central locking ? WHY$

[drew@dyermaker.cs.uoguelph.ca (drew)]

My guess is they looked at what other Euro car makers were using (ie
Mercedes,) decided how they could improve on the reliability (introduce an
electric operated bi-pressure vacuum pump, where Mercedes used stored
engine vacuum - meaning central locking would not function after the
stored vacuum was depleted) and went with it.

The vacuum-based CL system in general is quite robust, IMHO the largest
failing with the VW implementation is the bi-pressure pump and its
integrated control elctronics, which like any electronics submitted to the
harsh environment of the back of someone's trunk/boot is wont to fail.

A recent parts car I acquired actually had an ant farm in the pump... :)

The simplistic nature of the system makes it dead easy to retrofit -
there's only one trivial wiring harness (from the driver's door electric
actuator to the relay plate power feed to the pump in the trunk,) plus
a handful of plastic vacuum lines with rubber connectors.  Provided the
rubber is  in good shape, and the actuator diaphragms are all good, then
there are no leaks and the system works well.  The vacuum actuators are
all the same part, which makes stocking spares easy too... :)

On the VW scale of engineering feats, I give it two thumbs up.  Now, let's
talk about the brain-dead power steering belt tensioner... :)

Drew

On Thu, 23 May 2002, Jonas K. wrote:

> On 5/22/02 7:50 PM, "Captnbr@aol.com" <Captnbr@aol.com> wrote:
> 
> > Does anyone know why VW decided to use a system like this?  It just seems
> > like it is so complicated and stupid. With all these airpipes and hoses and
> > stuff.  Why didn't they they just use simple electrical solenoids type things
> > for the locks? 
> 
> Up to speculation at this point, but I'd say most likely it was a
> reliability/cost issue. The system was designed almost 20 years ago, who
> knows how reliable or expensive those electrical solenoids were. Today the
> solenoids are not expensive, so they make more sense.
> 
> I actually think it's a fairly elegant system. Only when it malfunctions
> does anyone complain about it, and apparently most have lasted for at least
> 15 years. Pretty good for modern automotive standards. Wires, sensors, and
> solenoids would be just as complicated in terms of problem diagnosis,
> repair, etc. 
> 
> > I hate the sound it makes too ugghghhgghghhghghghghghgggploop. Everybody is
> > always like "what the F@#k was that noise"?
> 
> When operating normally, the pump should be nearly inaudible. It should also
> not run as long as your onomatopoeia (look it up) suggests. It should run
> only approx. one second.
> 
> Go to the pump, and disconnect the air connection. Borrow a vacuum pump with
> gauge from someone, or buy one, and pump a vacuum into the line going to all
> the solenoids. It should hold vacuum for quite a while, Bentley probably has
> a spec. 
> 
> The pump shuts off once it senses the proper vacuum/pressure, or after a max
> time (like 30 seconds). If there is a leak, then it will take longer to
> reach the vacuum/pressure, and the pump will run for a longer time. If the
> leak is big enough then the pressure will not be reached, and as a result
> the pump will run a long time. Finding the leak is not that difficult.
> 
> Also, the pump should be enclosed in a stiff foam casing, to insulate the
> sound. If that is gone, then it could be very loud, otherwise the pump is
> probably bad, and a replacement would help out lots with the noise.
> 
> HTH, 
> Jonas
> 
> 
> 
> 
> 
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Drew MacPherson - '84 Wolfsburg Edition Scirocco TurboDiesel