When my signal is on, the idle will jump up and down ever so slightly and the battery gauge oscilates back and forth with the signal lamp. Is this normal?

 

When your blinker is on you're usually stopped, right? So you're at idle RPMs (or lower if you have an auto trans, cuse then you're on the brake instead of in Neutral). The alternator doesn't put out nearly as much current at idle as it does at highway RPMs, so the blinkers bulbs are drwaing more than the alt is making. If you have other loads on (lights, stereo, AC, etc.) it's worse.

So it's not "normal", but it's not unusual.

 

Thanks, what is normal for voltage reading, mine is usually almost a8 volts, I thought 13.8 was normal, 17?

 

Same thing here.

 

13.8V is the minimum voltage required to charge a 12V battery.

14-16 is normal.
Toyota voltmeters seem to read high, mine says ~18V, but using a real DVM it's closer to 16V.