Peugeot 407 heater unit problem. Flaps are OK

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markus_cs2002
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Joined: 29 Sep 2020, 18:52

Peugeot 407 heater unit problem. Flaps are OK

Post by markus_cs2002 »

Hi guys
This is my first post here and hope i can get some help diagnosing the broken heater unit on my Peugeot 407.
The passenger side is always blowing cold while driver the side is stuck on hot.

I know that this is a very common issue with this car and flaps repair instructions can be found all around the internet buy my flaps seem good.
I've removed dashboard top plastic to get a clear view of the flaps and got surprised that both flaps are in perfect shape.
I've tried to change temperature from max cold to max hot on the climate control unit and found that flaps move perfectly fine..
Spent some time testing different air temperatures and air directions and flaps just works ...both left and right move almost the same position.

Does anyone know what can cause this weird issue.
Reading the internet many peoples experience exact issue but all the solutions claim that broken flaps are root cause.
In my case its not true.
I can make video of the flaps moving tomorrow if needed.
Thanks.

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GiveMeABreak
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Re: Peugeot 407 heater unit problem. Flaps are OK

Post by GiveMeABreak »

There are stepper motors for both the air mixing and the air distribution.

Depending on the model (there were 2 systems fitted to the 407) although the motors may be working, are you sure you can see the actual flaps moving? These would appear to be internal to the unit and it is often the motors that do not fail, but the spindles further inside that snap off or are freely turning.

If you are sure it is not these, then it could be 2 further issues:

1) Low refrigerant. If the refrigerant level is low, there won't be enough cool liquid getting through the other side of the matrix before it turns back into a gas, so is only effectively cooling on one side as it enters the matrix.

2) If the refrigerant has been topped up, the matrix may be clogged up, which will also cause the same symptoms as above - a restriction in the matrix will result in poor circulation and the liquid will start reverting back to a low pressure gas, thus loosing it's cooling ability as it returns back to the compressor.

markus_cs2002
Posts: 2
Joined: 29 Sep 2020, 18:52

Re: Peugeot 407 heater unit problem. Flaps are OK

Post by markus_cs2002 »

Hi GiveMeABreak.
Thanks for the quick reply.
You where absolutely right about the flaps....i was looking at the wrong ones.
The correct flaps are located just beneath the the flaps i was looking at. And yes they are broken.
Luckily they are reachable from the top and perhaps can be fixed with epoxy resin without disassembling / cutting the side plastic.

If anyone interested in this fixing method please have a look at this video:



I did it already just need to wait 24h for the epoxy to fully cure.
I will post the final results here.
Thanks again.

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GiveMeABreak
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Re: Peugeot 407 heater unit problem. Flaps are OK

Post by GiveMeABreak »

Great, best of luck and at least it wasn't the matrix!!