1998 Mercedes S600 A/C code

Chris Technician Bryans Road, Maryland Posted   Latest   Edited  
Question
HVAC
1998 Mercedes-Benz S600 6.0L 5-spd—WDBGA57GXWA381367
B1427

Good morning everyone ! I have 98 S600 that came in for no A/C operation. I first hooked up the gauge and the system was low so I did a evacuation and leak down test. It passed so I went ahead and attempted to charge the system but the compressor would not come on. I figured I would have to clear a code for it being low so I went ahead and got the codes out of the HVAC unit. The only code I have is a B1427 which I can not find a description to. I have found a few code lists and the ones I have found skip over this code. I have tried to clear the code through the module and it never goes away. I have no yet disconnected the battery to see if that would clear it because I wanted to try to figure out what the code meant before I did that. If anyone has any info on this I greatly appreciate it.

Thanks Chris

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Robert Engineer
Durham, North Carolina
Robert Default
 

Hello Chris, Is the EC light on at the HVAC control unit? Certain software versions in this vintage had some odd fault code behavior. Depending on what version of the SDS software you were using it would mask certain codes from the user. Since there were some hidden codes the "erase codes" function was grey'ed out. The easy solution in the field was to disconnect another HVAC component that…

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Chris Diagnostician
Bryans Road, Maryland
Chris Default
 

Thanks for the reply Robert. So I was manually getting the codes out of the Hvac unit and that was the only code it was giving. Since that code would not clear and the compressor was not coming on I assume that code was keeping the compressor from coming on. I tried multiple times to clear the fault manually through the hvac unit but it would not clear. So I tried to see if I could jump out the…

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Robert Engineer
Durham, North Carolina
Robert Default
 

Be careful about jumping the low pressure switch. Check the wiring diagram. I think that has a refrigerant pressure sensor not a simple switch. If you not really careful you can blow stuff up. My guess is if you unplugged the "switch" set a code, and then cleared them you did what is written above. Great you got it going!

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Chris Diagnostician
Bryans Road, Maryland
Chris Default
 

yea I had just unplugged it and it had set a code. It still worked even with that code in there. I cleared the codes and it went away except the b1427 code. Thanks

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Billy Mechanic
Deming, New Mexico
Billy Default
 

Just a note from (learn from my mistakes) anytime I had a OBD 2 AC job the first thing is grab a factory compatible scan tool and scan all the modules. Then I would hook up gauges to get a complete picture. Majority of OBD 2 the compressor is controlled by the PCM due to unwanted compressor operation while under load. I got to the point I would keep Honda AC compressor relays in my box because…

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Chris Diagnostician
Bryans Road, Maryland
Chris Default
 

Your correct I should have plugged in a scan tool to look for other codes. I guess I was under the impression if i was manually getting codes out of the module that was really the only way to get codes. But you are correct there also could have possibly been a clue in the ECM Thanks

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