Question about 1991 Peugeot 405

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Knocking noise from air evap unit

Car developed a knocking noise under the dash.. on further investigation it goes away when you turn on the recycled air button but returns as soon as you go back to fresh... took the glove box out and the noise is coming from the big cylinder thing whish i beleive is the air dryer?? any advice apreciated as to how to get this unit out..

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  • matt3270 Feb 16, 2009

    brill.. thanks very much..

  • Anonymous Mar 13, 2014

    I get this knocking noise when i turn the heat on. If i turn the heat down, it goes away. Any suggestions? Its a 2010 f150



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2 fixes - read on - one quick and one long and hard
(little tip - take pics (camera phone) rather than try and remember how it should all go back together)

the knocking is a motor and gears that move the fresh air/recycle flap - it is up behind the dashboard behind the glovebox
the problem is that the gears wear and become misaligned
the flap then can not open fully, its doesnt reach its end stop which switches the motor off
so the motor keeps going the and the gears keep clicking over

the big cylindrical thing you are seeing is the blower motor - it should have a red and a black wire going to it

1. quick fix first
remove the wires to the blower motor
undo the 3 brass coloured cross head screw from around the blower motor
remove the blow motor and fan
turn on the ignition and put the air flow to fresh air (i.e not recycle)
the knocking should start
lay on your back with your head i the footwell
with torch and hands locate the motor/gears that are knocking
find the wires to the motor and remove or cut them (if cutting turn the ignition off first !!!)
make sure the flap is in the open position, tape,jam or wire it open (who uses the recycle position anyway ??)

2. long hard fix
remove the blower motor as described above
this leaves the fan casing
from the engine bay remove the plastic cover from the top where the windsceen wiper motor is (just below the windscreen)
depending on model you may have the engine management CPU on the right handside - this may need removing
on the right hand side there will be 3 (maybe 4) bolts just above where the fan housing is
undo these - note i have seen these with the bolt head in side the car and some with the bolt head on the engine side - dont know why ???
if they are inside the car - you need to remove air trunking, repostion wires and get a long thin socket extension and some flexible bit to be able to get a socket on the head.

once all this is out - locate the motor/gear making the noise (as above)

remove the motor wire and after removing any more obstructing object remove the motor and gears- you will need to be very flexible and have a good range of flexi and rightangle drive socket bits

now all you need to do is purchase the new gears (if peugeot have any) rebuild it all and refit, then put everything back as you found it

shouldnt take more than a day or two, or a finger or two

Posted on Feb 14, 2009


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