Bizarre Renault Megane prob, help?

[CreepingJesus]

I've got an odd problem with the Megane. It's not serious, but it's bloody annoying.

When it's all cold, like when I go out to it in the morning, there's a knocking noise from under the dashboard when I shut the door. It's quite an audible sound, neither metallic nor plastic sounding, just kinda 'solid' if you get what I mean.

It usually knocks about 5 or 6 times, quite rhythmically, as if it were sprung, or on a pendulum. With the ignition set to 'electrics' or with the engine started, it knocks a couple more times. Once everything's running it isn't heard again.

I'm sure the noise comes from in front of the passenger's seat, but I've looked under the dashboard, and under the scuttle panels as best I can. I can't even see a component which could be making a noise like this. Just for once, I'm completely stumped.

The old Megs are fairly common cars, has anyone here had a similar problem? Help please?

[greengartside]

Just been browsing Google and it mentions something about the air recirc flap sticking or malfunctioning? Seems like it's under the passenger side scuttle panel area? I know you have said you have looked at the scuttle panel area but this is a common prob on these apparently. Try and disconnect/block it up and see what happens.

[meggersdog]

Yep what greengartside says.

Look through the mesh of the heater air intake under the bonnet.You should see the flap moving up then slamming down again half way through it's cycle.That will be the noise.

[Formula Autos]

Stereo connectors are sometimes quite hefty bits of plastic and might produce a knock like this. Worth whipping the head unit out for a look behind?

[CreepingJesus]

Thanks for that, one and all. The heater flap sounds quite likely, actually, and I wouldn't have been looking in the right place would I?. I'll check it out tomorrow.

Altho', I'm not ruling out the connectors idea either, 'cos the head unit falls out from time to time. So gawd only knows what's going on back there. (The spare DIN cage which came with it may be a clue... )

[Renault18]

It's almost certainly the heater flap. I've done a couple now. It only affects the aircon models as it's the flap that operates the air recirculation. The motor spins when you switch on and when you alter the setting from normal airflow to recirculation. If the flap is not held by the cog from the motor, it will bang about when the air inside the car is disturbed.

 

There are two fixes - keep on operating the sytem until the flap is jammed open, then remove the wiring plug. To do this undo the plastic half of the scuttle on the left of the screen, take out the plastic cover and disconnect the wiiring (the smaller plug - NOT the larger one, as this is for the fan) This will mean there's no recirculation - OR no normal mode - it's

hit and miss as you have to recognise the difference in sound the system makes! - and if the flap isn't supported it will still bang about!

 

The second method is to remove the entire heaterbox from out of the scuttle area and fix it. This means disconnecting the aircon. There's a way of doing that quite easily and potentially quite dangerously and probably illegally.

The job of removing the unit isn't that bad - you can then replace the parts or properly seal the flap shut or glue it open.

 

Alternatively - earplugs

[Rocket88]

I had [still have] a festering old Volvo 740 estate that does something similar, but at random intervals, can be quite alarming.That, and the stereo's prediliction for randomly turning itself up to full volume.............it's like driving a haunted bloody house.