CLS Heated Rear Window

[Eggsy01]

Hello, my first post!
New Forum member with his first Mercedes, who's been looking through various threads from way back on various subjects, the people here seem to know a thing or two. Most refreshing!
My heated rear window doesn't appear to work, the button indicator comes on for about 10 mins. I have searched threads, checked and swapped relays, checked fuses etc. I've checked its actually connected, checked for voltage at connector and found a slow rise to 12 ish volts at plug until connector plugged in then it drops to zero. The slow rise leads me to believe its not the window, but I don't know. What and where is this heated rear window control unit I keep reading about?
Any help would be appreciated.
Thanks for taking the time to read this.
Eggsy.

 

[Cole@MBS]

The rear sam controls the heated rear window, thats the relay box in the boot, thats the most common fault for screen faults, dont show fault codes as a rule so simple muti meter skills needed to test which it sounds like you have done..................my next move would be another sam......

 

[Eggsy01]

Thanks for that swift reply.
I had a good look around that unit, I take it the SAM is the fuse/relay box?
I found the relay above the one that should power the rear screen would click with the HRW button, I did wonder if both should click? Swapped them over as they're identical to no avail. Perhaps I've got a dry joint in there being a high load consumer, a common source of problems you say?
Gotta be worth seeing if it'll come apart.

 

[EmilysDad]

..... Perhaps I've got a dry joint in there being a high load consumer, a common source of problems you say?
Gotta be worth seeing if it'll come apart.

Not uncommon in a Smarts SAM http://www.evilution.co.uk/index.php?menu=info&mod=952 The worst that can happen is that you find & fix the fault.

 

[Eggsy01]

Again thanks.
I've been out in the cold having a look, and whilst there cleaning & remaking all the earth points down there, JUST in case!
Anything I should be aware of before removing SAM unit?
I imagine disconnecting the main battery is a good start, but otherwise just a simple removal?
Thanks.

 

[Eggsy01]

It would appear I've solved my rear window problem.
Whilst looking into what was involved in removing the SAM unit late the other night, I decided to remake the 3 earth points I could see, one has 5 or 6 earth wires on it. Loosening the nut and giving the terminals a spin and a little contact cleaner to aid cleaning. On trying the window the following day, I was surprised and relieved to see it working! A nice simple fix for a change.
I've done the same with any body earth connection I've seen now, can only be a good thing.
Hopefully this will be of some use to anyone with a similar problem.
Eggsy.

 

[Eggsy01]

I got ahead of myself!
Window worked, but intermittent. Replacing the fuse box cover caused it to work, close the boot, and nothing!
Removing Sam unit revealed a loose, burning out connection at plug 20, single red cable. Continuity between pin and fuse 10 confirms it, now to try and remake it good.
Fingers crossed please.

 

[television]

Good luck in trying to fix that, these things are possible even if it means bringing a new wire out from the SAM and doing another join.

 

[Eggsy01]

So far so good.
Tested window yesterday and used today a few times, all good.
I'd like to solder a new wire to pin then join to that, but access to pin isn't that great so we'll see.
Cheers.