Electric seat troubleshooting 87 SDL - PeachParts Mercedes-Benz Forum

macthomas · #1 10-23-2005, 11:43 PM

I need some help. I have an 87 300SDL. The driver seat electrics work but the passenger seat does not. Not even a click.
What I have done/looked at:
Replaced the fuses (#2, 15, 17, A, B)
Verified that the seats plugs are all plugged in.

What else can I do or check?
Thanks

sixto · #2 10-24-2005, 12:04 AM

Does it work with the door open but not with the door closed?

Get some Caig Deoxit and spray liberally into the switches. This is worth doing in all the seat and window switches.

Sixto
87 300SDL

macthomas · #3 10-24-2005, 12:13 AM

Quote:

Originally Posted by sixto

Does it work with the door open but not with the door closed?

Get some Caig Deoxit and spray liberally into the switches. This is worth doing in all the seat and window switches.

No, doesn't work at all no open not closed.

Where do you get the Caig Deoxit and where in the switches do you spray it?
Thanks for the help.

sixto · #4 10-24-2005, 01:01 AM

I've seen it at electronics supply shops. Not Radio Shack but the really nerdy stores

Spray it liberally into the slots that the switch posts or rockers go through while working the switches. It'll find its way to the contacts.

Sixto
87 300SDL

BrierS · #5 10-24-2005, 05:28 AM

Sixto certainly should have you in the correct direction. You should find two 12 gauge wires serving the right side switch assembly from the auxillary fuse holder. Both should be red. One should have a white stripe and the other a yellow stripe. Ground wires serving this portion of the circuit are 18 gauge, brown and should be found to the left of the instrument cluster.
Steve

donbryce · #6 10-24-2005, 11:46 AM

If your switch contacts are corroded, one or more of the functions may not work. If nothing works, I'd suspect something else, but it is possible that all the point are corroded. I just finished reposting a procedure on switch cleaning that you might try.

macthomas · #7 10-24-2005, 11:11 PM

The switch is new, the connections under the seat look clean. Any chance it could be the diode or seat relay that would effect only one seat.

BrierS · #8 10-25-2005, 06:48 AM

Quote:

Originally Posted by macthomas

The switch is new, the connections under the seat look clean. Any chance it could be the diode or seat relay that would effect only one seat.

The K5 Power Seat Relay (an ice-cube relay) feeds fuses E and F, which as you know, are 25 amp fuses. Output from those fuses is via four wires, two each left and right seats. In viewing the schematic, it does not seem possible for the relay to work for one side and not the other. If you have a spare relay or want to borrow one from any of the other locations to try, you could certainly eliminate that possibility. The relay is at the depth (rear) of the fuse/relay box centered between relay "A" (another ice-cube) and "I" (the diode you were asking about). Good dexterity and/or small hands will help with R&R of that relay and/or the diode.

You may already know you can remove the power seat switch from the door without removing the panel. In my troubleshooting manual it states, "If you power seat is not moving 80% of the time a new switch will solve the problem. Be sure and check the fuse box first!" Before jumping to replacement I would check for voltage and ground. You can supply either/both with test leads to confirm the state of the switch. At the same time, you will be able to make certain the power feed connections are proper.

macthomas · #9 11-01-2005, 12:32 PM

Still no luck... Thanks all for the advice.

I have power leaving the fuse box and power to the seat. I am wondering if between the switch and the seat there is a problem.

I think the passenger side window was broken out at one time and I am wondering if when the previous owner replaced it some wires got cut or not reconnected.

Next stop is door panel off.... I heard this was a pain in the butt... true??

Thanks again for all the help.

brandlj · #10 11-01-2005, 06:36 PM

Door panels are not that hard to remove. You just have to remember that after you remove the screws to the armrest, the screw behind the inner door handle, the two screws on the chrome piece at the door striker, that the panel is HUNG onto the door by these very brittle pieces of plastic that fit into holes in the steel panel of the door. DO NOT YANK IT OUT!! Gently push the panel UP from the bottom and they will unhook from the door.
If you yank it out you will snap the plastic hooks and then it will be very difficult for the panel to attach to the door.

Take your time. The plastic pieces get brittle with age.

John

P.S. I believe that are two more tiny screws that hold the plastic piece on the back edge of the door by the window. You can see them when you open the door.

donbryce · #11 11-02-2005, 09:44 AM

Quote:

Originally Posted by macthomas

The switch is new, the connections under the seat look clean. Any chance it could be the diode or seat relay that would effect only one seat.

