1986 300E power seat won't move forward and tilt up & forward - PeachParts Mercedes-Benz Forum

jrmd01 · #1 11-17-2003, 10:07 PM

I own a 1986 300E and the power seats are not functioning correctly. I did a search on power seats and some people on this forum were able to fix their problem by changing or cleaning the switch.

My driver's seat will not move forward, nor will it tilt up & forward. All other functions work including the head rest. When I press the switch forward, I can hear a single click under the seat, but nothing happens. I don't think the motor is bad because the seat will adjust in all other directions fine.

I am confused and don't know where to begin trouble-shooting this problem
1. Does the "click" mean that the switch is engaging the motor?
2. Does the motor moving the seat backward also power the seat forward? I hoping it's just a cable or something.
3. Does anyone know how many motors are on these power seats?

I'ver tried cleaning out the switch w/contact cleaning solution from radio shack but it has not helped.

Is there a way I can manually move the seat forward?

Please advise...

Thank you,

jrmd01@yahoo.com

dakota · #2 11-17-2003, 11:57 PM

I'd still suspect the switch as the culprit. I would take the switch out, and then, on a bench or table, over a large cloth, take it apart and clean it thoroughly. It's full of little springs and BBs, but just be careful and you should be fine. Clean all contacts and see if that doesn't do the job.

sbourg · #3 11-18-2003, 10:07 AM

Your post implies you think there is one motor. There are separate motors for each function. One could be bad and the rest fine. However, if the seat moves back - for instance - but not forward, the motor is likely fine.

On our 102, the right/left switches could be swapped (though the switches now controlled different things). This allowed verifying that the switch was the culprit in our case.

Steve

donbryce · #4 11-18-2003, 03:31 PM

...The Range Rover guys buy MB seat switches because they are cheaper than their OEM, apparantly. Here's a link to an article on cleaning one: http://www.disco2.com/howto/homemechanic/seatswitchclean/

I know I found a better article somewhere, but this is close. And, there are posts on cleaning MB switches here too. Good luck!

jrmd01 · #5 11-18-2003, 06:15 PM

I own a 1986 300E. The driver's seat will not move forward, nor will tilt up and foward. All other functions work fine, even the headrest.

I did a search and many have solved their power seat problems by cleaning the switch. I have also been advised by Forum members Dakota, Sbourg, and Donbryce to check, clean, and replace the switch.

I took out the switch (I didn't disassemble it) and sprayed it with contact solution from radio shack. Problem still existed.

To double check if the switch was the culprit, I put the suspected faulty driver side switch on the passenger door and it worked fine. That means the switch is good.

I put the good switch from the passenger door on the driver side and get the same sypmtoms...I hear a single click under the driver seat, but nothing happpens.

Since the switch proved to be good, it must be something involving the motor or the cable.

Sbourg, you mentioned that if the reverse works, then it probably isn't the motor. Do you know if the motor moving the seat back also moves the seat forward? If so, then I suspect it's the cable (I don't know if that's good news or bad news).

Do I now remove the driver's seat to find out what's wrong or can I still trouble shoot this problem without removing the seat? If I have to remove the seat, which (and how many) bolts will I have to remove?

...can anyone advise me on my next steps?

Thanks in advance for any help/opinions.

jrmd01@yahoo.com

vnoronha · #6 11-18-2003, 06:33 PM

There are three motors and three cables for these seats. If necessary, removing the seat is not difficult (four 10mm nuts and a cable harness) but you might need a helper to help lift it out of the car. Once on a bench, you can easily access the motors and cables. But if the seat does not go forward/reverse, getting to the mounting nuts is a b**ch

However, it is easier to check the switches first, if the front of the seat goes up, the front up and down motor is fine, if it goes back, the forward and back motor is good, etc. and you just need to clean the switch contacts.

Good luck

dakota · #7 11-18-2003, 07:05 PM

jrmd, it sounds to me like you have thoroughly eliminated the switch. So now maybe it's time to take the seat out, but as vnoronha said, it may be tough. There is a bolt thru the seat track at each end. I don't know how you can get to the aft ones. Are they visible or have you moved the seat all the way back? I'm thinking that I would try to see if the motor is getting power in all modes...you may have to trace the harness to get at it upstream, but that may not reveal the problem if it's downstream of where you test. How about in the door area? Any breaks in the wiring from the switch to where it jumps between the door and the jamb? You may need a schematic. Let me know and I'll try to dig one up if you need it.

