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#1
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Door Lock 300SD
I seem to be having a problem with my vacum system. I can lock the car without any problems but I run into problems when trying to unlock the car. I can use my keys to unlock the driver side door but none of the other doors unlock. If I try to open the rear passenger door it is very hard. If I open the front passenger door all the other locks unlock. This happens when the car is on or off. Any ideas what could be wrong?
I have read some other posts but the ones I have read seem to have slightly different problems. Thanks Amin |
#2
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It matters whether you have a W116 300SD (US 78-80), a W126 300SD (US 81-85) or a W140 300SD (US 92-93).
If it's a W116, it's an all vacuum system that I'm not familiar with. If it's a W126, the locks have a dedicated electric powered vacuum/pressure pump. I'd start by checking the key switch in the driver's door. If it's a W140, I can't help you. Sixto 91 300SE 87 300SDL 83 300SD |
#3
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It is a 126 body. 300SD 1982
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#4
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Check that the yellow wire going to the pump (in the spare tire well in the trunk) gets +12V when you turn the key to unlock on the driver side. Maybe simpler to check if the pump hums or vibrates when you turn the key to unlock. Should only go on for 2-3 seconds, I think.
It's curious that all the doors unlock when you unlock the passenger side because the US 82 300SD doesn't have wires to the pump. Central lock actuation from either front door and the trunk didn't start until 85. Sixto 91 300SE 87 300sDL 83 300SD |
#5
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If you have a bad Vac pump I have one on Ebay
Item#2404803659
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#6
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I have always unloced the car from the driver side door. The problem I am having is that the car is unlocking but I have to manually unlock the front passenger door and then all the others unlock. I checked the pump in the trunk and it seems to be working. An individual I know said that it is not working as well as it should. Could that be why I can lock all door and have problems unlocking. When I am manually unlocking the passenger and I do not hold on to the lock well it is sucked back into the locked position.
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