All original 1.7. Recently noticed voltage reading low (10.5) and red light which indicates emergency brake engaged flickering. I replaced the E brake trigger switch not thinking the two issues were related which did not not solve the flickering. Also noticing a periodic hesitation when driving. Any thoughts on what might be causing these symptoms and if they are related? Thanks.

10.5 volts is too low. Where are you measuring? Do it at the battery. Check with the motor off and then running. Must be higher when running 13.5 or so. Check all fuses

When you say the brake warning light is flickering, do you mean irregularly, or flashing like the turn signals flash?

--DD

Honestly wouldn't be worried about a handbrake light,time to address low voltage in your system ,soon but not later you will have insufficient voltage to your coil and more importantly your starter won't turn over,DON"T take voltage from any where but the battery,you should have 12 + volts at rest and 13.4 to 14.4 under full charging load.
Do you have a working charge light?

+1. My GEN light used to come on and the center console voltmeter showed low voltage, but I had 13.5V at the battery with the car running. Bad grounds/bad connectors are common with our cars (I eventually removed the center console after I cleaned up all the connections.)

I have a corollary problem: my GEN light is on bright-ish at idle but dims as RPMs increase. Good voltage at the battery but of course lower voltage at lower RPM. So the GEN light is in INVERSE indicator...!

Need to break out the wiring diagram and figure out what's going on there. Good battery voltage at the fuse and the input wire, need to ring the wiring to see if there's some kind of connection problem to the alternator.

Isn't this as it is designed? A warning light for low output that disappears as the alternator revs increase and output come up to proper voltage.

Ugh, I wrote that backwards: it's actually DIM at idle and BRIGHTENS as RPMs rise...

There is some great information in this thread:

Alternator thread

Jim

That Post #15 is a gem.

Ok i have 12.9 at battery with car not running. When running voltage jumps all over the place from 3.5 to 13.5. In response to Dave's question it flickers irregularly. I have read the thread recommended by Jim as well. I'm thinking voltage regulator at this point (hoping anyway). If that doesn't cure the problem will proceed with testing the alternator as suggested.

That cannot be correct. The voltage cannot go below 12.9 when running. I suspect a meter or a connection at the meter. Maybe your meter or the leads are bad. Auto ranging meters can cause issues. You may have a bad alternator but I suggest trying a different meter first

Flickering irregularly tends to indicate a poor connection somewhere.

--DD