We have a 1998 C230 and the automatic door locks have stopped working. There is no response to the button on the key, nor to the button inside the car. The trunk is the same. Also the rear headrests no longer function. When the button on the key is pressed, the exterior lights flash and there is a very faint "click" from the PSE and thats all. A Mercedes service manager listed the fuses for us to check and they are all fine. We purchased a used pump over the internet (correct model number) but the situation is the same. All doors and trunk must be locked/unlocked with the hard key.
Is there anyway to bench test the PSE? Is there a relay specific for the PSE - I noticed one in the trunk on the same side as the unit?

Appreciate any and all assistance.