Mercedes Electric Door Lock Pump Location, Inspection and Testing: 1981 to 1985 W126 Chassis Only

If your pump is running and your door locks are not working check out Kent's full video manual available on W126 Door Lock Troubleshooting and Repair (where he goes over the entire system in detail). mercedessource...
In this free youtube video he covers pulling the pump and testing procedures on the bench for the early style pumps (with only one wiring plug). This includes the 300SD, 380SE, 380SEL, 380SEC, 500SEL, 500SEC. Sorry no video or instructions are available for the later pumps with two wiring plugs (1986 to 1991).