Re: 83 SD Central Locking Gremlin

On my '83 380SEL the locking is controlled by vaccum pump in trunk by spare tire. The drivers door lock operates vaccum/pump during lock/unlock for short time. On mine, centeral locking was not working well due to leak in
passengers door lock. Can hear air excaping. The gas flap and trunk work great but to lock rear doors must have passenger's door locked first. Experiment with locks to see which are leaking. I bet the fuse is a red herring. Getting door apart to replace vaccum lock is not easy.
-Kent
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<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> The vacuum route (by distance) is, starting from vacuum pump in the trunk, fuel door/trunk lock, front passenger door, right rear door, driver door (if front passenger door can lock/unlock others, but I think 83 is not equip. like that), then left rear door at last.&nbsp; The routing is not on a single tube.&nbsp; There are many branches but the above is usually the sequence each one operates. <p>The main branch is under front passenger carpet.&nbsp; That is a 4-way branch, coming from fuel door, going to both right doors and to left of car.&nbsp; A 3-way branch is under driver carpet, coming from right of car, going to both left doors. <p>I would suspect either a leaking door element or a dying pump.&nbsp; Start from everything unlocked.&nbsp; Use a hand vacuum pump to replace the electric pump.&nbsp; Can you lock all doors by applying vacuum?&nbsp; Can the vacuum hold for at least a few minutes?&nbsp; If yes to both questions, the pump is dying.&nbsp; If no to either, there is a leak.&nbsp; Now go dig under the front carpet.&nbsp; Unplug tubes from the branch then apply vacuum to tube.&nbsp; Can you lock door one at a time?&nbsp; The vacuum should hold for a long time if the element is good.&nbsp; Note that there may be multiple leaking so do a thorough test.&nbsp; Also, hand vacuum can only lock.&nbsp; It is the air pressure (by the electric pump) to unlock. <p>Kent_dieGo wrote: <blockquote TYPE=CITE>On my '83 380SEL the locking is controlled by vaccum pump in trunk by spare <br>tire. The drivers door lock operates vaccum/pump during lock/unlock for <br>short time. On mine, centeral locking was not working well due to leak in <br>passengers door lock. Can hear air excaping. The gas flap and trunk work <br>great but to lock rear doors must have passenger's door locked first. <br>Experiment with locks to see which are leaking. I bet the fuse is a red <br>herring. Getting door apart to replace vaccum lock is not easy. <p>-Kent</blockquote> </html>
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Excellent info. I now strongly suspect the pump. Starting with all doors unlocked and turning the key in the driver's door, only the rear doors end up remaining unlocked. Based on what you're saying about routing, it would take a simultaneous two-failure scenario at a minimum for that to have resulted from leakage, while a dying pump is a feasible single-point failure. Much appreciated.
BTW, you're correct - only the driver's door opens everything else on the 83 model.
The vacuum route (by distance) is, starting from vacuum pump in the trunk, fuel door/trunk lock, front passenger door, right rear door, driver door (if front passenger door can lock/unlock others, but I think 83 is not equip. like that), then left rear door at last. The routing is not on a single tube. There are many branches but the above is usually the sequence each one operates. The main branch is under front passenger carpet. That is a 4-way branch, coming from fuel door, going to both right doors and to left of car. A 3-way branch is under driver carpet, coming from right of car, going to both left doors. I would suspect either a leaking door element or a dying pump. Start from everything unlocked. Use a hand vacuum pump to replace the electric pump. Can you lock all doors by applying vacuum? Can the vacuum hold for at least a few minutes? If yes to both questions, the pump is dying. If no to either, there is a leak. Now go dig under the front carpet. Unplug tubes from the branch then apply vacuum to tube. Can you lock door one at a time? The vacuum should hold for a long time if the element is good. Note that there may be multiple leaking so do a thorough test. Also, hand vacuum can only lock. It is the air pressure (by the electric pump) to unlock. Kent_dieGo wrote: On my '83 380SEL the locking is controlled by vaccum pump in trunk by spare tire. The drivers door lock operates vaccum/pump during lock/unlock for short time. On mine, centeral locking was not working well due to leak in passengers door lock. Can hear air excaping. The gas flap and trunk work great but to lock rear doors must have passenger's door locked first. Experiment with locks to see which are leaking. I bet the fuse is a red herring. Getting door apart to replace vaccum lock is not easy. -Kent
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