Luke warm air instead of hot air

[Mark_B]

Here's an interesting one. The delanair mk3 climate control all seems to be working correctly, but the heat output from vents is luke warm only. The car interior takes a long time to heat up, and there is lots of air blowing out the vents but not really warm enough. Other symptom is when the engine is ticking over in traffic, the air becomes even cooler, then when the engine is revved the air warms slightly. Another thing that happens is if the climate control is switched completely off for a few minutes, then back on, the air from vents is quite nice & warm, but it cools down rapidly.

Now by those symptoms you'd think: 'ah!.. partly blocked heater matrix'.., so you feel the inlet and outlet water pipes, expecting them very different in temperature, and then you are puzzled because they are both as hot as each other. That means there is no partial blockage at all in the matrix, or anywhere else, what's more this proves the very hot water is passing freely through the heater. So then you think, 'ah.. it must be blocked airflow then'. But then how could it be?, because there is plenty of air coming through, it's just luke warm.

Well here it is: The inlet and outlet pipes are attached to the same side of the heater matrix end piece. Inside it, a baffle plate between these pipes forces the water to flow around the matrix. What's happened is the baffle has dropped out of position, allowing the water to flow the very short route between the in and out pipes, rather than through the matrix.

The heater matrix on delanair mk3 can be replaced without removing the dashboard.

[Patfallon]

thanks for that. i don't need the info yet but you never know, one day I might