w202 heated rear window

[c13tay]

Still cant get this to work

switch lights up, i can hear relay "click" but no heated rear window.

Tried to look at conections where it joins screen but vert difficult to see - presume contect is being made as the wires arent loose.

All i can think of is that there may be a break in the wire somewhere.

Cos the switch lights up, does that automatically mean that the switch is switching - if you know what i mean ??

No good with electrics so suppose will have to take it to auto electrician

 

[GrahamC230K]

Maybe SAM relay.

 

[c13tay]

Thanks Graham

Presume this is something different to the relay I can hear clicking - tracing it by ear, the one clicking is the really big long one in the relay box behind the fuse box.

Having said that the "click" is a very muted one

Does this control anything else ??? just wondered why it is such a big unit


Chris

 

[pascal]

I presume you checked the HRW fuse first, as its usually on a different circuit to the switch/relay


Pascal

 

[c13tay]

Yes - checked all fuses which in any way mention HRW

Not sure how the switch is wired - the yellow "on" indicator comes on - would that be fed after the relay or before ie does the fact that the indicator illuminates mean the relay is ok ??

 

[pascal]

switch light is usually on switch circuit. HRW itself will usually have a circuit of its own, about 25A fuse. Remember there are 100s of posts here where at first, the fuse was reported okay, only to discover later to be the only problem. It is a longshot, but would alway be my first check.

 

[joe bloggs]

Check the earth point (i forget which end of the window), behind the trim, the screw can be loose, switch the window on and try a test lamp at either end of the window. If it works at both ends of the window then the earth is loose, if it works at one end only the window should work, if not at all then the supply is missing,... the switch lighting and clicking the relay operation is seperate from the main switching supply, i.e the main supply / earth could still be missing even if the switch lights up.

 

[c13tay]

Thanks everyone

As i said not good with car electric but will have a good look at the weekend. So far all the little electrical problems on this car seem to have been caused by the people who fitted the stereo and alrm system for the previous owner. It seems that the connections for the cd changer in boot and alarm wires to back of car run up the pillar, under the headlining, and down the rear pillar. the alarm control unit is behind the stereo/heater controls. Non of the heater bits worked when I got it, multiplug wasnt correctly pushed home !! Will checK plug is on back of HRW swithch correctly. Also they were either lazy or lost a lot of screws - it seems that everything they removed, has been put back with half (or less) the llocated screws.

Hopefully either the switch wont be fully connected or as you say they may have disturbed the earth at the the rear..

 

[GrahamC230K]

Thanks Graham

Presume this is something different to the relay I can hear clicking - tracing it by ear, the one clicking is the really big long one in the relay box behind the fuse box.

Having said that the "click" is a very muted one

Does this control anything else ??? just wondered why it is such a big unit


Chris

Controls all sorts - indicators too.

 

[SWERVE]

202 heated rear window

I had the same problem abt 3 yrs ago on a c250 d the relay is a big one it controls hr window indicators and i think intermittant wipe went to dealers quoted 80 + vat went home took apart relay found a dry joint ran solder iron over it and it fixed it and is still working to this day and car has got abt 250 k on it hope this helps

 

[c13tay]

Thanks for all the replies

tried everything except your suggestion Swerve.

Car is going into local independant for service on Saturday - will ask them to have a quick look

 

[whitegold]

HRW has been Intermittent for ages

and also the wash wipe/indicators have been off a couple of times.
After reading Swerve's post I'm off to investigate the relay, and will post pics /report if that's solved the problem.

 

[pascal]

The multi purpose relay for w202s (wiperwash/flasher/heated r w) is available from Eurocarparts for £47+vat (genuine) and £43+vat (non-genuine), if a disaster occurs:evil:

 

[woodturner-fran]

Would anyone know if it is that same set up with the multipurpose relay on a W210 (see my post back a bit on odd wiper behaviour)


Fran

 

[whitegold]

The offending article!

turned out to be the combined flasher/multifunction Relay.
This is situated UNDER the main fuse board on the driver's side.

Surprisingly, this also controls the HRW, intermittent wipe/wash, as well as the indicators/hazards.

Initially, I suspected the other black box relay, which is held down with an overcentre clamp. However that had no obvious faults.

The combined relay was a very different story, however. It's a swine to prise apart, as my thumb in the picture bears testimony.

I've marked the connections that were cracked on my relay, although I would suggest you resolder all the base to board joints, to be sure.

All functions are now fully restored to normal, including the hit or miss HRW, which was driving me mad by only refusing to work when the car was stone cold.

 

[c13tay]

Sucess at last !!!!

Ended updoing the same as Whitegold

took the relay apart (mine came apart very easily)

only one dodgy joint on mine though - quick re-solder and now all is well.


Thanks all

Chris

 

[tom7035]

Well done guys! Back to old fashioned car REPAIRS - not 'remove and replace' all the time at huge cost!
Wonder how many Dealerships would have even bothered with such a repair (or even have known it was possible in the first place!)

 

[wrichardson1999]

Interesting post, similar symptoms to mine so going to give it a try over the weekend on my W124; replaced my relay a few years ago when the wiper stopped working managed to get one from a mercedes breakers for £20.

Fingers crossed it's as easy as you guys have made out ;-)

Cheers

 

[Billinski]

Heated Rear Window fault also resolved on C200

Further to Whitegold's experience (and thanks for the tip and useful pictures), I also repaired a similar dry/broken pcb contact on the electronic module. i suspect that it was a pretty dry joint at the start and with vibration over the years the contact finally failed.

Important: Disconnect battery -ve terminal before removing any relay module as it can be easily damaged even when you think the power is off.

A touch-up using a soldering iron fixed the problem, and now I can see through the rear window. :-D
Relay module:-
(Gently prise base from cover)

PCB module showing offending dry joint.

(1984 C200 Elegance Auto. Had from new, never let me down)