My battery is not charging fully. I am only getting 12.8V to the battery
@ 1500rpm. I checked the alt the way plaidside said to. Everything checked out fine. So I took the alt to Autozone they checked it also.
I bought a new alt and installed that one same reading 12.8.
I changed the votage reg. no change after that. What else could cause the problem?

Shemp

 

If you are measuring voltage at the battery posts and not the cables it could be you have corrosion at the battery cables. Proper charging voltage should be up around 13.8-14.2V..

 

I checked the cables & connections and everything looks good. I
had the battery charged and checked and it is fine also. When I
checked for voltage @ the battery it was 12.8 and when I turned
on the lights it dropped way down to around 11.8 or 9 and continued
to drop from there.

Shemp

 

I had, a while back, 18.2V at the battery. Thought it was the alternator. Had it checked, it was good. Turned out to be my multimeter I was using. Bought a new one, and everything was fine. Just a thought.

 

I checked it in OC at corvette week, that is where I got the new alt &
volt reg. I had to buy a new meter because I didn't have one there. I
checked again when I got home w/ a diff meter still same results. I put my old alt back on and checked again still the same. I did everything
that Plaidside said in his thread. I have a new wiring harness also. It
was working before when I installed the alt and I haven't done anything since then.

Shemp

 

Shemp,
Are you saying it was working after you put the new harness in? Did you put a new alternator in and then it stopped working after a while?
Did it stop working after you changed anything?
Try this; connect the positive lead of your voltmeter to the positive post of the alternator and the negative lead to the negative lug of the alternator. Start the car and bring the RPM to 1200, put the head lights on to load the system. Do you have a voltage reading?
If you have more than 1/2 volt you have a high voltage drop.
This test is to see if there is any resistance to current flow from the alternator output to the battery.
What is the state of charge of the battery? Use a digital voltmeter to check it. A fully charged battery without a surface charge will read 12.66v.
If the battery has a very low state of charge the voltage at the battery will be low until the battery is fully charged. Think of a seesaw, if the battery state of charge is low, the alternator amperage output will be high and the charge voltage reading at the battery will be low. When the battery voltage starts to rise as it is being charged the amperage output will start to drop.
On these low amperage units the voltage and amperage cannot be high at the same time.
One goes up the other goes down.
If all my tests are good that you read in my article then I would substitute a good known battery. Yours could be sulfated which would prevent a normal charge rate.
Joe

Joe

 

It was working after I put in new alt then I noticed a battery drain
after a while. The battery (Optima red top 3 yrs old) was fully charged
and checked. I drove home Sat. nite w/ the lights on, I don't normally
drive it at night. I stopped for a beer came out and it was dead.
I will try what you described tomorrow and let you know what I find.
I just find it strange I'm getting the same readings w/ new alt & volt
reg as I was w/ the old ones.

Shemp

 

Shemp, I realize this was quite awhile ago but I'm having the exact problem with my 65 BB. I replaced the alt & regulator only to get the same 12.3 vdc reading. Did you every figure this out? Would be appreciated if you did and what caused it. Thanks

 

Check the connection of the wires and terminals inside the gray plastic connector on the back of the alternator; they're famous for fatigue failure, which will prevent the alternator from charging.

 

JohnZ, My 65 BB is having charging issues. I ran some alt/regulator tests as posted by one of the other members on this forum. I have 12.26vdc at the batt stud on the alt and that comapres to the voltage at the battery, Next I checked continuity of all the wires from the alt back to the regulator, all was fine. I've replaced the alt and went to a SS reg. When I start the car, the voltmeter just stays at battery voltage even when turning lights on.
What I did notice is that the battery was completely dry, it got cooked probably big time. I also found that the "F" (blue wire) and "R" terminals on the plastic plug were reversed. When I change them back to what they should be, the alt started charging according to the voltmeter across the "batt" terminal & ground on the alt. However, as I accelerated the engine, the volt reading kept going higher and higher with rpm gain, got to 18v and I shut her down. Could the battery have a dead/shorted cell causing the alt to continuously charge at a much higher rate?

