She won't start, getting a low voltage reading.

What is your question?

Putting the key in second position most lights come on, then in third position it gets a fast clicking noise and all the dials on the instrument panel go further down then they normally are and are fluttering very slightly in place at the same speed. ABS, check gage, check door ajar, seatbelt light, battery, service engine soon light stay on. Tried two keys, both do the same thing and also getting a low voltage reading. I haven't got a code, would this be a good time to go buy an OBD II? I have the manual, I'm reading everything front to back now to see if I can find out anything. Thanks so much in advance.