2017 Berlingo 1.6hdi cold air via heater/overheating issue

[stu76]

Hi all.

I am needing some help/advice here please.
I have a 2017 1.6hdi berlingo with the following issue.
It started to overheat and go into the red all of a sudden when driving, anyway got recovered via the AA, he thought it might be the temp sensor or thermostat, he tried to take some bits apart at the roadside but said it was too involved so got revovered back home.
Anyway this model has the lovely all in one built in thermostat housing with all the temp sensor etc all built in and is all electronic.
Anyway I have replaced this unit, hell of a job very fiddly to do, Upon this I am not getting any heat within the cabin when its on max hot heat only cold air! I have undone both bleed nipples one at the thermostat housing side and one at the back of the engine bay connected to the heater matrix, bled both and all is fine with constant flow, no air bubbles, get van upto normal operating temps around 85/90 o/c and still cold air blowing in via the heater into the cabin! appears to not be over heating.
Anyone know any solution to this as I have been working on this van this whole weekend and assumed by changing the thermostat housing this would have just sorted out the engine over heat issue, well that has but the cold air issue is annoying, I have even flushed the heater manifold, water flows in and out of it fine, I can only assume its a faulty unit I have purchased? or does these electronic thermostat modules have to be programmed to the van via the ecu diagnostic machine.
Can anyone please help? much appreciated.
Thanks a million if you can help/advise please.
Stu.