 

If you let the battery go dry, go get a new battery as that one is now deceased

 

Just reminded me of what happened last month after firing up a car that had sat for six months and before that a year. At first it was charging 12.8-12.4 and so on for about the first 40 minutes, and then started to rise until it was charging normal at 14+ volts. It seemed to me the brushes contact area might have had a little corrosion, and had to be run to get a clean contact.....?

 

'bout 25 years ago I was having an intermittent charge/no charge problem on my 65 roadster. I was lucky enough to be looking under the hood when I saw sparking inside the insulation of the blue wire on the two wire connector. Clipped and spliced the blue wire and problem solved. With 40+ year old wires, you gotta be ready for ANYTHING. Check continuity on every wire to the charging circuit with an ohm meter. Don't take anything for granted.

 

I've been very thorough in checking all the continuity of each wire related to the charging circuit and doing a visual inspection. Short of ripping the entire harness apart so as to get a good look at the condition of each wire, that might be the last straw. I'll replace the engine harness ASAP. So far, all checks out good. How the "F" & "R" terminals got crossed, not my doing but the bubba before me. Surprisingly, my car didn't catch fire or the battery explode. Looks like I'll be buying a new battery tomorrow !

 

Probably not the cause of any of your problems, but I had a 1960 Corvette which gave me starting and charging grief over a period of many years. A number of "professionals" tried a lot of solutions over those years (new batteries, new/rebuilt generators, new voltage regulators, new/rebuilt starter motors and/or solenoids). Yet, I continued to have starting problems due to weak battery charges. Finally, I was doing some restoration work on the instrument cluster and found the connections at the amp meter to be corroded. Apparently, the charging current flows through the amp meter and enough was getting through for marginal battery performance. A check for corrosion at all of the connections might be worth the effort.

 

SubVette599, ironic you mention this. I was looking at the wiring schematic for my 65 and noticed how the ammeter was connected in the circuit, figured this would be yet another place to check.
Thanks for the input to everyone. That's what makes this forum great to be part of, all the many years of experiences that everyone can draw on....GREAT! For me, it's a learning playground

 

Yes, the ammeter in these old cars is in series with the car's entire load (unlike some later models) which is also a good reason why its the perfect place to stick in a 30 amp fuse to protect basically all of the car's wiring.

 

On a '63-up, whether the battery gauge (it's not an "ammeter") is connected or not doesn't affect the function of the charging system - it's only an indicator of whether current is flowing TO or FROM the battery.

C1's are different - they have a real ammeter that's in series with all the electrical loads, and is the power distribution point from the battery for the whole car.

 

Ahhhh, old cars are so much fun....it's a work-in-progress everyday. Getting a new battery today so hopefully, the charging woes will be over! Frankie the Fink, we're practically neighbors, I'm down the road in Windermere, I go to Mosaic Church in Oakland.

 

Well guys, after doing the testing to the alt/reg/battery circuit and after replacing a spent alt, bad regulator and a cooked battery, I'm still no further ahead!
I installed a new Die Hard Gold battery today with 12.96 VDC. Hooked up my voltmeters to the alt wiring and one to the battery terminals to watch voltage. I started the car and the charging began at 13.2 but the higher the RPM, the higher the voltage, all the way to 19+. I shut the engine down and started running all the tests all over again. I ran continuity on all wires to and from the alt back to regulator. The "F" terminal (dark blue wire) was good, the "R" terminal (black/white wire) good, red terminal was good also. I found that my #4 wire in the voltage reg plug (black/pink wire) has continuity with any ground I touch. I disconnected the firewall connector and had continuity from regulator to firewall connector pin. However, no ground condition in the engine compartment. Does anyone know where the BLACK/PINK wire goes once it crosses under the dash? Apparently, something inside the car is causing a ground condition which somehow keeps my alt in the high charge mode.