There are four wires which are attached to this one small assembly in the door that come out of the door is this for the window? I don't think its the switch because I replaced them fairly recently. Do i need a voltmeter to test the wires out though because i don't have one? Is there something else i could test it with?

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W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.