451 Heater Blend Flap Motor

Clicketty Click Click Click Click

Car’s on, you adjust the temperature and you get lots of plastic clicking noises and then silence. It’s usually because something has got into the cabin heater box and has blocked the heater blend flap. The motor tries its best and eventually strips the teeth of the internal gears.

Luckily, it’s easy to get to. Look in the right hand footwell, over towards the centre.

Remove the 3x Torx 15 screws and you can pull the motor off.

Disconnect the electrical connector and you have it removed.

Fix Or Replace?

With the motor off, see if the recirculation flap moves freely and isn’t being hindered. There’s no point doing all of the work if the issue that caused the problem still remains. If it moves ok, great.

The noise you are hearing is damaged/stripped gears inside the unit. You could try opening the unit but you can’t buy the gears separately.

Opening

This is the actuator unit. It’s the same unit that is also used to move the heater blend flap.

It’s nothing special and they are used in VW, Audi and Skodas.

5 pins and double check the warding on the connector if you are looking to buy a non smart one.

They are clipped together all around.

Just lever and pull all the way around…

…until the top comes off. Now you can see the 3 cogs. This unit is ok and all of the gears are intact.

Alessandro T had the clicking noise from his unit. As you can see, the small yellow gear has lost some teeth.

These are the 2 cogs that fail although it’s usually the yellow one.

Because there’s no way to get the gears separately, I decided to model them so people can try 3D printing their own. A site viewer called Christoffer S helped me fix the 5 degree angle on the yellow gear’s teeth.

Download

Your crappy 10 year old 3D FDM printer is unlikely to do a good job printing these. Ideally it needs to be printed in nylon. SLS printing is probably your best option.

I would like to point out that I haven’t even tested these. Feel free to have a go and test them yourself. Let me know how you get on. I do not give you permission to print and sell them, they are for personal use only.

Click here – Tinkercad

Replace For New?

Contact smart and see if they still sell the unit. The part number is A4518290001. Get the price and then look on eBay for 2nd hand ones. Just in case someone is selling a 2nd hand one cheaper than a new one. (again, unlikely).

Alignment

If you fit a replacement or are having issues with getting hot or cold from the vents, you can run a “teach in” procedure on MB Star DAS.

N23 Heater Air Conditioning Operating Unit.

Actuations.

Teach In Component M16/8 Blending Air Flap Actuator.

Click start and very quickly you should see the teach-in process was successful.

However…

When I ran this, it also calibrated the position of the recirc flap (M39 Recirculated Air Flap Actuator Motor).