Voltage Question - How much?

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

Alright I got the alt off. I read continuity from the case to the fld terminal and from the grd terminal to the case. I also read continuity from the fld terminal to the grd termimal. One thing I am not sure of is the grd termimal. That termimal had the green wire on it and would always read continuity to the case because it is screwed to the case. I am confused which readings I should have continuity on. At this point all I know is I have continuity on everything. As of now I didn't take the alt apart to look inside. Is that my next step and if so what termimal to what should I not read comtinuity on. Thanks for all your help.

I was thinking we were dealing with a '70 up style alt with 2 male field terminals? If so that is a closed loop field circuit in the alt with the 2 male terminals being the ends of that loop & it cannot have continuity to ground. If it has 1 field terminal (69 & earlier type) then that male terminal will have continuity to ground since the other "grn" brush is grounded (there will be some total resistance from the male terminal down & in/around the circuit then out to the case with the "grn" brush being grounded to the case with you haveing the ohmeter leads on the male terminal and the case.

This is on a 71 Cuda. Is this possibly the wrong alt?

You have the flat reg with the triangle connector with a blue and a green wire to that connector? If so that is the later (70 & up) system & requires an alt with 2 male field terminals in addition to the large "batt" terminal of course. The blue and green wires from the reg would go to the 2 alt field terminals & (switched 12V) from the bulkhead also T's into the blue wire somewhere there but I forget where so that the alt & the reg both get fed). If the original alt died & they replaced it accidentally with an earlier one (with only 1 field terminal) they would have noticed the extra field wire with no place to be plugged in on the alt I would think

It is the regulator with a triangle connector and it has a blue wire and a green wire coming off of it. The alt has the large stud for the battery and it also has two male connectors. One is marked GRD and had the green wire attached and the other one is marked FLD and had the connector that has a blue and also a dark blue with white tracer on it. I am not sure about the continuity readings. the GRD terminal will have continuity with the case of the alt because the male terminal is screwed to the case. Where shouldn't I be reading continuity, between the FLD and the GRD terminals?

There should be continuity between the 2 male terminals (that's a closed field circuit loop inside the alt) but no continuity between either of the 2 male terminals to the case (that circuit ain't (& should not be) grounded to the case

Well it looks like my next step is to go to the parts store and pick up a new alt and make sure it doesn't have a GRD terminal that is screwed to the case.

I wonder if someone grabbed an extra brush assy with the male lug on it & installed it on an earlier alt (in place of the "fld" brush holder with no male lug) & did not use insulating washers on the bolt to keep the brush from being grounded. This would have allowed current to come in from the blue hot wire on the other male terminal then go in/down/around the field circuit & out to the other brush & be grounded to the case right at the other brush which would have full fielded the system. If that's what happened actually that would have worked if they had put an insulating washer (might need 2) on the mini bolt that fastens that brush holder to the metal mounting nub on the alt case (which is grounded) so that that brush ain't grounded right there to the nub (case). Might check that out & might save you a trip.

I just looked up Cuda alternators on Ebay to get a look at the back of one and I see what you are saying about the two male connectors not being grounded to the case. I tried to attach a picture of mine and the file was to large but mine is defiantly different. I bought it at a local parts store about a year ago. I would have to say at this point they sold me the wrong one. It is defiantly hard to find a good local parts store that knows anything about old cars. At least this time (thanks to you)I will know what to look for and test before I leave the store.

I dont remember if it is the brush holder that is insulated or washers on the bolt is what insulates the brush from the case or both (been awhile since I did brushes). If you are going to purchase a new alt you might ask for one for an 85 M body (I believe) which is 78 amps rated. Might have the parts guy pull it & your choice & if they mount the same & the center divider is the std thick one & the price is right it'd make sense to go with that one

I picked up my new alt yesterday and the back looked different. Both field terminals (not one field and one ground)were insulated. Rushed home today and installed it, what a big difference. The headlights and dash lights don't dim, the radio doesn't act up, the autometer amp gauge don't move around, and I no longer have a higher voltage at my battery that fluctuates. It holds nice and steady. A big thanks to all, especially RapidRobert for all you help.