat up. She had mentioned that the car took a long time for the cabin to heat up but it was like that the past year, The picasso still had a heater but only on the passenger side which explains why it took so long to heat up.
Initially i suspected broken heater flaps similar to a Peugoet 407:
• Peugeot 407 drivers side heater flap fix
However after plugging in the Kingbolen Ediag Plus, a device they have sent to me for review which i have not got round to finishing:
https://kingbolentool.com/products/ki...
That allowed me to see the heater flaps cycle between hot and cold, i could see they were moving fine, but for added peace of mind i removed the stepper motors and moved the flaps by hand and they moved with no resistance which ruled that out.
The thermal camera was then used to look at the system. I have a Topdon TC004 which is available from this link:
https://www.amazon.co.uk/TOPDON-Resol...
The thermal camera showed that the heater matrix was hot on the passenger side, where the coolant goes in. However, on the drives side it was cold.
With the diagnosis complete i determined that the heater matrix was the issue and ordered the replacement from ebay.
The actual replacement is not too difficult, i would advise waiting for the car to be completley cold as you can see in the video even after 30 minutes of waiting there was enough pressure in the system to cause the coolant to shoot out. Let the system fully cool and also remove the coolant reservoir cap to release any pressure. Thankfully despite the mess of the coolant escaping it was not scalding hot so i was not injured. Obviously wash your face and hands after coming into contact with coolant and do not let pets near it.
The installation of the matrix was fairly straightforward, take your time to ensure the clips are properly attached and tightened as any issues there will cause leaks between where the pipes and heater matrix meet.
After the pipes are installed the coolant is bled, i used a Lisle 24680 spill free funnel kit:
https://www.amazon.co.uk/Lisle-24680-...
Ive had that for over 10 years now, a great kit but does not have an adapter for PSA cars, i took a coolant reservoir cap off a MK1 Citroen C5 diesel and drilled a hole through it which works well. The funnel means that new coolant is at the highest level in the coolant system and the weight of the coolant in the funnel pushes out any air, so when the bleed screws are open it rushes out. There are other ways with old bottles and lots of insulating tape but i do enough work around coolant systems to find this worth having.
Once the heater matrix was in, and the coolant bled the car was allowed to run for 15 minutes and the heater felt nice and warm on both sides. It improved even more once i drove the car on the road.
The old heater matrix was cut open with an angle grinder and it was clear to see the issue, it was completely bunged up with sludge at the far end, ie the side that was serving the drivers side. This prevented it from heating that side up.
Regarding the diagnostic device used in this video it was a Kingbolen ediag plus which is available from this link:
https://www.amazon.co.uk/dp/B0CKYZKYKC/
For any further questions feel free to ask in the comments below or message the facebook page for this channel:
/ pc2cv
0:00 - Introduction
0:15 - Initial Diagnosis
2:40 - Drivers side heater flaps
5:00 - Passenger side parts
7:30 - Thermal imaging
8:20 - Heater Matrix Replacement
8:40 - New Heater Matrix
8:55 - Glovebox Removal
11:30 - Close to Heater Matrix
12:25 - Coolant Pipes
13:27 - Big Mistake
14:00 - Heater Matrix Removal
14:45 - Installing new Heater Matrix
14:10 - New o ring seals
15:30 - Connecting pipes to matrix
19:35 - Cleanup
20:10 - Bleeding Coolant
24:00 - Old Matrix Autopsy
24:52 - Reassembly
25:15 - Working Heater
#CitroenC4Picasso #HeaterMatrixReplacement #CitroenC4PicassoHeater
#CarRepairTutorial