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  #1  
Old 06-13-2005, 12:45 AM
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Join Date: Sep 2000
Posts: 97
126 Front Seat Electrical Problem (Solved!)

Hello,

I have a 1984 300SD (126 Body Style). The front power seat (drivers) has become inoperable. Absolutely zero movement in any direction

At first I thought it was the seat switch since over the years, they seem to fail often. Having two of the same cars, I swapped it out from the other car but found the switch to be operational.

Fuses looked good, even tried swapping the ice cube relays. No solution

I checked the other (good) car and found that the seat switch normally has +12V coming in to all the controls and a central ground.

The car having the problem has no power (only .13 registering consistently on all terminals) coming into the seat switch control.

Does anyone have a wiring diagram that can tell me how the power is routed? Does it come directly from the fusebox, or is it coming from underneath the seat first?

I remember 14 yrs ago when I purchased the car the previous owner mentioning something about a short in the power seat that required removal of the seat? I am not handy enough (or willing) to take apart the seat these days...the seat worked well until today.

Any idea how much something like this would run at the dealer? Am I overlooking something obvious that could cause this?

By the way the passenger seat works fine...
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1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)

Last edited by 300sd2000; 06-29-2005 at 01:18 AM.
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  #2  
Old 06-27-2005, 11:08 PM
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Join Date: Sep 2000
Posts: 97
well, I'm gonna try taking the seat out completely and swapping the electronics, cabling, to the other car (high mileage one). I might be getting rid of the higher mileage one soon anyway.

I plan to set the seat of the high mileage car to the correct position and then pull both seats out.

I'm hoping it'll be easy to swap out the parts and find the source of the short. Could a loose cable cause this? Any tips on seat removal?
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1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)
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  #3  
Old 06-28-2005, 12:07 AM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
Posts: 1,915
Here it is on a 124

300E Front Seats Removal
Hope this helps
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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html
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  #4  
Old 06-28-2005, 01:36 AM
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Join Date: Sep 2000
Posts: 97
sounds simple enough will give it try here shortly. However, the car with the power seats not working -- I hope its in a position that makes the bolts available to remove?
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1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)
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  #5  
Old 06-28-2005, 01:55 AM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
Posts: 1,915
Had a similar problem... rear of the seat too low.
Had to use small 1/4 " (smaller fit in better) socket with a universal joint removed some of the side trim and went at it from the side of the seat. The bolt by the transmission hump was tougher but I eventualy found a combination that could get at it... patience and a good range of sockets should get you there.
__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html
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  #6  
Old 06-29-2005, 01:21 AM
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Join Date: Sep 2000
Posts: 97
Talking

Undid the bolts and removed the seat slightly, but even before I got it out, noticed a loose 4 or 6 pin connector. Snapped it into place and woila! Seats are working again.

Lucky fix on this one. I was afraid of a short. Glad I tackled this myself. Went thru all the fuses, removal of seat switch, etc.

For future reference the seat switch controls have a large pin and several small pins. The large pin apparently acts as a ground and the small pins have +12 v. Connecting the two with a jumper will move the seat in the various directions.

If no power between the small pin and ground, it aint a seat switch problem, but rather a seat bottom connector/short or fusebox problem it seems.

Hope this helps someone out.

FYI: Seat removal is easiest with a 10 mm socket set. Use a universal jt socket for tight spots and avoid an air socket until loosened first.. I used one and stripped one bolt. Fortunately I found a good replacement bolt of the same thread. You could also use a 10 mm closed end wrench
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1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)
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