mmmh, I don't think that will do: it's a motion detection device... designed for quite long distances (3-7 meters with "option" 0-3 meters...); plus it works with an output signal that we can't manage...
IMO we need something optical that works as a simple switch. Sort of the ones used to protect automatic gates.

 

Been there a few years ago after pulling the car out for the first spring drive. Started wearing a grove in the inner belt. Replaced belt, replaced sensor. Now I spin it by hand before each drive just to be sure.

 

I considered this a few years back when I repaired my sensor. I do think the
original little wheel is a very crude solution. In fact, I've had one fail the other
way, whereby the wheel gets stuck and doesn't trip the warning light even
when the belt snaps.

I was considering using a proximity sensor similar to the ones you find on
eBay (like this one).

I believe this sort of sensor doesn't require a transmitter/receiver setup.
It simply opens and closes the circuit depending if an object is in front of
it or not.

Some have a range of up to 20mm, which would be enough to keep it clear
of the belt, especially if you positioned the sensor closer to the pulley where the
belt would oscillate less. Additionally, many of the sensors are manufactured
for tough industrial use.

Lots of the sensors seem to operate within a broad range of voltages
(5v - 30v) so 12v should be perfect and it's readily available as the little
black fuse box is just to the left of the pulley sensor.

This should give a reliable warning system, which is solid-state and doesn't
require physical contact with the belt (so no wear).

 

An optical sensor in that environment is a non-starter and an inductive proximity switch requires metal. The Porsche sensor consists of a hermetically sealed cherry switch, a spring and a bearing. Its going to be tough (but not impossible) building something that simple, with better longevity and costing anything even remotely close.

 

What about capacitive proximity switches?

 

You might run into noise problems from the ignition system but give it a shot (just don't use the sensor mentioned above from eBay) if you can find one that will handle the engine compartment temperatures and the occasional water ingress.

 

Or use a single pulley conversion for alternator and cooling fan, if the belt breaks the no charging lights are the warning. No need for the belt sensor if this is used.

 

Simply PERFECT!

 

There is a down side to doing this i.e the alternator spins more slowly and therefore gives less charge, but unless you drive using full electrical load this is unlikely to cause any problem. Gain is simplicity and a few extra BHP....always nice!

 

I've been through three of them.

The original began to squeak, then failed. The replacement just came off the shaft it runs on, for the peened-over end of the shaft sorta lost the 'peening'. That replacement was installed in November of 2011 ... and died in the same manner on March 13, just as I got into town after a long drive into Minnesota to watch my daughter graduate from college.

Luckily I now know exactly what that red idiot light means, had a wire coat hanger to cut up with a Leatherman tool to wire the thing out of the way of the belt. Again, the peening failed.

So, regarding this solution to replace the bearing with one loctited in: my recollection is that the wheel has a plain bearing at its center that runs on the brass shaft - whose end is peened over to retain the wheel ... one can press that plain bearing out of the wheel? Or is the actual bearing surface not the shaft put a point further outboard, as it were? Then the replacement bearing is actually concentric to the shaft, so that it can be loctited to that shaft?

Enquiring minds ...

 

Has anyone thought to just make a metal idler wheel with a decent bearing to replace the original? Seems it would be simple - it's never the case that breaks, just the wheel as far as I can tell...

 

Well, boys & girls, I have (I think) solved the problem. Go look at this thread: "Fixing a failed sensor before it fails" in this forum.

Observations, critical comments invited.

 

The bearing doesn't appear to be the problem. The shaft that runs through it is merely pressed in, and it fails at the peened-over bit. I came up with a fix. Search "Fixing a failed sensor before it fails" where I have detailed photos & steps.

 

so is your running update an A+ on your project ?
Dan

 

So far, so good! Will keep an eye on it and report whichever way it goes.