Help!!!... I just realized that my dad's s280's central locking pump keeps activating in 20 sec or so intervals... locked or unlocked... though nothing actually happens... locks stay as they are... backup antenas stay as they are and even the trunk latch mechanism stay put... they DO WORK properly when triggered... i just hear the pump running under the passenger rear seat... i confirmed it was the pump because the pump was hot.

can a small vacuum leak cause this? does the entire vac system need to maintain a certain pressure or lack thereof? coz if it does then it should be a simple vacuum leak... on the other hand... if it doesn't maintain a certain pressure, what could be activating it?

thanks guys

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85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

how is the climate control system? some of the cars use the pse pump(central locking pump) to supplement vacuum to the climate control system when engine vacuum is low, usually it comes on, but should not as frequently as you describe.
what i have seen cause it to act the way yours is usually happens when there is a leaking vacuum control servo in the dash, look at your pump vacuum connections and see if there is a clear vacuum line going to it, usually the supplemental vacuum hose is clear or light in color, i have usually cut the line and plugged both ends and see if this stops the pump from running so often, if it does stop it, keep in mind this is a temporary fix and the leak needs to be properly identified an corrected. and if it is let go the pump will eventually burn up,

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1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins

thanks for the speedy reply bro... i do not remember seeing a clear line... i will have to double check though...

offhand do you remember which nozzle the a/c vac lines go to? i remember seeing 2-3 letters per nozzle. thanks

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85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

You must have a leak in either the vacuum line used to supply VAC for HVAC when the engine does not produce any like in REST, or you have a leak in the lumbar section which provides pressure. They both have reservoirs and the pump is replenishing.
Transparent (P-) vacuum
Gray (p-) lumbar
There also could be a bad check valve on the engine side.

thanks for the reply bro... i temporarily plugged the P- nozzle at the pump and all is well again. never messed with the lumbar thingy anyway...

don't have the time and energy to do a thorough check of the vacuum lines right now... but at least you pointed me in the right direction. thanks guys!

important things are the locks and the trunk.

__________________

85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

The controls for my lumbar/orthopedic seat leaked on my driver's side, the pump burned up. IIRC the pump was around $1400 (dealer).

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Gone to the dark side

- Jeff