Freestyler · #8 11-19-2003, 01:30 AM

My '86 300E has a tendency to get the drivers seat back stuck if i recline the seat. -Only response is a click from under the seat!

First time it happened i had the seat FULLY reclined and did not want to drive around like that. So i pulled and yanked the seat while activating the switch and all of a sudden it worked.
I have since found out that if i lean a little bit forward while activating the switch, it works fine.

Maybe you could try to push/pull the seat before taking it all apart?

Freestyler

donbryce · #9 11-19-2003, 10:52 AM

I recall that the seat back in my 380SE was reclined way back when I first looked at the car, and it was upright when I purchased it from the second owner, but the switch never worked right. The guy I bought it from told me that he unplugged the connector and somehow polked around the female plug with a length of wire until he made the connection that turned on the motor to bring it back up. When I eventually got around to checking out the problem, there were 2 breaks in the seat springs that had chaffed the wires, causing a short and an actual break. Everything worked fine after I fixed the wiring. Perhaps a broken wire or short is causing your problem too. I'd try using a jumper wire to move it forward/backward to get at the bolts, remove it, and do a thorough examination on the bench. Worse that could happen would be a blown fuse, which mine did every time I tried using the switch.

jrmd01 · #10 11-19-2003, 11:48 AM

Thanks to everyone who responded.

From everyone's suggestions/experience, it's seems more likely that something is wrong with the wires. I'll try to probe around the wiring harness to see if I can get the motor some "juice".

If that fails, then I'll remove the whole seat and inspect it. Hopefully I can still get to the rear bolts.

By the way, I was just wondering...since I can hear a click, is it possible that a gear or cable is stuck? I'm hoping the motor is good and not stuck, since the seat will move backward. (Assuming the motor that moves the seat forward, also moves it backward).

I'll post an update on Monday, but I'll still check this website for anymore advice / experience anyone had with this particular problem.

Sincerely,

jrmd01@yahoo.com

donbryce · #11 11-19-2003, 12:18 PM

I think the click you are hearing is a relay. The switch connects/disconnects a low amperage wire that powers a relay coil, in turn making/breaking a higher amperage connection to the motor. Like a power window motor, the switch and relay swap the motor + and - terminals to make it run forward or reverse. I'd be looking at the wiring to the motor from the relay.

jrmd01 · #12 11-23-2003, 08:19 PM

I tried to remove the seat today (Sun 11/23/03) and I can't get to the rear bolts, it's nearly impossible...I give up.

I know it's not the switch (see my previous post). I have no choice but to take this to a mechanic. Hopefully it won't cost too much to fix. If I couldn't get to the rear bolts, I have NO IDEA how the mechanic will be able to get to those bolts. It's so frustrating...I guess I'll have to bite the bullet.

Thanks everyone for your input.

jrmd01@yahoo.com

DavidWeis · #13 01-05-2004, 06:33 PM

What did it turn out to be?

Dave

jrmd01 · #14 01-06-2004, 08:51 PM

UPDATE: I tried to take the seat out to look underneath, but it's impossible to get to the rear bolts.

I have access to the wires infront of the seat, but I am clueless to which wires control the motor to move the seat forward.

I don't have enough money to take it to a mechanic, so I'm just using some cushions for now. Anyone have a ballpark figure on what this might cost me?

jrmd01@yahoo.com

jrmd01 · #15 01-18-2004, 11:25 AM

Well I took my car in to a mechanic. He said that he thought it was the relay because he can still hear a click when he presses the button. He will replace the relay and I have my fingers crossed that it'll work. A new relay is around $600, I opted for a used one at $100.

I trust this mechanic because he only works on mercedes. He's a german guy who's worked on mercedes for MANY years.

He told me that he first suspected the switch because that is usually the part that goes bad. I told him I eliminated that possibilty by testing the switch on the passenger side.

I'm having other minor work done on the car. When I get it back I'll keep everyone posted on how it went.

jrmd01@yahoo.com