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S420 Problem...No Problems!

19K views 27 replies 16 participants last post by  MAVA 
#1 ·
Hi Guys,

I think I have a serious problem with my S420 for the first time in a year of ownership;

- She runs smooth
- No codes
- Gear change perfect
- 23.9mpg on a highway run
- No malfunction lights
- Everything works

It seems like there is nothing wrong with the car...am I missing something?

Now there is nothing to fix/tinker....I don't know what to do!

:D
 
#3 ·
Hey, you can come over and help me work on mine! :)
 
#4 ·
and very brave -- the Mercedes gods have got your number now! If you're looking for something to fix, then check out your blower motor regulator,. I have an S420 too, which is the best car I have ever owned.
I was quite content to live with the output of my blower, I thought was working well until we got a couple of really hot days and the significant other complained about the lack of cooling air flow. I took off the plenum chamber, removed the cabin air filter (which will be replaced), and checked out the blower motor. I had heard the regulators regularly fail, so was interested to see how much oomph the motor would have with full voltage (the regulator adjusts the grounding voltage of the motor -- should make a fully open circuit at battery voltage when the maximum fan speed is required) so I grounded the negative pole (blue wire) to the metal housing. Take note -- the motor is wired to be live when the battery is connected, regardless of whether the ignition is on or what air conditioning controls are set at, so use some caution or a big spark and burns are possible. In fact I think that the blower motor runs all the time the ignition is on, regardless of the air-conditioning controls -- they just govern its speed. I suggest using 10 amp wire to ground the pole -- the circuit is fused at 15 amps, so you shouldn't do the motor any damage. So here's the procedure --

Fully open the bonnet( vertical)
remove screws holding air plenum
disconnect vacuum lines (red and green -- four of)
disconnect air temperature sensor and if fitted coolant temperature sensor (these just twist/pull out) some cars will also have a wiring harness connector to disconnect
jiggle and lift up the plenum -- don't drop the screws anywhere you can't get them back from
remove cabin filter to reveal blower motor and fan.
Start engine and set interior fan control to maximum speed without cooling (press EC button) -- note speed and sound of blower motor and fan. Close off rear compartment and side window vents (this will let you judge airflow through the centre dash vents).
now step outside the car and connect a little piece of 10 amp wire between the negative pole/brush holder (the blue wire leads to it -- it projects from the upper part of the motor body -- you should see a small copper end piece with a hole in it -- push these stripped end of the wire into the hole and firmly put the other end to ground -- you can use the cast blower casing)
it's likely the fan speed will increase because you now have an open circuit with very little resistance
if the speed increases a little, then your regulator is probably okay - it will always add some resistance to the circuit
if it increases a lot (mine put out at least twice as much air as before) then the chances are your regulator has given up (or there is a fault in the switches or connectors). I know that the ventilation systems in these cars are very complicated -- if someone knows of a better way to set the interior controls for the fan speed at a maximum please let me know. you can also use a multimeter to measure voltage across the polls when the motor is running.
That's where I'm up to -- a new regulator arrives from the USA next week, as well as a new filter. I will do a quick update after fitting them.
Meanwhile -- enjoy a trouble-free run you lucky %$##!!
 
#5 · (Edited)
Congrats , Thats makes 2 of us running Troublefree just that i'm on my little over 3rd Year now without any Problems ( Exept 1 Bad Petrol Fill ) .
Keep up the Maintenance like i do ( Oil,all Filters Sparkplugs etc .) ,dont wait for 7000+Kms to change the Oil, i do it almost every 1000/1500km sometimes even earlier so are Sparkplugs ,Trans Oil and so on .You need to stay on Top of the Car one step ahead ,LOL.I do all this just too do it not that it needs done, so dont get me wrong ,i like to prevent where ever possible .
All the Best .
Ciao
There must be more Troublefree runners here ,I hope . :thumbsup:
 
#16 ·
that's why your car accelerates so slow compare to a 600 LOL
Where ever this comes from Beats me ,LOL ulflei.:thumbsup:
 
#9 ·
Hey don't worry, you have nothing to be alarmed about. I have a customer with 96 S420 246k that's treated like a truck, even his car drives like new minus the swaybar links on one side. And, the front LCA bushings, are orginal, I kid you not, must be the lower suspension, which by design limits the over all travel of it. Enjoy it!

I know what you mean, my car is pretty much up to spec now and I'm bored, maybe I'll just buy another one.:D
 
#11 ·
Hey mine is a 93 s 400 (same engine) with 83 k second owner miles (me) on it. I bought it from first owner in 1995 with 29k on it . Had no problems except for filling up a/c with refrigerant for the last 4-5 years . Now I have problems as posted in this thread.

Whats the plane fare Seattle / NYC . Maybe you can fly over here and help me get mine running great again. Congrats on a car thats running like it should , but dont jinx it by saying it too much LOL
 
#20 ·
well just goes to show everybody that life is good but its not always fair.. those who do not want the problems end up having dozens of them... my first year of ownership i repaired 2 sideview mirrors, a fautly pse pump, a faulty headrest gear, faulty headlight washer, bad lca bushings, replaced spark plugs, replaced fuel and air filter, replaced a bad automatic transmission socket, swaybar bushings, swaybar links, replaced a 9year old battery....on the 1st year of ownership!!!! on an 18k km car. can you believe that!! and those that do not have problems replace oil every 1k km have so much money they dont know how to care more for their cars... hahaha just the irony of life... but of course whatever works for each one let it be...
 
#24 ·
it looks like you need to come done to southern california and help me take care of my valve cover gaskets, cam seals, powersteering seals and hoes and i'll take care of the oil change. :)
 
#27 ·
s420 1998 36K miles. need diagnose coolant leak - I think

car started overheating. Has been great for years. If air conditioning isnt cooling, could that be because the car itself is overheating? AC shuts down if car is hot? The gauge doesnt show overheating. Both fans were running and very noisy. Cant see any broken hoses. Felt all around to see where there could be a leak. Yes, there is coolant in the tank - for a car that was overheating so badly, surprised that there is still coolant.
In san diego area, dont have any idea of where to find a good reputable mechanic without losing your shirt. May have to start off with paying for diagnosis by MBenz. Please any thoughts? Thanks:confused:
 
#28 ·
car started overheating. Has been great for years. If air conditioning isnt cooling, could that be because the car itself is overheating? AC shuts down if car is hot? The gauge doesnt show overheating. Both fans were running and very noisy. Cant see any broken hoses. Felt all around to see where there could be a leak. Yes, there is coolant in the tank - for a car that was overheating so badly, surprised that there is still coolant.
In san diego area, dont have any idea of where to find a good reputable mechanic without losing your shirt. May have to start off with paying for diagnosis by MBenz. Please any thoughts? Thanks:confused:
My Suggestion is start a Brand New thread.

I can chime in with suggestions..

Martin
 
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