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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22154
Experience:  BEng hons Mech engineering, in auto industry 22 years
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The heater on my 2.9 diesel Sedona has stopped working. Ive

Customer Question

The heater on my 2.9 diesel Sedona has stopped working. I've checked my coolant level thinking I might have a leak but it remains at the same level. My next thought was the thermostat which I have taken out but its made no difference. I can only travel around 5 to 10 miles before the temp gauge starts to climb above its normal running position
Submitted: 3 years ago.
Category: Car
Expert:  Matt replied 3 years ago.
Hello


I'd start by fitting a new thermostat as its needed to control the flow around the engine and it sounds like the cooling system may not be in good shape if its overheating and yet you have no heat?


Whilst the thermostat is being replaced you might as well also reverse flush the cooling circuit (remove top hose to rad and use a hosepipe to push water into the engine until you get clear water out of the radiator hose) and top up with 30-50% fresh antifreeze. Also check that the small diameter bleed hoses that run from the top of the radiator and the top of the engine aren't blocked as this allow the air to vent back to the header tank automatically.

then have a feel of the two coolant pipes that pass into the car through the engine bay bulkhead, both should be warm with a warm engine. If they're not then its likely the heater matrix is blocked and you should do a reverse flush on the cooling system to try and clean it out. This is done by removing the top hose from the radiator and placing a garden hose into the engine water outlet, and then run the hose until you get clean water coming out of the radiator.

If this doesn't help this only leaves checking out the motor / cable that move the air mixing flap that allows the hot air from the matrix to enter the car air system.

This flap is controlled by the temperature knob / dial etc and I think is controlled with a small motor for your car so the thing to do is first get access to the back of the control knob and measure the voltages is present there, then trace the wiring back into the dash from the control to locate the motor.

It’s worth first checking the fuses for the fan / control circuit

I'd recommend first removing the glovebox ( undo lower edge hinges from dash) to gain access to the dashboard inner and also allow you to shine a torch to the back of the central console so you can start tracing the wire back and see how things are put together