flushing heater matrix

[bmw9818]

think i may have a blocked matrix, assuming once the valve is open water should flow freely in & out the stub if i were to put a hose to it right?

is the heater valve electric or manual btw? thanks

[DanThe]

Yes it should flow through
The valve is electronic, you will see the plug/wires at the top when looking at it from the passenger side footwell, with the ignition on when you turn the heater dial from cold to hot you should be able to hear it opening and closing

[bmw9818]

had a look the valve looks like it has been leaking a bit theres some patches sings of leakage and the top is corroded green and the surrounding brown rusty water, so prob needs changing

Had a power issue as well i checked the plug going to the valve just to rule it out, i wasnt getting any 12v at all i traced it back and found a small inline 2amp fuse which didnt look blown but had no continuity so changed it with smalllest i had a 5amp...

i got 12v but only on fully cold, after i moved it slightly off it dropped back down to 0 volts ish should it not drop down to 6v etc then to 0 only when fully turned to red?

and coudnt hear the valve make any noise at all so assuming its seized up

[BenHar]

The valve only uses power when set to full cold.

Yours sounds correct.

But the diaphragm inside has probably disintegrated.

Common fix is to use o-rings to replace the diaphragm. This means that it won't fully shut off but the amount of heat that gets through is negligible.

Ben

[bmw9818]

managed to pull it off alright, just drilled out the rivets and cleaned the plunger up and started working okay, bunged some sealant around and refitted hopefully that should be okay for leaks

[Brianmoooore]

i got 12v but only on fully cold, after i moved it slightly off it dropped back down to 0 volts ish should it not drop down to 6v etc then to 0 only when fully turned to red?

You'd only get an intermediate voltage if your car has the very rare option of climate control. In all others, the valve is only used to ensure 'cold' is completely cold.

If flushing the matrix with a hose, it's important to connect it to the lower stub pipe in the cabin. Connecting a pressure hose to the top stub is likely to damage the electric valve.

[bmw9818]

Ah right didnt know that! Always thought i had a fault with my heater knob or something as it was always fully hot or cold,

but yeah sorted managed to bleed it up about 3hrs and a shit load of water later! Always such a headache bleeding these