C4 Picasso 2015 (B78 plate) Heating problems

[Hell Razor5543]

Be aware that Valeo (who make a lot of OEM parts) have, in the past, stated that, should you replace a heater matrix (OK, this is on a Xantia) you must use Forté Stop Leak (to seal any micro leaks) for their warranty to be valid. This is safe to use on Xantia (I cannot speak for other Citroens), even the V6 with the oil cooler for the gearbox (others do cause problems for that oil cooler).

[Chris570]

Just to add to this, I have the same year of car and I STRONGLY suspect a blocked heater matrix (as it was for the original poster). Citroen actually changed the matrix for this car in later years so it may be a known fault.

I'll be pulling my matrix soon to confirm if it's blocked or not (my flaps are moving as they should as well as it goes from ICE cold to cold)

I agree though that earlier cars are well known for broken flaps so never say never!

As a follow up, I finally got round to pulling my matrix (20 min job, far easier than the Xantia!)

I poured boiling water in one end and only about 15% of the matrix got hot! Its only the passengers side that gets hot which explains it.

There was a LOT of sediment in there, I've tried flushing and back washing and lots has come out BUT still the whole thing isn't heating up as it should, I think the galleries are very small and prone to blocking.

What's come out looks like red brick dust so I'm not sure what's caused it.

Anyway I think it's worth noting that on this car the matrix is quite likely to be the problem when you've got cold air on the RHS

[Chris570]

VF7**************[VIN obfuscated, can be read by forum staff]

Would someone be so kind as to provide me with the part number for the heater matrix for this? I'd rather fit a new one if possible than clean the old one out

[Molsonwill]

Hi everyone, I have a 14 plate diesel picasso with the same issue, I was about to order a new matrix but then tested the electric matrix which works fine. However when the engine is started from cold the left side warms up quickly with the driver side still cold. I would assume that this rules out the matrix. Thoughts!

[Molsonwill]

If I could add to the last question, there is an elongated hole in the heater box just below where the pollen filters go in, I'm getting cold air blowing out of it. I'm sure that this shouldn't be the case, if anyone could throw any light on this. Thanks.

[GiveMeABreak]

This topic has been covered lots of times, but in summary, it can either be the temperature mixing motors or flap spindles, or if not these then it's possible that there is crud or a blockage in the matrix which is why you are only getting the heat from one side. If the coolant has been drained and refilled at anytime, it is important that it has been done correctly and bled / degassed to avoid blockages / locks.

[Molsonwill]

Thanks for that marc. I can't help but think that when the engine is cold, the electric matrix would warm both sides before the matrix came into play. I have all the plastics off and you can see the flaps moving so there's no motor or spindle issue. I have to block the hole under the filter door to stop cold air blowing in directly. This shouldn't be the case and I can't help but think it's directly related.

[GiveMeABreak]

When you say the 'Electric Matrix' - I assume you are referring to the Air Heating Resistors for the passenger cabin? These will only aid in helping get a little heated air into the cabin and are mainly used as an aid to demisting the front windscreen so I wouldn't expect the equivalence of a fan heater

Pop up your VIN for me so I can see what system you have (VIN is Auto Masked on submission) and it might help me to see what hole this could be.

That 'elongated' hole you are referring to may simply be the footwell ducting:

[Nimah]

Hi everyone,
I brought a 16 plate citroen grand picasso and the heating on the drivers side doesnt work ( it blows out cold air when outside was freezing). How much does it cost to investigate and fix the issue?

Kind regards,
Nima

[xantia_v6]

What is the substance that it clogs with?

[GiveMeABreak]

Scale, rust, improper use of sealant products etc. Blocking wouldn't be on my priority list for such a recent car - unless it has been drained and refilled with the wrong coolant or an incorrect mixture and has started to rust or has a lock in the system.

[Molsonwill]

hi marc, this is a link to an image of the heater box and the hole i was talking about emitting cold air. i'd just like to understand what this is before dismantling further . vin number is VF7**************[VIN obfuscated, can be read by forum staff]
there is nothing to go on it and the floor heater duct is above. there is no matching hole on the n/s.
I don't know if this is the correct way to post an image. Will.

[GiveMeABreak]

I'm afraid I can't identify that from the picture and the available info I have which is of the other side, but it looks like a fixing for one of the ducts. Bear in mind that the heater units are the same for left and right hand drive vehicles with one heater duct different depending on LHD / RHD.

[Molsonwill]

Just pulled the matrix and of course its blocked. its nice to find a positive fault. The cold air blowing out of the small hole has just been throwing me. I'll try and get a look at another airbox. If the new matrix sorts it I'll just have to leave the hole stuffed with a piece of rag. i just don't like a mystery. Thanks for the help and I'll post the results of the new matrix next week. Will.

[RichardW]

It's possibly supposed to be plugged - item 9 below

It is £17.50 though.... I'd be tempted to stick some duct tape over it!

Bad news on the matrix.... at least it's not too hard to get out!!