W220 top switches
10-22-2016, 05:21 AM
#1
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W220 S320, W126 380SEC, W111 220SE
W220 top switches
Can anyone advise me where the fuse supplying 12 volts to the top dashboard switches (ESP, hazard, rear headrests, airmatic height raise, etc) is on the W220? these functions aren't fused through the left or right front SAM modules, and my hunch is they are supplied via an electronic fuse located under the front passenger footwell, but I could be wrong. If it is an electronic fuse, it would be non-repairable, and it would be best to make sure that's the problem before ordering a replacement. A scan on my S430 shows up fault codes for the obvious; these switches aren't working. Previously water got in from the front cowl and seeped under the carpet, which may have knocked out an electronic fuse. All responses appreciated.
10-22-2016, 01:05 PM
#2
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I have no idea where the circuit protection is for the dash buttons.
However, "electronic fuse" is probably not really good terminology. Applicable circuits are computer-monitored. If a short-circuit develops, the computer detects the increased current draw and disconnects the circuit to prevent damage. The computer will then periodically apply minimal voltage to the circuit to detect whether or not the short-circuit still exists. When the short is no longer on the circuit, the computer restores normal electrical power to the circuit.
While it is possible (and even probable) that the water intrusion has caused damage, it is likely to be in the SAM under the right rear seat.
However, "electronic fuse" is probably not really good terminology. Applicable circuits are computer-monitored. If a short-circuit develops, the computer detects the increased current draw and disconnects the circuit to prevent damage. The computer will then periodically apply minimal voltage to the circuit to detect whether or not the short-circuit still exists. When the short is no longer on the circuit, the computer restores normal electrical power to the circuit.
While it is possible (and even probable) that the water intrusion has caused damage, it is likely to be in the SAM under the right rear seat.
10-22-2016, 07:51 PM
#3
I have no idea where the circuit protection is for the dash buttons.
However, "electronic fuse" is probably not really good terminology. Applicable circuits are computer-monitored. If a short-circuit develops, the computer detects the increased current draw and disconnects the circuit to prevent damage. The computer will then periodically apply minimal voltage to the circuit to detect whether or not the short-circuit still exists. When the short is no longer on the circuit, the computer restores normal electrical power to the circuit.
While it is possible (and even probable) that the water intrusion has caused damage, it is likely to be in the SAM under the right rear seat.
However, "electronic fuse" is probably not really good terminology. Applicable circuits are computer-monitored. If a short-circuit develops, the computer detects the increased current draw and disconnects the circuit to prevent damage. The computer will then periodically apply minimal voltage to the circuit to detect whether or not the short-circuit still exists. When the short is no longer on the circuit, the computer restores normal electrical power to the circuit.
While it is possible (and even probable) that the water intrusion has caused damage, it is likely to be in the SAM under the right rear seat.
this is where the water travels - along the red main battery cable to the rear sam. The problem could also be a corroded prefuse /distribution block where the battery cable attached in the front passenger footwell as shown:
10-23-2016, 10:45 AM
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W220 S320, W126 380SEC, W111 220SE
Thanks for the advice. Water did damage the rear SAM, knocking out the rear lights. It was replaced, along with drying out the carpets, and all the faults on the dash readout vanished, and the lights came back to normal. The new SAM fixed that problem, but the top switches don't work. Only solution now is to get it Star-scanned, I did a scan with a Carsoft i980, (a OBD2 scanner with fault codes for Mercedes) and that showed the malfunctions, but not the cause. The joys of owning a W220!
