1999 Audi A4 noisey heater

AUDIVALAND

MEMBER
1999 AUDI A4
4 CYL
2WD
MANUAL
90,000 MILES

Hello

I have the above mentioned vehicle which runs on petrol and when I turn on the heater in non-econ mode it starts knocking in the engine compartment sounds a bit like a diesel black cab. I am getting tonnes of suggestions like it is the heater blower motor or it is th air con compressor or its the clutch on the A/C compressor. I am confused. When heater is switched on in econ mode the problem resolves. The problem exists with hot and cold engine.

3 Replies

RACEFAN966

MECHANIC
5,029 POSTS

Ok so when you turn the heat on and blower on high when does it make noise? Does it make noise on defrost? If you turn it to floor or vent does it make noise then? How car savy are you? I ask because what I need to know is if the noise only comes on when you have it on a setting that causes the A/C compressor to come on or not?

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Saturday, February 14th, 2009 AT 1:20 PM

AUDIVALAND

MEMBER
2 POSTS

Hello thanks for your prompt reply, Heater fan setiing i.E hi or low both makes noise, Makes the noise if fans are up to windscreen, down to feet, or centre and side dash. Recirc makes noise as does demist or defrost setting the only setting that stops noise is by pressing econ mode with any of the above. I am thinking clutch mechanism on A/C compressor is not moving adequately to required positions. What do you think. Forgive my guesswork I am an amateur at this stage.

Kind Regards

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Saturday, February 14th, 2009 AT 2:47 PM

RACEFAN966

MECHANIC
5,029 POSTS

Ok here is a pic of the A/C compressor the front of it has a clutch that engages with an electro magnet and that causes it to turn. So the question is does it turn on econo setting or not. If it doesn't turn in econo mode but does in all the other possitions then yes I would say the a/c compressor is bad. Let me know what you find.