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Discussion Starter #1
Hello... I'm kind of new here (been lurking for awhile). Let me tell you the issue I am having.

I have a 2003 E500 with about 70,000 miles on it. I've had the car for about two years and LOVE it. I've always driven Lincolns and this is my first Benz.

I have an issue with the heated seats. I have searched the forums and could not find this issue (although a couple simular).

When I turn on the heated seats, the lights flash for a few seconds then go out, or the lights turn on solid and then go out. Sometimes I get nothing... no flashing lights or solid lights.

I have replaced the primary battery (12/23/2009) and the alternator (03/14/2010). I recently checked the secondary battery and it is running about 12.6 volts. I have also checked ALL the fuses and found nothing blown.

There are no other issues (related to poor voltage) that I have recognized or noticed. Everything else seems to work fine (including all dash systems).

So there you have it. It's only my second post on this sight, and it's a problem. lol. Hope you folks can help.

T
 

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2006 Merc E320 cdi
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981 Posts
Maybe one of the heater pads has a puncture, short or an issue with the wiring.. Either way this might not be an easy fix. I have heard folks that have had issues with the heated seats might have a fuse blown so the button yields no heat.. You're case seems different tho..

I would check all of the electrical connections under the seat to potentially eliminate a loose wire or bad/oxidized connection.. Any water dumped in the car since the seats last worked (sunroof open, spilled water bottle, etc)???

Does the passenger side work ok??

Just thinking out loud..
 

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'07 GL320CDI
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It's the design that the three (or two or one) lights come on when push the button once, twice or three times and that the seats eventually "time out."

Doesn't really sound like what's happening with yours and instead sounds like you have a problem. Yes, the elements can be damaged, and the elements are combined with the upholstery, so both are replaced. Some have added alternate heat elements, i.e. keeping original upholstery, and some rewiring instead.
 

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Discussion Starter #4
Maybe one of the heater pads has a puncture, short or an issue with the wiring.. Either way this might not be an easy fix. I have heard folks that have had issues with the heated seats might have a fuse blown so the button yields no heat.. You're case seems different tho..

I would check all of the electrical connections under the seat to potentially eliminate a loose wire or bad/oxidized connection.. Any water dumped in the car since the seats last worked (sunroof open, spilled water bottle, etc)???

Does the passenger side work ok??

Just thinking out loud..
I was leaning towards a bad/oxidized connection. I do not know of any moister in the car of any kind, but I'm not sure.

I should have mentioned, that the issue is related to both seats. Also, if one seat would happen to work and I try to turn on the other seat, it usually kills both seats. I will check the plugs under the seats today and see what I find. I have glanced at them, but never actually unplugged them to examine them.

I might also add this: once the seats flash out or turn off, they will not turn back on for several hours. That's the part that confuses me. They act like the battery is too low to operate the seats (or the system is not charging... it is), but it also seems like a connections problem. Seems to me that they are struggling to get enough voltage to run so they shut down.?.?.?
 

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Discussion Starter #5
Check all the plugs in the main power strip on the bottom of the seats. They all appear to be in very good shape, still having the dielectric grease in them. I am baffled?!?!?!?!
 

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'71 Pinto
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Long shot but pull f40 @ interior fuse panel (driver side) wait a minute or two and reinstall to attempt upper control panel (UCP) reset. If this does not work check CAN B connector wiring located @ right side passenger footwell. If you need instructions to remove panel PM email address include VIN and I will supply part # for worst case scenario whereas UCP “may” need replacement (for comparison shopping, OEM new - parts.com about $163).
 

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Discussion Starter #7
Long shot but pull f40 @ interior fuse panel (driver side) wait a minute or two and reinstall to attempt upper control panel (UCP) reset. If this does not work check CAN B connector wiring located @ right side passenger footwell. If you need instructions to remove panel PM email address include VIN and I will supply part # for worst case scenario whereas UCP “may” need replacement (for comparison shopping, OEM new - parts.com about $163).
Pulled the fuse today... No go. I will look at the kick panel tomorrow morning. Thanks for the help.
 

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Discussion Starter #8
Long shot but pull f40 @ interior fuse panel (driver side) wait a minute or two and reinstall to attempt upper control panel (UCP) reset. If this does not work check CAN B connector wiring located @ right side passenger footwell. If you need instructions to remove panel PM email address include VIN and I will supply part # for worst case scenario whereas UCP “may” need replacement (for comparison shopping, OEM new - parts.com about $163).
I'm looking at the attachment you sent. Is that pannel the kick panel our actually the front part of the floor? Thanks.
 

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Discussion Starter #10
Long shot but pull f40 @ interior fuse panel (driver side) wait a minute or two and reinstall to attempt upper control panel (UCP) reset. If this does not work check CAN B connector wiring located @ right side passenger footwell. If you need instructions to remove panel PM email address include VIN and I will supply part # for worst case scenario whereas UCP “may” need replacement (for comparison shopping, OEM new - parts.com about $163).
PM Sent.
 

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Sorry to revive a really old thread here...
I have a similar issue to tda13's issue with his e500, and was thinking this would be the best place to start...
The issue with my 4Matic 2004 E320 wagon heated front seats is almost exactly the same as described above, except the driver seat heated seat will not turn on full heat unless the passenger side is on full heat. If I try to adjust the level by pressing the heated seat button for either seat, both heated seats will turn off. The behavior is always the same no matter how many times I try this, or at what temperature the car is at. All the plugs under the seats are completely clean and shiny, and the CANBUS connector in the footwell is totally clean as well. Should I start looking for an upper control panel replacement too, or is there some other direction I should go here?

Thanks for considering my request for help :)

Peace!
 

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'71 Pinto
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4,512 Posts
“May” be control unit, definitive diagnose have someone pull fault codes. Steadfast on replacing parts rather than pulling code(s) here are compatible part #s to shop used: 2118202685, 2118203626, and current 2118702026. See attachment for a better understanding of system.
 

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Konigstiger,
I was not sure if you'd even reply, but I sure am glad that you did.
First, I want to say thanks for helping fellow benz owners all of these years. -Not sure if you get thanked for all the timely, accurate and useful info that you provide, but I VERY much appreciate it. I have utilized your data on many posts that you've made over the years to repair my vehicles, and am amazed at the time and attention you spend to help others!

All those PDF's were super useful in understanding the heated seat system in my wagon. I will check codes first with my iCarsoft unit, but have a suspicion that the issue is the HS control unit under the front driver's seat. More to come....
 

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Well, after diagnosing the heated seats system in my E320 with my iCarsoft MBII, it appears that the N25/7 HS control module is faulty. OK... that's pretty cheap used on Fleebay.

2603370
 

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Ok, so replacing the HS control unit did the trick! Two of the leads on the control unit were corroded. Figures!
 
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