W210 whistling dash pods
 

Yes I searched. I think my issue is too specific for the threads I found.

Whistling from HVAC only when A/C is invoked. If I hit EC it goes away. If it's cold outside and heat is being invoked it goes away. But when the set temp is reached and the HVAC goes into maintenance mode it comes back. It is LOUD and can be continuous, uninterrupted whining/whistling noise while driving.

I suspect it is an A/C blend flap vacuum pod. I know the sound of a vacuum pod, I already replaced one on this car a few years back to solve a very similar noise.

I've removed glove box and passenger under-dash and tunnel panels. Removed vacuum line from each accessible pod and plugged, none of which made the whistling go away. I believe there is another pod that I can't see (?) possibly behind the radio? It sounds like it's coming from in there.

Any ideas?

Whistling with the AC engaged on the W210 is a common symptom of low refrigerant. I'd first check that before I started digging in elsewhere.

The facelift 210 allows you to run some HVAC diagnostics (including system pressure) from the climate control itself. Still, if you're considering adding refrigerant, I'd use a gauge set to first determine the pressures and, of course, to add some if needed.

Good luck.

Not a low refrigerant issue - the charge is perfect. I check it every year. Also, I now notice the whistling regularly occurs with the EC activated as well (conclusively rules out refrigerant issue).

I did the air flap self-diagnostic test: 220695 c question mb w210 ac diagnostics flap test pdf free ebook download from mbworld.org

The whistling occurs with DTC 3. This points to the pod for "Left Blend Air Flap". Can someone tell me where this pod is? If it's on the driver's side as I suspect, then the dash may indeed need to come out.

Does someone have a diagram of all the pods and their locations?

Answer
 

http://i21.photobucket.com/albums/b2...ps531132d1.jpg


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W210 whistling dash pods
 

Thanks whiners, looks like its probably 53, that's one I didn't check. Do you know if it can be accessed without dash removal? Perhaps from driver's footwell?

W210 whistling dash pods
 

Sorry, autocorrect. I meant whunter. Not whiners!

Answer
 

You access it from driver's foot well. :)


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Thanks for this awesome, helpful info!

I pulled the suspect pod and took it apart (it was indeed #53). It had 2 holes in the diaphragm from all those years of flexing. One hole was pretty big and had a trail of black grit leading to it; I suspect it had been leaking for some time. The second hole was a newer one, and more of a "slit." I think this was the one that was whistling.

I ordered a new one from the dealer this morning, $103 and change.

Thanks again for this info, the car was nearly undriveable with that LOUD whistle going nonstop!

Question
 

Glad to help.

Could you estimate how long this DIY would have taken, if the new part had been there?



Thanks.

W210 whistling dash pods
 

20 mins if part was in hand. Easy once you provided me with the info. The hard part was troubleshooting and narrowing it down to 53. The link above with the flap tests is extremely helpful.

My 99 e320 has a right center vent pod that is whistling. I can see the top of the pod and the rod connected to it from the glove compartment opening. I can see the bottom of the pod and the vacuum line attached to it after removing the bottom panel. Can this pod be replaced without removing the dash? If so, how do I do it?