SL/R230: Heated rear window not working
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Joined: Jan 2021
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SL400 Edition 2016
Heated rear window not working
Hi everyone,
I have a 2012 R230 SL350, UK model and the heated rear windscreen is not working.
I put a multimeter to it by connecting the black wire to the door latch bolt for the earth and touched the positive on the heated window lines and got 0V.
The key was in running position and the heated screen button light was on. Also checked the 30amp fuse an is ok.
Any ideas what it could be please?
I have a 2012 R230 SL350, UK model and the heated rear windscreen is not working.
I put a multimeter to it by connecting the black wire to the door latch bolt for the earth and touched the positive on the heated window lines and got 0V.
The key was in running position and the heated screen button light was on. Also checked the 30amp fuse an is ok.
Any ideas what it could be please?
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Joined: Aug 2020
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From: Gretna, NE
'03 SL55 Black, '03 SL500's Aegean, Mars Red, Tazanite, Alabaster, '11 S550 Flint Gray
The power for rear window heat is provided by K40/5kU (relay U in the rear fuse/relay module). It is fused by F53. With the control activated, check for voltage at connector I3 on K40/5. If you have voltage there (12-13V) check the wire, connectors, and suppression capacitor to find out why you aren't getting power back to the window. If you don't have voltage, try swapping out the relay.
Thread Starter
Newbie
Joined: Jan 2021
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SL400 Edition 2016
The power for rear window heat is provided by K40/5kU (relay U in the rear fuse/relay module). It is fused by F53. With the control activated, check for voltage at connector I3 on K40/5. If you have voltage there (12-13V) check the wire, connectors, and suppression capacitor to find out why you aren't getting power back to the window. If you don't have voltage, try swapping out the relay.
Relay is good, is there a connection of some kind that comes loose from the operation of the roof that I could check as well, I don't know where to look or if the roof has to be part open to see. Not sure where or what the suppression capacitor is.
Thank you again.
MBWorld Fanatic!
Joined: Aug 2020
Posts: 1,326
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From: Gretna, NE
'03 SL55 Black, '03 SL500's Aegean, Mars Red, Tazanite, Alabaster, '11 S550 Flint Gray
I has a connector (X19) that is right side just above the roll bar cylinder. The capacitor is C3, left side under the C-pillar trim, it looks like a wiring pigtail. The capacitor is in parallel, but there is probably a crimp connection that could cause problems. Has to be one of those spots or the wire itself.
Thread Starter
Newbie
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SL400 Edition 2016
I has a connector (X19) that is right side just above the roll bar cylinder. The capacitor is C3, left side under the C-pillar trim, it looks like a wiring pigtail. The capacitor is in parallel, but there is probably a crimp connection that could cause problems. Has to be one of those spots or the wire itself.
I’ve been trying to see a connector but I’m not sure where or what the X19 looks like. A photo would be great if available? Do I need to remove any panels to access it or is it straight forward to see it?
Many thanks.
MBWorld Fanatic!
Joined: Aug 2020
Posts: 1,326
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From: Gretna, NE
'03 SL55 Black, '03 SL500's Aegean, Mars Red, Tazanite, Alabaster, '11 S550 Flint Gray
Your have to take off the right rear panel that covers the hydraulic cylinder for the roll bar. The X19 connector should be just above the pawl mechanism. Do what Bob suggested first, if you have continuity to ground (with some resistance from the heater), then the wire and connector should be good and you can look elsewhere. If not, check X19, the suppressor, and the ground point (W6 if I remember correctly), it is on the back of the left rear strut tower and you need to remove trunk trim to get to it.
When you say the K40/5kU relay is good, do you mean that you have voltage at socket I3 on the roof module when the defroster is on? That is still test #1 if you haven't done it. I would leave it connected and back probe it if you can. Sometimes you can have voltage under no load, but it will arc out under load.
When you say the K40/5kU relay is good, do you mean that you have voltage at socket I3 on the roof module when the defroster is on? That is still test #1 if you haven't done it. I would leave it connected and back probe it if you can. Sometimes you can have voltage under no load, but it will arc out under load.
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SL400 Edition 2016
Your have to take off the right rear panel that covers the hydraulic cylinder for the roll bar. The X19 connector should be just above the pawl mechanism. Do what Bob suggested first, if you have continuity to ground (with some resistance from the heater), then the wire and connector should be good and you can look elsewhere. If not, check X19, the suppressor, and the ground point (W6 if I remember correctly), it is on the back of the left rear strut tower and you need to remove trunk trim to get to it.
When you say the K40/5kU relay is good, do you mean that you have voltage at socket I3 on the roof module when the defroster is on? That is still test #1 if you haven't done it. I would leave it connected and back probe it if you can. Sometimes you can have voltage under no load, but it will arc out under load.
When you say the K40/5kU relay is good, do you mean that you have voltage at socket I3 on the roof module when the defroster is on? That is still test #1 if you haven't done it. I would leave it connected and back probe it if you can. Sometimes you can have voltage under no load, but it will arc out under load.
So to access the X19 and suppressor is it the inside C pillar trims that need to be removed? Not sure how to do that? Or is it from inside the trunk? Does the top need to be part open or can it be closed while doing it?
I have another issue now where the illumination on the white surrounds on the rev counter and Speedo keeping going off and sometimes come back on but I suppose I need to start another thread for that.
Thanks again for your support.
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MBWorld Fanatic!
Joined: Aug 2020
Posts: 1,326
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From: Gretna, NE
'03 SL55 Black, '03 SL500's Aegean, Mars Red, Tazanite, Alabaster, '11 S550 Flint Gray
Just to back up a bit: 1) Have you tested voltage at connector I3? 2) Have you checked for continuity as Bob described above? 3) In your original post, you said that you don't have voltage on the wire to the window. Where did you check this?
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Thread Starter
Newbie
Joined: Jan 2021
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SL400 Edition 2016
Not sure what I did but it was a cold evening last night and got in the car and tried the rear demist and it worked. When I changed the relay the other day I didn't have a chance to ‘field’ test it with a misted up window and may not have followed the instructions properly after I installed it.
All good now. I just need to try and sort out my dashboard instrument lights on the rev counter and speedo that have a mind of their own.
Thanks again for all your valued input!
