1997 Mercedes Benz 280 intermittent whistling noise when CL

Tiny
PHIL WALDO
  • MEMBER
  • 1997 MERCEDES BENZ 280
Noises problem
1997 Mercedes Benz 280 6 cyl Two Wheel Drive Automatic

There is an intermittent high-pitched whistle when the heat/AC is in use. It occurs most often during light acceleration and cruising speeds. It stops for a short period of time when acceleration is decreased.
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Thursday, January 15th, 2009 AT 3:00 PM

4 Replies

Tiny
IMPALASS
  • EXPERT
Hello -

On one of the TSB, Heater Blower is Noisy; it states the air intake below the windshield is obstructed by leaves etc.

There is another one, Knocking/Humming Noise at idle with A/C on.....I have attached the info on it.

I would also check the cabin air filter and replace it. I have attached that for you as well.

If you haven't every changed this.....you would be surprise how much debris can be in there.

I would look at the air intake area and clean that out really good. Then remove the blower and clean all of that area out and then the filter and see if that makes a difference. If not then check into the other TSB.

Cabin Air filter


http://www.2carpros.com/forum/automotive_pictures/248015_1_158.jpg

]

2 Cover
3 Clip


http://www.2carpros.com/forum/automotive_pictures/248015_2_106.jpg



1 Dust filter

Removal and Installation :

Remove cover panel below instrument panel. See: Body and Frame Interior Moulding / Trim Dashboard / Instrument Panel Service and Repair
Take off cover (2). Push the two remaining clips (3) in the direction of arrow for this purpose.
Pull dust filter (1) down and out (arrows).
Install in reverse order.

Knocking/Humming Noise at Idle With A/C On

All Technical Service Bulletins


http://www.2carpros.com/forum/automotive_pictures/248015_3_74.jpg




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http://www.2carpros.com/forum/automotive_pictures/248015_9_10.jpg

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Thursday, January 15th, 2009 AT 5:50 PM
Tiny
PHIL WALDO
  • MEMBER
>The system filter is clean. The vent covers that supply the air for the fan are clear. There is no restriction on fan delivery.
>
> This noise sounds more like a vacuum leak. It does not occur continuosly. It does not occur when the climate control system is off. It does not occur when the engine is coasting (not accelerating). It occurs intermittently during most trips. But, there are trips when it does not occur at all.
>
> There is a vacuum line that penetrates the firewall below the coolant hoses and control module on the passenger side. Is there a vacuum module in the heater/blower area that affects some function of the climate control? If so, how do I access it?
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Friday, January 16th, 2009 AT 1:48 AM
Tiny
IMPALASS
  • EXPERT
Hello -

I think this is what you are asking for. I have attached vacuum routing for the climate control. What you may be talking about is near item 35....I think this is where it comes through the firewall. I would start at 36 and work my way into the car.


http://www.2carpros.com/forum/automotive_pictures/248015_1997_MB_1.jpg



35 Cockpit separation point
36 Vacuum valve block
38 Vacuum element for defroster outlet flaps
39 Vacuum element for footwell flaps
41 Vacuum element for center nozzle diverter flap
44 Vacuum element for fresh/recirculated air flap
45 Vacuum element for left center nozzle blend flap
46 Vacuum element for right center nozzle blend flap
Y11/3 Switchover valve block (8 connections)

Color Code :

bl = blue
hbl = light blue
drt = dark red
ge = yellow
mgn = medium green
gr = gray
rt = red
ws = white
sw = black
dgn = dark green
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+1
Friday, January 16th, 2009 AT 5:11 PM
Tiny
IMPALASS
  • EXPERT
Hey also, it looks like you may have some recalls on your vehicle. The dealer may fix these for free. Please contact the dealer service department, give them the VIN number of your car and have them check on these to see if they apply to you. I would check these out also.

1999080001
12/01/1999
Recall - Infant Restraint/Booster Seat Exchange

NHTSA99E024000
08/02/1996
Recall 99E024000: Child Restraint & Booster Seat Defect
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Friday, January 16th, 2009 AT 6:57 PM

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