Thread: knock sounds when switch on/off heating 【A4 B7 1.9TDI】

hi everyone. My car recently having few knock sounds every time i switch on/off the heating. Anyone can give some advice what's that? thanks in advance

Maybe the flap closing, try it in E mode. Does it only do it when the recircluating button is on?

the sounds happens :

every time i turn on/off the key, i mean give the power to the car electric device,but not turn on the engine. doesn't matter the heating is on or off.
every time i turn on/off the recircluating button
every time i switch on/off the heating, i mean the "OFF" button.

but the the knock sounds from "turn on" is different from the sounds from "turn off". sounds like something knocked from two different way.

If the knock is coming from under the dash it could be one of the air distribution flaps sticking - I had this a few months ago and was able to diagnose which motor using VCDS (VAG-COM). On investigation I found that the motor was OK but the operating lever had jammed.

was on motoway this morning, and it's raining. so i've also found i could hear the same noices as soon i use liquid screen wash, and every time

Originally Posted by PetrolDave

If the knock is coming from under the dash it could be one of the air distribution flaps sticking - I had this a few months ago and was able to diagnose which motor using VCDS (VAG-COM). On investigation I found that the motor was OK but the operating lever had jammed.

thanks for the experience.but is there anything should be replaced in this case?

Originally Posted by sidibear

Maybe the flap closing, try it in E mode. Does it only do it when the recircluating button is on?

E mode doens't make any different,but no noices from switch on/off the E mode

Dave,

how did you cure this what methods were used to un jam!!!!! as mine doing the same and wont de -mist windscreen help!! Vag says flapp jamed....

Originally Posted by PetrolDave

If the knock is coming from under the dash it could be one of the air distribution flaps sticking - I had this a few months ago and was able to diagnose which motor using VCDS (VAG-COM). On investigation I found that the motor was OK but the operating lever had jammed.

Problem found with the air recirculation motor, My part number is : 8E2.820.511D. Made in Spain

i can't find the exactly same one on ebay. will phone the dealer on Monday

Originally Posted by Rock

Problem found with the air recirculation motor,

Ahem, cough.

Originally Posted by sidibear

Maybe the flap closing, try it in E mode. Does it only do it when the recircluating button is on?

Originally Posted by V6 Quatt

Dave,

how did you cure this what methods were used to un jam!!!!! as mine doing the same and wont de -mist windscreen help!! Vag says flapp jamed....

Removed the motor (3 screws IIRC) and separated it from the mechanism which I checked was free to move by hand and then refitted the motor to the mechanism. That's all I had to do.