So pull the screw out and check it? It really shouldn't be very hard - I'm assuming you have the cam gear?

Yes, with a magnet, you'd probably want a large gap. You might consider the deal extreme ones, they are handy to have around the house anyway. They are sold for making batteries fit in the wrong size devices, but I use them all over the place.

If it were me, I'd wave the magnet in front of the sensor, and see if you get a signal. :-)
-Abe.

Yes, I have the stud/nut out. It's just that, not being metric, I'm having trouble matching it over here. I'm going to try a place I know tomorrow that always comes up trumps when I need unusual fixings etc. Hopefully that'll sort it.

If I wave a magnet in front of the sensor is that something that a DVM will read? I have a variable bench supply so checking it out shouldn't be hard. Actually I've always been tempted by one of these would be very useful for this type of thing.

Sure, I forget if it was two wire (it's likely 3) but you'll most likely see it floating, and short to ground when it's "on".

So, put a big resistor (1k?) on the "output" line to the supply voltage. Then read that output line, and when it's "on" it should drop to 0 volts, the rest of the time it should be at supply.


BTW, American threads are pretty easy - it's in threads per inch. Very likely it's a 4-40, 6-32, 8-32 or 1/4-20. The first numbers are just a size, you can look it up on any tap-drill chart, with metric equivalents. The 1/4 is a 1/4 inch, or 25.4/4 mm.

The second number is the number of threads per inch. So, measure out 25.4 mm, and count the threads. If you get ~32, it's 32. If you get ~40, it's 40. Etc etc, and it should be pretty obvious once you do it. Or send a pic of the bolt next to a ruler.

It's done. Tested the sensor using a bench supply off and then on the car before applying battery power and starting the engine. The whole thing looks very clean and neat, far better than having that Mk1 OEM CAS on the engine. Plenty of room at the back of the engine now.

For information the sensor picked up ferrous material up to about 4mm air gap, and up to about 11mm with the magnet (which I went with).

I'll put up pictures at some point soon.

Thanks to everyone for their help.

Would love to see pics.

Out of curiosity, did you get more sensitivity to the magnet with one polarity than the other?

Yes, in fact the sensor only seemed to work properly with one polarity. The side with the dimple on it worked, the other did not.

Pls. summarize what you ended up doing for posterity.

Will do. I've taken photo's so given a few days I'll get them posted with a summary.

I drove the car on Saturday morning. The engine ran fine 99.9% of the time but every 2 or 3 minutes it would momentarily hesitate and buck. Every time it did this WinTEC4 flagged an intermittent CAS error. Disappointing and not something I could live with, so I had another think about it during the afternoon and made some changes on Sunday. I removed the magnet as I did not have time to play with it further. I do not know whether the Hall sensor did not like the magnet or whether it was the size of the air gap or that the magnet required better alignment (on the bench the sensor acted a little strangely at times if it was not passed directly over the magnet or if the magnet was orientated in reverse polarity - it occasionally remained pulled to ground). So I made the decision to go with a more conventional ferrous tooth that I fashioned out of a small section of iron bar. I mounted that, made a new mount out of aluminium for the sensor that allowed for adjusting the air gap to about 1.2mm (well within the 4mm tolerance I measured on the bench) and for some adjustment of alignment.

Once the cam cover etc was re-installed I started the engine and let it idle for 10 minutes in the garage. No "intermittent CAS errors". I've since driven the car about 20 miles and it has not missed a beat, so far so good.

Could the magnet have been made to work? Probably.

My guess is it overpowered what the sensor was meant to read. Another case of "use what you're supposed to use for what you're supposed to use it for". I think an actual, bare, simple, hall sensor and magnet would work great, but since you bought a ferrous metal sensor, that's what to use. Way to go, glad it worked. I had the same issues till I worked out my circuit, and it's a world of difference doing it right. :-) Still want pics.

Been rather busy this week but have managed a short summary of the Hall sensor installation. I'll try and do a proper job of it soon - when I do I'll update the link here. Anything that I have skipped over then ask and I'll add it to the summary.