Mercedes-Benz Forum banner

Have some general questions

815 views 11 replies 4 participants last post by  azatrum 
#1 ·
Hi all,
I am still new on this site as I have recently purchased my 95 S420. I am still finding out about all of car's functions and at the same time also finding out what function works and what doesn't. I have done a lot of research on different areas of problems and found out that most of them are all common in these cars. Some of them I have already found answers to and others I have not yet. So I have a few general questions and will appreciate if I could get some answers to those and some corrections to some of my own conclusions.

1: all the power windows work fine but only through the switches in the front. Both window switches on the back doors dont work. I assume its just the switches that need replacement? Is it just the top switch part that normally goes bad or the whole unit including the wires need replacement?

2: Power lock system doesn't work. Light flashes on both doors but do nothing. The manual key insert only works on the passenger door. Locks can be pushed down or pulled up by hand. But during all of this, no sound from the PSE pump at all. On pressing the central locking switch, a noise can be heard from inside the dash on the passenger side. Not sure what that is. But nothing happens.
Have read a lot postings on this topic and my conclusion is the PSE pump motor or the entire pump needs replacement. Please correct if I am wrong.

3: Door soft close only works for both the rear doors. I assume its the vacume motor or assembly inside the front doors is bad.

4: I have a rough idle and hesitation when taking off from a stand still. Once it starts to move than the car all of a sudden gains normal power and hesitation goes away.
My research tells me that I have a bad MAF. Today I disconnected the wire and the idle became normal. I am getting the codes for MAF. The accelerator pedal starts working after being pushed almost half way down. Up till that point it seems as if the pedal is loose or there is a play in it. I thought it was related to the rough idle and the hesitation but I just want to know if this is normal for these cars or no.

Any help is appreciated. Thanks in advance.
 
See less See more
#2 ·
1: all the power windows work fine but only through the switches in the front. Both window switches on the back doors dont work. I assume its just the switches that need replacement? Is it just the top switch part that normally goes bad or the whole unit including the wires need replacement?

No, not necessarily.

The rear child lock maybe the problem.
Try to sync all windows once. i.e draw each one down and then hold the button for 5 seconds. Then draw up and hold button for 5 seconds for each windows 1 by 1.

2 Power lock system doesn't work. Light flashes on both doors but do nothing. The manual key insert only works on the passenger door. Locks can be pushed down or pulled up by hand. But during all of this, no sound from the PSE pump at all. On pressing the central locking switch, a noise can be heard from inside the dash on the passenger side. Not sure what that is. But nothing happens.
Have read a lot postings on this topic and my conclusion is the PSE pump motor or the entire pump needs replacement. Please correct if I am wrong.

You have to do a scan, it will tell you a lot about where the expected leaks are.
It can be as simple as a fuse problem to the PSE pump, or a dead pump.
I suggest to find the fuse ( in the trunk ), pull it out and wait for a minute. Then put it back in and see if things come back to life.

3 Door soft close only works for both the rear doors. I assume its the vacuum motor or assembly inside the front doors is bad.

again, not necessarily. Do the fuse things as listed in 2. and see what happens. If they come alive, even for once or twice. that means you either have a leak or a weak pump in that order of probability.

4: I have a rough idle and hesitation when taking off from a stand still. Once it starts to move than the car all of a sudden gains normal power and hesitation goes away.
My research tells me that I have a bad MAF. Today I disconnected the wire and the idle became normal. I am getting the codes for MAF. The accelerator pedal starts working after being pushed almost half way down. Up till that point it seems as if the pedal is loose or there is a play in it. I thought it was related to the rough idle and the hesitation but I just want to know if this is normal for these cars or no.


Does your car have electronic accelerator or the wire setup ?
I suggest to check for codes in that setup also.
As you said if removing MAF wires fixes it, then it most probably is the MAF.

Another thing to check is the fuel pressure from the distribution rail. A weak pump or a clogged fuel filter can also cause confusion to the computers.
but in your case it seems to be MAF.

regards.
 
#3 ·
Try to sync all windows once. i.e draw each one down and then hold the button for 5 seconds. Then draw up and hold button for 5 seconds for each windows 1 by 1.
Thank you salman108 for all the answers. I will try the window sync thing today and see if it makes any difference.
It can be as simple as a fuse problem to the PSE pump, or a dead pump.
I will definitely check for the fuses. Anyone has any idea if there is any marking or identification on the fuse that controls the pump?
 
#6 ·
Just my 2 cents on the MAF

On my S600 I thought I had a defective MAF. Plugging and unplugging did nothing to change the somewhat rought idle and lack of power. Checked the wires. They were fine. Checked continuity to the LH connector. It was fine.

When I was stateside, I picked a used MAF. Cleaned it with MAF cleaner. Brought it back, plugged it in, and NOTHING!

Took a day or so to calm down. Then took out all the computers under the hood. Do-ox'd both the computer pins and the connector sockets. Found when putting it back together that one of the connectors for the LH computer wasn't seating all the way.

That did it.

Lesson learned: pull and clean all the underhood computers. Then inspect how the connectors set one by one.

Cheers
 
#10 ·
Just my 2 cents on the MAF

On my S600 I thought I had a defective MAF. Plugging and unplugging did nothing to change the somewhat rought idle and lack of power. Checked the wires. They were fine. Checked continuity to the LH connector. It was fine.
When I was stateside, I picked a used MAF. Cleaned it with MAF cleaner. Brought it back, plugged it in, and NOTHING!
Took a day or so to calm down. Then took out all the computers under the hood. Do-ox'd both the computer pins and the connector sockets. Found when putting it back together that one of the connectors for the LH computer wasn't seating all the way.
That did it.
Lesson learned: pull and clean all the underhood computers. Then inspect how the connectors set one by one.

Cheers
Thank you for you input scottpeterd. I am still new to the W140 and am not really sure where those computers are located. I'll appreciate if anyone could provide a little bit help in that area also. I dont want to disconnect something unrelated to this.
 
#7 ·
1: all the power windows work fine but only through the switches in the front. Both window switches on the back doors dont work. I assume its just the switches that need replacement? Is it just the top switch part that normally goes bad or the whole unit including the wires need replacement?
.
Before you change switches etc , check that the rear window lock is not active .
Picture below is the Switch to check .:thumbsup:
 

Attachments

#8 ·
Thank you Merc-S600 for the info. Before your answer came, I had already tried the window syncing thing but no change. anyways it turned out to be the rear window lock. It was on. Turned it off and rear buttons work fine now. I do have another problem now though. The driver side rear window was slow in moving as if the motor was having a hard time moving it, well now it barely moves the glass. It tries though but the glass wont budge. any ideas guys. Bad motor I guess?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top