C3 Picasso heater only blows cold.

[mart]

Hello. I'm normally used to giving and receiving help on Hot Rod forums, but this is my "daily driver" 2010 C3 Picasso 1.6 Diesel.
It is a lower spec model and has relatively simple heater controls. As the weather has gone colder I am now aware of the heater only putting out ambient temperature air. I have looked online quite extensively and not found anything specific to my problem. I had it running and it seems the engine never really gets particularly hot. I can have it idling on the drive and the radiator stays virtually stone cold. Thinking the thermostat might be stuck open I bought a replacement and fitted that. It made no difference at all. I have topped up the filler tank and bled the fittings on the heater elbow and thermostat housing. After 30 minutes idling on the drive the engine end of the top hose is just barely warm. The radiator is not warm at all. I can hear things making different noises when I operate the heater controls, no clicking noises indicating broken parts.
I should add that the car does not tend to overheat.
Having exhausted what I can do "easily" (the thermostat housing was not a walk in the park) I am faced with invasive surgery in towards the heater box itself.
So my questions are:
Can anyone say if they have encountered a similar scenario?
Will a diesel open the thermostat on a cold day?
Would my car have stepper motors on the heater?
Is there anything on the heater I can manually jam open to make it produce hot air?
Where is the stepper motor positioned for the hot cold mix flap?
Is there a part number for this specific stepper motor?
How would I get access to it (what needs to come out)?
Could it be the heater temp selector knob at fault?
I'm quite capable but have never worked on anything as new as this.
I can't believe how difficult these modern cars are to work on.
I have seen links to videos for c3 and c4 picasso. Is the c3 picasso similar?

Thanks very much. I hope I can get some good advice.

Cheers. Mart.

[GiveMeABreak]

When was the coolant last flushed? It may be a blocked heater matrix that restricting water flow.

[mart]

Hello Marc.
It has never been flushed in my ownership. Is that a thing?? (Lol) Probably never. The coolant doesn't seem particularly murky. Do you think I could flush it by accessing the fittings at the bulkhead?

[GiveMeABreak]

Some have attempted to back flush it with a hosepipe - where the matrix connectors enter the bulkhead, but no guarantees.

[CitroJim]

The HDi engine has always been a cool runner. It comes from its great efficiency and the early first-generation ones were so 'bad' I could drive my 2.0 HDi Xantia 6 miles to work without the thermostat opening on a cold day. Some had auxiliary heaters fitted, either electric or diesel, to give quicker cabin heat, so bad was the issue.

Idling on a cold day, the engine will never get hot enough to open the thermostat and flow through the rad... So what you see is to be expected.

However, that should not stop the heater matrix warming as coolant will circulate through it always, irrespective of the thermostat. When under way there should be plenty of hot coolant for the matrix even if the main rad is stone-cold.

Take it for a run and feel the hoses going to and from the matrix. They should be hot. If they are, then coolant is flowing through it. It's rare to have a blocked one, especially if the coolant looks OK.

If the hoses to the matrix are stone-cold then most likely you have an air-lock and another bleed should fix it.

For the record, my 1.6 HDi C3 Picasso warms up quite rapidly on the coldest of days and cabin heat is available after about half a mile.

If all else fails then you'll have an internal heater problem or a control problem. It might be a good idea to run Diagbox diagnostics across it to see if the heater is reporting any issues...

[GiveMeABreak]

Engine Temperature on my 1.5 HDi Aircross reaches normal operating temp. of 90°C on the dial within 4-5 miles.

[mart]

Thanks for the pointers. I will have a look at applying a hosepipe to the matrix connectors. I will report back if and when I have some news. Thanks again.

Mart.

[mart]

Hello. Today I was able to try flushing the heater matrix. I accessed both pipes where they connect to the engine. I was able to apply the tapered nozzle of the garden hose to both hoses and observed water flowing through both ways. Initially disappointed, I did observe what I would describe as quite a bit of back pressure. I continued to flush first one way then the other and I don't know if I am fooling myself but I thought the flow increased and the backpressure reduced. Anyway I reassembled it all and bled it out.
Well I am pleased to report that there is now some warm air coming from the heater. Not a lot, but certainly more than I had before. I always remember the heater in this car not being very good so having something now is definitely a big improvement.

Thanks very much for the helpful suggestion. I have now become a dab hand at removing the battery and trunking to get access to the area concerned.

Thanks again.

Mart.

[CitroJim]

Good work Mart

[CitroJim]

Sorry, I didn't complete my reply... Did you feel the pipes going in and out of the matrix to see how hot they were after a decent run?

I know they're hard to reach but only in this way will you know if it's a matrix flow problem or a flap movement problem in the heater box causing your lack of heat.

Mine roasted me on my return home from a cold, wet and muddy run yesterday!