Now that I have replaced the alternator in my Coronet, my volt meter is reading about 12 volts at idle, and up to 17 when the rpms are up.

Is that too much? I think I may need to change out my voltage regulator.

Thoughts?

Anything over 15V (ideally 14.5V) is too much. Your regulator is toast OR you may have a grounding issue. Make sure the VR is grounded VERY WELL to the body with ground strap and the alternator is as well. If there is a disconnect between the VR and alternator, the VR will not be able to 'sense' the alternator's output and will be rendered useless giving you high voltage.

X2 what CJ said, you're full fielded right now. Do NOT drive it until you solve it & if you have to drive it then pull the reg plug so it ain't charging at all. running the batt down some is FAR less damaging than having 17 volts going thru the system

Where are you measuring? If that is at the battery terminals, it is too high. If it is at an add on voltage meter, double check with a voltmeter at the battery. I would believe a test meter over any add on volt meter, even the Harbor Freight ones.

Craig

Yes...I'd double check at the battery

I'll double check at the battery before I do anything. I have a bunch of wiring and such to check as well - never trust the work of an unknown previous owner!

Are you using the 1 field wire alt with the old mech regulator or the 2 field wire with the electronic regulator ? Ron

1 field alternator and the old mechanical voltage regulator.

Thanks. I even have one sitting on the shelf here.

13.8-14.2 is where I like to see it.

Put in the new voltage regulator and now it's at 13.8 with 2000 RPM.

Thanks all!

I just read this post and it is perfect timing. I was coming home from a show at night and got on the gas and the headlights got bright and one of them burned out. The next day I took notice that my shift light for my tach started staying on. I did all the tests you listed and I have very low ohms and read 0 volts from the battery neg to the alt case but with a meter on the battery it reads up to 19 volts as I bring the rpms up to 3000. Does this pin point my problem to the voltage regulator?

Highly likely. 70 up system? Pull the triangle connector off of the reg & bring the RPM's up & if there's no charging then yes the reg. But do check the reg ground & that the alt brush/brush holder under the green wire terminal ain't being grounded to the alt case. Do NOT drive it till you fix it or if you do have to then pull the triangle connector so there's no charging

I am not sure what is going on. I pulled the connector off of the voltage regulator and as I bring the rpm's up the voltage still goes up. I also have a autometer amp meter in the car and at idle it reads around 0 and goes up between 45-60 as the rpm's go up, I am not sure if that means anything.

The alt has 2 field terminals right? (blue/green wires-70 up system). Pull the green wire connector off of the alt field terminal & at that stage the alt is recieving fire via the blue field wire & if charging then the field circuit is being grounded (full fielded) inside the alt to the case which includes the green wire brush/brush holder. Good visual on/in the alt to see what's grounded that shouldn't be. Pull both field terminals & see if either male field terminal has continuity to ground (should not) & might see how many ohms you have between the 2 field terminals them selves as you spin the alt by hand (there's a spec for that) but I think you'll find something wonky before you get to that. With the alt field terminals plugged back in if it's full fielding with the reg connector plugged in & still is when you pull the reg connector then either the alt is grounded as previously described or the green field wire between alt/reg is grounded somewhere between the alt & the reg. EDIT until we solve it if you have to drive it pull both field terminals off of the alt so that it DOES NOT overcharge. running the batt down 1 time like that (which is no different than leaving your headlights on for a bit which ain't a dealbreaker) is FAR less damaging (to the batt) than what full fielding will do (to the batt & the rest of the system) and when fixed do charge the batt back up with an outside battery charger rather than letting the car do it as you drive

This is on a 70 and up system. I pulled the green wire off the alt and the wire is not grounded between the alt and the regulator. I didn't start the car to see if it was still showing 19 volts but I also pulled the blue wire off the alt and checked continuity between the terminals and the alt case and I got continuity between the case and both terminals. This sounds like we have it narrowed down to the alt? As soon as I get home from work tomorrow the alt will be coming off to look for the grounding issue. Thanks for your help and hanging with me through this.

Correct, there should not be continuity in the alt internal field circuit (from male field "green"terminal end to male field "blue" terminal end) to ground. Eyeball the brushes/brush holders & see if you see anything touching there