Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 08-07-2009, 12:31 PM
Registered User
 
Join Date: Mar 2008
Posts: 98
1987 420SEL power seat doesn't work

None of the adjustments on the front passenger seat of my 420SEL are working except the seat up/down and the headrest. The seat back is stuck in the reclined position.

My car has the memory seats which have adjustment switches on the door panels.

[later edit]: You might want to skip to the last post in this thread.

I've searched for a thread covering this, but didn't find anything. Can anybody refer me to one, maybe?

Or, where can I get the theory of operation and a schematic diagram of the power seat circuit? Would anyone have any troubleshooting and repair tips? Does the power seat relay go bad? How about the door switches? And does the door have to be open in order to adjust the seat?

Any help or suggestions would be appreciated. Thanks.

- retro

Last edited by retroguybilly; 08-18-2009 at 01:16 PM. Reason: later developments
Reply With Quote
  #2  
Old 08-07-2009, 06:53 PM
Registered User
 
Join Date: Mar 2008
Posts: 98
a mistake in my earlier post

It does have memory seats. I didn't realize that when I first posted.
Reply With Quote
  #3  
Old 08-08-2009, 12:13 AM
Hit Man X's Avatar
I LOVE BRUNETTES
 
Join Date: Sep 2004
Location: FUNKYTOWN
Posts: 9,030
Thumbs up

Ever replace the fuses? Old ones hamper the electrical system of this car over time......
__________________
I'm not a doctor, but I'll have a look.

'85 300SD 244k
'87 300SDL 251k
'90 300SEL 325k
'91 560SEL 189k

Eight others from IH, BMW, GM, Ford, and Volvo.

Liberty will not descend to a people; a people must raise themselves to liberty.
[/IMG]
Reply With Quote
  #4  
Old 08-09-2009, 01:46 PM
Registered User
 
Join Date: Mar 2008
Posts: 98
hitmanx, doesn't the fact that it is happening only on one side rule out the fuses, since I think both seat motors get their supply lines from the same fuse?

Please correct me if I am wrong, but I thought that's how I read the schematic.

I removed and inspected the old door panel switch. It looked lousy, so I am going to replace it first.

Let me know if you have any other suggestions.

That seat was out of the car for re-upholstery recently. I wonder if the upholstery shop didn't plug the recline motor back in?
Reply With Quote
  #5  
Old 08-09-2009, 03:37 PM
iwrock's Avatar
roflmonster
 
Join Date: Nov 2003
Location: Hella NorCal
Posts: 3,301
The seat went back, and now it will not go forward?
__________________
-Justin

07 MB ML320 CDI
12 Trek 2.1 Triple
16 Nike Free 4.0

it's automatic.
Reply With Quote
  #6  
Old 08-09-2009, 08:44 PM
Hit Man X's Avatar
I LOVE BRUNETTES
 
Join Date: Sep 2004
Location: FUNKYTOWN
Posts: 9,030
Thumbs up

Lots of things are in an X-circuit, such as RF and LR window on one... and LF and RR on another.

It's worth checking as it's easy and simple.

BTDT
__________________
I'm not a doctor, but I'll have a look.

'85 300SD 244k
'87 300SDL 251k
'90 300SEL 325k
'91 560SEL 189k

Eight others from IH, BMW, GM, Ford, and Volvo.

Liberty will not descend to a people; a people must raise themselves to liberty.
[/IMG]
Reply With Quote
  #7  
Old 08-09-2009, 11:37 PM
Registered User
 
Join Date: Mar 2008
Posts: 98
iwrock wrote: "The seat went back, and now it will not go forward?"

Yes.
Reply With Quote
  #8  
Old 08-10-2009, 12:08 AM
museikm4tt's Avatar
Registered User
 
Join Date: Aug 2009
Posts: 34
probably a bad switch

sounds to me like its a bad switch. same thing happened to my car. the recliner and headrest wouldn't work. i took the panel off and messed with the switch and was able to temporarily move the seats into a comfortable position. but my indie told me its a bad switch. ill get it replaced eventually.


so i would check there
Reply With Quote
  #9  
Old 08-10-2009, 01:01 AM
bsmuwk's Avatar
124.051
 
Join Date: Jan 2009
Location: IL / WI
Posts: 914
Clean out the switch. With age some contacts will corrode and you'll get some gremlins. Follow the below procedure and clean out all the contacts. I've done this once a year to my dad's 300TD and have cleaned out my coupes.

Here's a DIY: http://www.peachparts.com/Wikka/W124SeatSwitch
__________________
-Allen
Artisan Motorenbau
Lakemoor, IL

Chicagoland Mercedes Enthusiast Facebook Group: https://www.facebook.com/groups/mbclubchicago/
Reply With Quote
  #10  
Old 08-18-2009, 01:12 PM
Registered User
 
Join Date: Mar 2008
Posts: 98
My car does have the memory seats. The old switch didn't look good to me, so I replaced it with a new one, but I still have the same problem.

Actually, the seat up/down adjustment does work, and so does the head restraint adjustment, but none of the other adjustments work. I can hear the motor trying to actuate with the other adjustments, but it doesn't move anything. I have the seat removed from the body and would like to put it on the test bench, but I'm having problems figuring out how to disconnect the two wires from the floor harness to the seat adjustment mechanism. It looks like you need to remove a plastic cover before you can unlock the connectors, but how do you remove the cover?

Then I need to figure out how the mechanism and motors is supposed to work. Can anybody give me a crash course on that?

Thanks!
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 12:42 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page