In the cars with vacuum/pressure pumps (W126, W124, etc.) the function of pump and actuators is a little different.
The pump, which is located under the right rear seat in the 124, and under the spare tire in the 126, is operated by an electrical switch on the driver's door lock. When you lock or unlock the driver's door, a signal is sent to the pump. The pump actually does both pressure and vacuum. Heres how: In the pump is a pressure switch. When the pump rotates in one direction, it produces a vacuum (lock) signal. When the vacuum reaches a preset value, the pressure switch shuts off the pump and reverses the polarity of the 12VDC going to the pump motor. When the door is unlocked, the pump turns on once again, but now it's producing pressure rather than vacuum. The system is pressurized and the vacuum actuators move out, unlocking the doors. When the pressure in the system reaches the proper level, the pressure switch once again turns off the pump and changes state (toggles) to the reverse rotation which will produce a vacuum (lock) the next time it operates. As a safety feature, there is a time delay on the pump motor which prevents it from running indefinitely in the event of a leak. After about 20-30 seconds, it shuts off. The pump is simple to test. Simply unplug it, plug the pressure port with a golf tee, and plug it back in. You'll hear it run for a short time and turn off with a very distinct "click", which is the sound of the switch reversing the motor circuit. You can even put a gauge on it to see it produce vacuum and pressure as it toggles back and forth. For the most part, the pumps are pretty robust, although I did have one fail on me. Troubleshooting on these systems is nearly the same as the 123 and earlier chassis', however, in this case you only have one supply line to each actuator, but the terminus for all the lines is still on the floor of the forward passenger compartment in the wire duct. Start with your vacuum pump at the line coming out of the pump, and move up to the passenger compartment floor from there. Again, this is a really, really simple system. You should be able to nail down the offending actuator within a matter of minutes. Dan --- Kevin Kraly <[EMAIL PROTECTED]> wrote: > Yes, Dan. The locks on my '83 300SD have been > inoperative since I've owned > the car. The pump goes until it times out (30 > seconds IIRC), but nothing > happens other than the fuel door locking (found this > out when attempting to > fuel up and had to open it manually). Luckily > enough, I did it quickly > enough and didn't have the pump attendant waiting > around. Here in OR, we've > forgotten how to fill our fuel tanks, hahaha. > > Kevin in Portland, OR > 1983 300SD 267Kmi, Ursula > > > _______________________________________ > http://www.okiebenz.com > For new parts see official list sponsor: > http://www.buymbparts.com/ > For used parts email [EMAIL PROTECTED] > > To Unsubscribe or change delivery options go to: > http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > ____________________________________________________________________________________ Food fight? Enjoy some healthy debate in the Yahoo! Answers Food & Drink Q&A. http://answers.yahoo.com/dir/?link=list&sid=396545367 _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
