coupe (300CD) seat vacuum - PeachParts Mercedes-Benz Forum

#1 05-24-2002, 06:25 PM

I'm trying to figure out the seat-back vacuum on my 85 300CD. The seat-backs are supposed to lock in place, but I can't figure out how they're supposed to work. The manual diagram (80-902) shows a "door contact vacuum swich." I'm wondering if this is the same thing as the interior light switch in the front of the door. It also shows a "vacuum switch" for the backrest and a seat vacuum "element" with an actuating rod.

Does anyone have experience with this system? All I know is that mine is not working (I don't think--very confusing).

Thanks,

#2 05-25-2002, 09:32 AM

There are blue vacuum elements under the fwd end of the seat cushions on both seats. If you get your head down in the floorpan you should be able to see them. Pull the floormat out and un-snap and pull up the carpet at the fwd end of the seat and yu can see the vacuum lines going to them. Not the striped yellow lines they are the locking system, I can't remember the seat back line color (maybe blue??)

If there is no vacuum on the elements you should be able to tilt the seat back fwd without using the latch release button on the side of the seat. With vacuum applied, the elements pull the seat latches closed and you have to use the latch release button to move the seat back.

If you have a hand vac pump you can test / operate the elements. If they are working (will hold vacuum) you should be able to hear them pulling tension on the seat latch springs.

What a useless feature, huh.

#3 05-25-2002, 09:42 AM

I guess I'm wondering how useless the feature is. I suppose it's a safety feature. Do you think disabling the seatback locks would prove dangerous in a crash? I hate to give up the safety built into Mercedes, especially if my children are driving.

#4 05-25-2002, 10:20 AM

There is already a seat back latch release on the seat. If it is already there then why have the safety feature (seat bacs locked in place) plagued with the fact that the safety feature is reliant on vacuum elements for the safety feature to operate????????

Just have the seat back latches engage at all times then you do not have the failure point in the loop.

#5 05-25-2002, 10:33 AM

Quote:

Originally posted by Ron G.
Just have the seat back latches engage at all times then you do not have the failure point in the loop.

I'm not clear on how I can make that happen. Without vacuum, the default is not-engaged (not locked). With vacuum (engine running), they backs are locked.

#6 05-25-2002, 11:11 AM

Exactly what I mean, there is no way to have the seats remain locked in the event of a vacuum pump or vac line, or element failure.

That is why I indicated that it is a useless "safety feature". The latch design should have been such that you always have to push the release button to tilt the seat back and not have to rely on vacuum to activate the seat back locks.

I have had this 85 300CDT for a year and in that time I have realized that these are the most unbelievably poor designed machines I have ever seen.

Holson Adi · #7 05-25-2002, 05:52 PM

speaking of the coupe....

My driver's side quarter window broke yet again........... this thing is pissing me off... I gotta take the car to someone who knows how to fix it properly.

Maybe the dealer...

omegabenz · #8 05-27-2002, 06:41 AM

I got my passenger side one to work by taking the back panel of the seat off and reconnecting the line.

Holson, you need to buy a new window regulator. I tried to fix mine, but for now I just dont roll the windows down, you have to get it lined up so they dont make noise though. I came across this, but I didn't fully investigate it.
http://www.mymercedesparts.com/cranks2.htm

he apparently makes them stronger. Try it out, let me know how it works.

Austin

Holson Adi · #9 05-27-2002, 09:27 PM

Well I checked out why mine doesn't work.
I found out that there are two seat locks. One on each side of the seat.

I learnt that the seat locks work for both sides. As in the passenger's side will also unlock if I release the vacuum for the driver's side seatback.

The problem seems to be that the seatbacks do not lock as they are supposed to. Unless I manually lock the driver's side lock.
The problem is that the left lock on my driver's side seat does not work. It moves freely. It seems like it's disconnected from the vacuum element.
Could that cause my problem?

I hope it's clear enough...

240 Ed · #10 05-28-2002, 04:05 AM

When I had my coupes drivers seat apart to fix the cushion, etc. I applied vaccuum to the pipes and the latch worked, but I can't get it to work with the car on, I guess I am not getting vaccuum to the seats, haven't checked. My locks work only slowly with the engine running, not after. Sometimes the engine won't shut off until I open the drivers door...

I need to fix this because the seat backs are not latched when driving and this is definetely a safety hazard.

Ed