I've searched but couldn't find any hints/answers. Do you need a power connection for an ALDL cable? I had one made by our controls department (assumed they could read electrical schmeatics) but moates scan software doesn't connect? Any way to make sure a cable is good/bad?

 

Yes you do need power if you are using the MAX232 or the transistor interface. older computers used to send 12v to the DB9, this has become rare. so the easiest thing to do is to get 12v from the car to power the interface.

 

Where would I bridge the 12v source into? I have two wire coming from homemade cable, coming from my serial port on my IBM Thinkpad and going to the aldl port, one for ground and one for data. Where would I do this?