[bobcowan]

I didn't buy their harnesss, I made my own. But I followed their instructions. I got a message from Matt at DIY this morning. And he told me not to follow the MS instructions, but told me to wire the Hall sensor a little differantly.

Previously, the instructions said to feed the sensor through the ECU, to get a 5v signal. Today Matt tells me the sensor should get a 12v switched feed. Fortunatly, I had a spare wire in the engine harness in case I wanted to do something like this in the future - something I did when I wired the car 7-8 years ago.

So, tonight I spent about an hour or so redoing the harness in the front of the engine. It really wasn't that big of a deal for me to do it. I could have done it in about 10-15 minutes, but I decided to take the whole thing apart, check all connections, re-wrap, and re-tie everything. Probably not necessary, but it made me feel better. By comparison, opening up the ECU and putting it all back together again takes about 90 minutes.

A VR sensor is simply a magnetic "switch". As the ferrous object moves in and out of range, it trips the "switch" and sends an analog signal. The analog signal goes in to the ECU, and through an additional circuit the signal is then modified to a clean digital signal.

A Hall sensor is a VR sensor with a microchip attached. The microchip uses power to modify the analog signal to a clean digital signal. In basic terms (that even I can understand), the additional clean up circuit is part of the Hall sensor instead of the ECU.

According to the people who built the ECU (and the people who designed it) experience shows them that the best results come with a Hall sensor on a VR circuit, without a pull up. So, that's what I'm using.

I did some more reading today, and have a couple of ideas. The sensors (VR and Hall) are quite sensative to the air gap. The instruction manual says it should be 0.75-1mm. Other sources say 0.5mm. DIY recommends 1.5mm. Again, some conflicting instructions. I'm going to try moving the gap up and down until I get a clean signal. I'll leave it where the signal is best, regardless of what the actual number is.

It was too late to run the engine tonight, but I'll try again tomorrow.