Rear demister interfering with radio reception

[merc911]

I have noticed that when I use the rear demister that there is some interference in radio reception - most likely due to the aerial being built into the rear window. My car is a 2001 W210 E200. Any comments.

 

[television]

The Rear window noise suppressor( capacitor) is in the rear side panel drivers side.by the side of the glass
Its an electrolytic condenser.they do not have a long life,they can go open circuit or leak

Malcolm

 

[severn]

Most likely its the heated screen itself thats causing the problem. heres how to test.
remove both c pillar trims
disconnect heated rear screen connection at screen leaving suppressor in circuit and get a 55w headlamp bulb and connect it to the removed rear screen connections you will have to temporally extend the leads. The bulb is a resistive load and takes place of the heated rear screen.
turn on the ignition and the rear heated screen. turn on the radio if the interference has gone its the rear screen thats faulty. If not its something else.

Lay money on it being the rear screen

 

[television]

Most likely its the heated screen itself thats causing the problem. heres how to test.
remove both c pillar trims
disconnect heated rear screen connection at screen leaving suppressor in circuit and get a 55w headlamp bulb and connect it to the removed rear screen connections you will have to temporally extend the leads. The bulb is a resistive load and takes place of the heated rear screen.
turn on the ignition and the rear heated screen. turn on the radio if the interference has gone its the rear screen thats faulty. If not its something else.

Lay money on it being the rear screen

If you insert a lamp in place of the window you have then moved the source of interference away from the aerial.the cap is recorded by MB as a source of interference.

Malcolm

 

[merc911]

Thanks for the advice - ill try the supressor, seems a less expensive route

 

[television]

If you unbolt the suppressor you could take it to a local radio shop to be tested. phone the local Television servive guys and ask them if they have an ESR meter as it is the only way they can be tested. a capacitor tester will indicate the value but not the effecientcy.

Malcolm

 

[merc911]

any suggestions as to how toremove the panel that suppressor is behind. Im assuming that when drivers side was mentioned it was a RH drive model.

 

[severn]

If you insert a lamp in place of the window you have then moved the source of interference away from the aerial.the cap is recorded by MB as a source of interference.

Malcolm

The aerial is build into the rear screen? so yes disconnected the heated screen power will stop the interference if faulty. The bulb substitutes the screen and draws a similar power so tests the rest of the system.
Trust me i changed dozens of rear screens for this problem

 

[television]

The aerial is build into the rear screen? so yes disconnected the heated screen power will stop the interference if faulty. The bulb substitutes the screen and draws a similar power so tests the rest of the system.
Trust me i changed dozens of rear screens for this problem

There is no way that the heated screen itself can cause interference. the interference is caused by the spikes and noise (from the engine) on the cables that go to the window, these spikes appear on the rear window element and the antenna shares the same space, so you have a capacitance effect as well as radiated.
The giant electrolytic cap flattens off the spikes and noise and is fitted as close as possible to the window. This is standard practice when it comes to noise etc
There is no way that an element on its own can cause interference, it either works or it does not.
Normal antenna's run from a screened lead and fitted as far away as possible from any radiated noise.

Here we have a separate heated element removable panel, in addition to the window glass its self. Nothing has moved, the element is still intact and working and you say this goes wrong, please tell me how.

Malcolm

 

[severn]

This test is a MB recommended test. Documented on WIS
So tell me why when the heated screen is replaced it cures the fault.
I have replaced many screens and i can say without Any shadow of doubt it cures it.
The unit in the c Pillar is a amplifier for the rear screen antenna.

The interferance will also be present when the heated screen is on and the engine is not running, just with the ignition on so that rules out the engine as a cause of any possible interferance would'nt you agree
Merc911 could confirm this.

 

[television]

I have noticed that when I use the rear demister that there is some interference in radio reception - most likely due to the aerial being built into the rear window. My car is a 2001 W210 E200. Any comments.

The interference that you have, little more info please. Is it on AM or do you only have FM. what kind of interference, crackle,whine etc. Has it always been there, if it is something new and just happened
MB say that if you leave the window turn on for 15 to 20mins at 13.5 volts (engine running) to overcome transistion of the contacts.
They also say that the can bus data cables should be seperated from the antenna lead and moved as far apart as poss.
One more mod was to re route the rear cables going to antenna
Malcolm