Heated window interferes with radio

S500 Pete

Senior Member
Joined
Mar 9, 2009
Messages
788
Reaction score
277
Location
Essex
Your Mercedes
S500 (W222) 2014. Turbo 4.7 V8 with loads of toys. Superfast luxury.
Hi,

Misty mornings lately and I've noticed that when I use the heated rear window on my E500 the radio (Command unit) just turns in to a big hiss. I guess that there is a capacitor or similar somewhere between the aerial and the heater wiring that has failed.

Any idea if this is the likely solution

How much and how hard to fix?

I have a bit of the Merc used car warranty left, would this be covered?
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
I am sending you the test for the rear window
 

brandwooddixon

Senior Member
Joined
Jul 31, 2006
Messages
3,862
Reaction score
681
Location
Wolverhampton
Your Mercedes
S63 Coupe 2014
There's an amplifier behind the offside C pillar trim (same side as the wiring disappears into) that can fail.

Unless you have folding rear seats you'll need to remove the seat back to remove the pillar trim if you look at replacing it.

I think that it costs about £20 if my memory serves me right.
 

bigasotonuk

Senior Member
Joined
Nov 14, 2006
Messages
5,331
Reaction score
58
Age
56
Location
Southampton UK
Your Mercedes
C43/55 AMG 1999 / C230K 1997
There's an amplifier behind the offside C pillar trim (same side as the wiring disappears into) that can fail.

Unless you have folding rear seats you'll need to remove the seat back to remove the pillar trim if you look at replacing it.

I think that it costs about £20 if my memory serves me right.

Hi,
This amplifier I believe is generic across many models of MB with the aeriel in the rear window, and I have recently got a quote for one of £34 not sure if theres VAT to pay on that.
You will have to remove the internal 'C' piller trim on the passenger side to expose this amplifier, but it is only plug and play.
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
But the amp has nothing to do with the rear window, if FM is good when the window is not on it would not be the amp.

The info that I have sent shows how to connect a lamp in place of the window to test
 

brandwooddixon

Senior Member
Joined
Jul 31, 2006
Messages
3,862
Reaction score
681
Location
Wolverhampton
Your Mercedes
S63 Coupe 2014
So the amp doesn't do any filtering on the signal?
I didn't know that.

Or is the problem more to do with the supply to the heater?
 

bigasotonuk

Senior Member
Joined
Nov 14, 2006
Messages
5,331
Reaction score
58
Age
56
Location
Southampton UK
Your Mercedes
C43/55 AMG 1999 / C230K 1997
Hi,
The amplifier has a power supply and there is a smoothing capacitior in the same area though I "think" this cap is on the window heater supply, so it maybe a faulty cap on the window heater supply causing inerferance to the radio, possibility?
I have recently noticed a degedation in sound quality on radio in my C43, which seemed to coincide with me fitting a Parrott Bluetooth kit, I have put this down to a possible broken centre pin in the aeriel connector at the stereo, due to being plugged/unplugged a good few times and to be a known fault, I have bought a new aeriel lead from MB, this will replace the aeriel lead from the head unit to the aeriel Amplifier behind the "C" piller trim.
Please post back on what you find as it may assist me in my diagnosis.
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
So the amp doesn't do any filtering on the signal?
I didn't know that.

Or is the problem more to do with the supply to the heater?

Our cars have to have an antenna amp as they are wired in 50 ohm cable and the signal needs to be pushed through via the amp, or they would be too weak.

The rear screen contains the antenna and the heated part. As the heated part is only a conductive film, it can set up arcing that feeds back into other components. Yes some cars do have a 15.000 mfd cap to suppress the crackle, that must be fitted as near as possible to the source on interference.

This type of interference is very spiky and difficult
 
OP
S500 Pete

S500 Pete

Senior Member
Joined
Mar 9, 2009
Messages
788
Reaction score
277
Location
Essex
Your Mercedes
S500 (W222) 2014. Turbo 4.7 V8 with loads of toys. Superfast luxury.
  • Thread Starter
  • Thread starter
  • #9
I am sending you the test for the rear window


Thanks Malcolm, I've received the test

If it is likely to need a new rear window I hope that it might be covered on the warranty. Otherwise I'll listen to CDs while the window clears
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
Thanks Malcolm, I've received the test

If it is likely to need a new rear window I hope that it might be covered on the warranty. Otherwise I'll listen to CDs while the window clears

If you can fix up that test and it proves it,,then yes a new screen
 

Blobcat

Moderator
Joined
Feb 8, 2006
Messages
38,886
Reaction score
27,587
Location
Grange Moor
Your Mercedes
R171 SLK280, Smart R451, Land Rover 110 County SW, 997 C2S, R1250 GSA TE 40th, CBR600FP
Quite a few 211's had rear windows replaced because of the interference from the screen heater, mine included.
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
Quite a few 211's had rear windows replaced because of the interference from the screen heater, mine included.

This has been ongoing since my very first post,it was all 140's then and the 126 and the antenna was not in the screen on those
 
OP
S500 Pete

S500 Pete

Senior Member
Joined
Mar 9, 2009
Messages
788
Reaction score
277
Location
Essex
Your Mercedes
S500 (W222) 2014. Turbo 4.7 V8 with loads of toys. Superfast luxury.
  • Thread Starter
  • Thread starter
  • #13
Quite a few 211's had rear windows replaced because of the interference from the screen heater, mine included.

Thanks for that, more ammunition if I need a rear screen.
 

Kevin Dawson

New Member
Joined
Nov 13, 2009
Messages
5
Reaction score
0
Hi Malcolm,

Could you please send me the test too, my W204 has just started with the same fault, severe degradiation of signal when the rear heated window is activated.

Kind regards,

Kev Dawson
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
Sorry this test will not do for the 204, all one can do is to replace the rear screen of try a 20,000mfd cap over the screen wires as close as possible to the rear screen connectors
 


Welwyn Merx Limited is a family run business with genuine passion, dedication and 25 years of experience dealing with Mercedes-Benz and AMG passenger cars.
Tel: 01707 395999www.welwynmerx.uk
Top Bottom