If the switch is "new", I assume you didn't install it yourself or you wouldn't be posting this query, so either the switch is a replacement/used "new", which could be corroded inside and/or improperly connected, or it is off the shelf "new", but possibly not connected (perhaps the previous owner had regulator or motor problems and decided to leave it unplugged).
Older switches were hard-soldered to the wiring harness. However, I think a 1987 would be the newer style switch and harness, but its still possible the replacement (if used "new") is from an older donor. There's a thread on here someplace (a search would find it) with the connections and how-to on connecting a newer style plug-in switch to the older wiring, I think, which may be useful if its an older style switch. You might be better off to get a newer style one though if that is the problem.
BTW, it's not necessary to remove the door panel to check the switch either. Just pry off the trim plate and undo the 2 screws on its left and right side, then manouvre it out (or, at least that's how the 380SE W126 is constructed. Yours may be different).

BrierS · #12 11-02-2005, 08:56 PM

If you have to remove the door panel, you have already been correctly told it is not a difficult job. In fact, after doing it once you will never hesitate doing it again.

I'll add a couple of steps. Unthread the lock button/knob. Remove the door latch black plastic trim cover back of door hidden when the door is closed(single screw) pull out and down on the bottom to release the hook at the top. Pull the power seat switch knobs. They are snapped on so pull straight out with a good snap. These can be hard to grip so be careful not to put pressure side ways. I have used needle nose pliers in conjunction with my thumb and finger. The manual says not to use a tool since you risk breaking off the control pins. After those are off, look at the largest pin (center) and remove the small black plastic C clip. One of mine was missing and I have left it that way for two or three removals. A small bladed screw driver works good for this but still be careful not to break the surrounding pins. Next is the power seat switch cover. Remove the black cover surrounding the inside chrome door pull. To do this, insert a small, flat blade screwdriver from the top rear corner and pry gently outward on the top edge of the cover. Once the top edge is loose, you can pull the cover straight off from the door. Notice the four clips that hold this cover in place. As the book says, "cautious finesse seems to work best here." Next a 10mm socket with extension to remove the bolt securing the top of the armrest to the steel door panel. Once the bolt is removed, pull out slightly on the top of the armrest you just unbolted enough to clear the door panel. While holding the armrest in that position, push forward (toward front of the car) on the black plastic door pull frame. This will release the frame somewhat but you'll still have one more step to complete its removal. On the backside of the frame you should see a rod attached to the back of the chrome door opening handle. With the chrome handle in the closed position, use a flat screwdriver to remove the end of the rod. It is in a plastic clip and you will need to pop it upwards. Now you can remove the black frame which has plastic hooks on its backside. These hold onto the steel portion of the door so don't get rough with them. The piece slides forward and backward not in and out. If you have to remove the driver's door panel, you will need to remove the interior portion of trim controling the remote mirror. A small flat screwdriver will pry the nearly hidden piece at the forward portion of the mirror control lever. Once it is popped, the remainder will pull straight backward. Now it is time to see if the top clip of the triangular piece of trim beyond the mirror control is broken or if you will be the lucky one. Toward the top of the trim piece there is a plastic, pressed clip that has been pushed straight in and need to come straight out. A long, wide blade screwdriver will either be your friend or your temporary foe. Don't get discouraged if it breaks. Once it is popped out or broken off, there is a hook at the bottom that will release. The triangular trim piece will pull off around the remote mirror's naked mechanisim. There are NO screws holding the door panel. If you can, put the window down so as to get a better angle on pulling/pushing the panel upwards. It lifts straight up. NOT outward. There are a series of plastic hooks fastened to the backside of the molded board panel that you don't want to break. Once it lifts free of its spring steel clips at the top near where the window dissappears, you still need to unplug the light at the bottom of the door panel. There should be enough wire length to accomplish this easily. I made new plastic for mine and used 3M trim adhesive to put it on before re-installation of the panel. The panel will require either two people pushing in so as to get all of the hooks into their respective slots or as I have always done it solo, use your knee, thigh and both hands. You will be able to feel when they are all in place before pushing down because there will be no gaps. Reverse everything else.

If you want some great back up, contact **************.com and buy their W124 Door Maintenance and Repair book. The illustrations alone are worth the meager price. Most everything I typed is from their book with a few things from my own experiences. If you break the top clip of the triangular trim piece, PM me and I'll explain a neat fix w/o having to buy a new piece.
Steve

macthomas · #13 11-04-2005, 09:33 PM

WOW thanks for the help. I have some time tomorrow so I will give it a try and let you know how it turns out.
Thanks

macthomas · #14 11-05-2005, 07:08 PM

Ok... I have power to the seat (under the seat) no power to the switches.
Under the seat, none of the posts that connect to the wirest that run to the switch have power.
Ideas?
Rick