944S2cab
Member
The central locking on my 1999 W220 does not work. It does not work with the key fob, the dashboard switch or by turning the metal key in the lock. Other related things which do not work are the remote boot release, the locking fuel filler flap and the rear headrests.
I have read a number of threads on this and another forum and I have a good idea of how the system works. I suspected the PSE pump. I dismantled it and found a burnt-out motor. I bought a used pump on ebay and soldered the printed circuit board from my old pump into the replacement pump, to avoid having to get it coded to the car. The resistance on the solenoids in the replacement pump are either 31.5 or 31.6 ohms, so not far from the ideal reading.
Using a vacuum pump and a handpump on the air lines I can open and close all 4 doors and the filler flap but not the boot. I have checked the air bladders on the headrests and they seem OK. The lumbar supports on all seats expel air when the dials are turned to zero, so they are working normally.
With the PSE pump electrical connection in place the motor runs permanently when I shut the boot lid. This suggests the problem is in the boot circuit. I have glued the "hockey puck" actuator. Pressure applied to the black hose going into this causes the pin to come out almost an inch, so the actuator is OK. The white actuator for locking the boot lid moves freely under pressure, so I assume that is OK. I have inspected the solenoids in the locking mechanism. The soldered joints seem OK and applying voltage to each one causes it to click. The switch with the blue connector has minimal resistance when the boot is open and locked. Checking was not easy - I needed 3 hands! Using the fob boot release causes a click at the PSE pump and briefly shows 2 volts at the black electrical connector.
At this stage I ordered a diagnostic kit from Carsoft.com (not iCarsoft - my car is too old for that one). It revealed fault codes 1436, 1437, 1438, 1440 and 1442 i.e all the circuits controlled by the PSE pump. I erased the codes but I can't get it to generate any new codes to narrow down the problem. I don't know how long the pump has to run to generate a code; I left it running for 30 seconds only so as not to burn out the motor.
In this cold weather the door lock freezes and I have to heat the metal key to get into the car. I am running out of ideas. If anyone can suggest anything I have not checked it would be appreciated.
I have read a number of threads on this and another forum and I have a good idea of how the system works. I suspected the PSE pump. I dismantled it and found a burnt-out motor. I bought a used pump on ebay and soldered the printed circuit board from my old pump into the replacement pump, to avoid having to get it coded to the car. The resistance on the solenoids in the replacement pump are either 31.5 or 31.6 ohms, so not far from the ideal reading.
Using a vacuum pump and a handpump on the air lines I can open and close all 4 doors and the filler flap but not the boot. I have checked the air bladders on the headrests and they seem OK. The lumbar supports on all seats expel air when the dials are turned to zero, so they are working normally.
With the PSE pump electrical connection in place the motor runs permanently when I shut the boot lid. This suggests the problem is in the boot circuit. I have glued the "hockey puck" actuator. Pressure applied to the black hose going into this causes the pin to come out almost an inch, so the actuator is OK. The white actuator for locking the boot lid moves freely under pressure, so I assume that is OK. I have inspected the solenoids in the locking mechanism. The soldered joints seem OK and applying voltage to each one causes it to click. The switch with the blue connector has minimal resistance when the boot is open and locked. Checking was not easy - I needed 3 hands! Using the fob boot release causes a click at the PSE pump and briefly shows 2 volts at the black electrical connector.
At this stage I ordered a diagnostic kit from Carsoft.com (not iCarsoft - my car is too old for that one). It revealed fault codes 1436, 1437, 1438, 1440 and 1442 i.e all the circuits controlled by the PSE pump. I erased the codes but I can't get it to generate any new codes to narrow down the problem. I don't know how long the pump has to run to generate a code; I left it running for 30 seconds only so as not to burn out the motor.
In this cold weather the door lock freezes and I have to heat the metal key to get into the car. I am running out of ideas. If anyone can suggest anything I have not checked it would be appreciated.