[wamnram]

The original poster asked: Why does polarity matter to some Volt meters/testers?

Answer: Because that is how some of them are designed. I believe specifically the probe he was using. Also, positive voltage is not the same as negative voltage.

34Fordy stated: My Fluke 78 meter reads DC current plus or minus depending on where I place the probes. On AC current it reads the same both ways, not plus or minus as it is alternating.

Reply: Because your Fluke is designed that way.

JayChicago: I think I read that solenoids don't care how they are hooked up. I think that is strange. It's an electric magnet. Why would it not be polarity sensitive? Why would it not pull the other way?
Today 02:21 PM,

Answer: Because a solenoid creates a magnetic field that draws an iron rod into the field. It does not matter the polarity of the field because the rod is not polarized, it's just a piece of iron.

Rockfla: IF it polarity can flow two ways THEN why not make all electronic test devices work both ways???

Reply: Nowadays, almost all electronic devices, especially meters, are designed and built to work both ways. The older a device is, the less this is so.

Hopefully this answers some questions without going too deep into electrical/magnetic theory. I don't want every one's eyes to roll up into their heads while muttering WTH? (Lawson, you da man!)