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1994 s600 coupe
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685 Posts
Discussion Starter #1
so I tried to use the built in diagnostics in the HVAC to check for codes, temperatures.
I can get the system to tell me the temperatures,
but when I hold the 2 buttons in simultaneously to read codes,
it doesn't go into code diagnostics mode.
does a 1994 S600C have this capability or not ?
I tried this below


RETRIEVE DATA:

Turn on ignition (run car)
Put both sides Temp settings at 72
Push and hold “REST” button till you get a 1 in the left side
Push the left “AUTO” button to scroll forward and right auto button to scroll back.
Let the car run 3 minutes before pulling data to ensure more accurate data
For AC diagnosis you only need to be concerned about codes 1 through 8

Code 1 = Inside Temp
Code 2 = Outside Temp
Code 3 = Left Core Temp
Code 4 = Right Core Temp
Code 6 = Coolant Temp
Code 7 = Refrigerant Pressure (This is the important one)
Code 8 = Refrigerant Temp


PULLING FAULT CODES

Switch ignition on
Set left AC/heater temperature control to HI
Set right AC/heater temperature to LO
Depress REST and EC switches simultaneously within 20 seconds of turning ignition on
Hold REST and EC switches for more than 5 seconds
Air recirculation lamp flashes
Depress right AUTO switch repeatedly. Note trouble codes
FF is not a code

What the codes mean:
003 B1226 In-car temperature sensor with blower
005 B1228 Heater output temperature sensor
006 B1229 " " "
007 B1230 AC evaporator temperature sensor
008 B1231 Engine coolant temperature (ECT) sensor
009 B1232 AC refrigerant pressure sensor
010 B1233 AC refrigerant temperature sensor
011 B1234 AC sunlight sensor
012 B1235 Heater intake air purity sensor
013 B1241 AC refrig pressure sensor, AC temp pressure sensor refrigerant level
014 B1416 Engine coolant pump motor
019 B1417 Engine coolant heater regulator valve LH
020 B1418 " " RH
021 B1419 AC compressor clutch
022 B1420 Idle speed increase
023 B1421 Engine coolant blower motor control module
024 B1422 Serial interface K1
025 B1423 AC heater valve block
026 B1424 AC heater air intake filter actuator
027 B1425 " "
029 B1429 Serial interface K2


RESETTING FAULT CODES:

In fault code mode press both “AUTO” switches simultaneously for more than 5 seconds (after last trouble code is displayed)
Once codes are cleared you will see display change to "d and FF"
Switch ignition OFF – All Codes are erased
 

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1994 s600 coupe
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685 Posts
Discussion Starter #2
when I try to Hold REST and EC switches for more than 5 seconds
Air recirculation lamp DOES NOT flash
nothing happens, with car running or not.
does the car have to be running anyway ?
 

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1994 S600 Coupe, 1995 S600 Coupe
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2,017 Posts
Use the procedure here:

Appears you need to press Rest and 0, not Rest and EC to get into diagnostic mode.

Also note that there are other key combos to get info other modes. All worked for me.

Jon
 

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1994 S600 Coupe, 1995 S600 Coupe
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2,017 Posts
The procedure you were referring to is for the 96 up style HVAC controls.

Jon
 

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1994 s600 coupe
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685 Posts
Discussion Starter #6
just went through the codes, there was dozens of them, deleted them all, and only 2 came back.
rear seat controller, and charcoal filter
 

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1994 S600 Coupe, 1995 S600 Coupe
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2,017 Posts
Well, you don't have a rear seat controller, so you can skip that. The charcoal filter is the huge one, only used if you activate it. Many hundreds of dollars , buried deep, and only available from Mercedes.

Jon
 

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1994 s600 coupe
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685 Posts
Discussion Starter #8
is that the filter above the blower fan, under the hood, under cowl cover ? if so I cleaned it already
 

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1994 S600 Coupe, 1995 S600 Coupe
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is that the filter above the blower fan, under the hood, under cowl cover ? if so I cleaned it already
No. Somewhere on here is a post with a diagram of the HVAC system showing it. It's only activated when you press a switch on the console. You cleaned the fresh air filter.

Jon
 

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1994 S600 Coupe, 1995 S600 Coupe
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2,017 Posts
Found it. The filter you cleaned is 9 in the diagram. The charcoal filter is 10. You have to remove the fresh air intake, the wiper assembly, then there is another cover to get to it. Mercedes says to use a vacuum pump to compress a seal to get it out.


Jon
 

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1994 s600 coupe
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Discussion Starter #12
the backside/bottomside of the fresh air filter in my car, was covered with a layer of embedded charcoal as well.
the replacement filters I looked at, lacked the charcoal layer, so I re-used the old one
I would not want to change that embedded charcoal filter
 
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