System voltage is low - Battery not charging

[SPF Required]

In addition to my radiator issue, I discovered my battery is not charging in my ‘68 300 either.

I went for the easy fix and got a solid state voltage regulator. No luck! Volts are still between 11.8 and 12.2.

Went and got a remanufactured 55 amp alternator at the local Napa, installed it and still no change. Voltage barely goes above 12.

This is just about the capacity of my skills, but open to any suggestions you folks my have.

Thank you!

P.s. I have done the under hood and ammeter bypasses a while back (thank you @cbarge )

 

[FURYGT]

Have your battery tested.

 

[SPF Required]

Have your battery tested.

If the battery is bad, would that explain the low voltage in the system when the car is running?

 

[CBODY67]

If the battery has a flaky connection between the cells, or even a weak cell, it can compromise the ability of electrons to flow into the battery itself.

It might be too late, but have you cleaned the battery terminal posts and the inside of the battery cable terminals? A little bit of grunge there CAN cause issues.

CBODY67

 

[SPF Required]

have you cleaned the battery terminal posts and the inside of the battery cable terminals?

I will give them a scrub tomorrow, but visually they are pretty clean.

I’ll also check the voltage output at the back of the new alternator and see what the voltage is there too.

Thank you!

 

[rags]

If the battery is bad, would that explain the low voltage in the system when the car is running?

yes if it has a shorted cell. check the water level. if it has a low cell, it's shorted. if it's a sealed case but made of white plastic you can shine a light on the side of the case and see the fluid level through the plastic.

 

[HWYCRZR]

Put a regular charger on your battery. Sometimes with a bad cell, the charger won’t even work. Or it will charge up and show good voltage, but a few hours later it will drop. Or once you have it charged turn on your lights and see how fast the voltage drops (ignition off)
Or just take it to a Napa or autozone or oreillys or other battery place and have it tested. Recommend you charge it first.

If it’s over 4-5 years old with intermittent use it seems they can turn to junk overnight.

 

[GTX WON]

After checking your battery, check the large gauge wire on the back of the alternator and make sure it has 12 volts.
If not follow that wire and see if you have corrosion or a break in the wire.

 

[rags]

'68 should have a single field alternator. while checking the voltage at the large wire, you could check for voltage on the field wire. then you would know if the voltage regulator is exciting the field.

 

[CBODY67]

A weak cell can charge just fine, but will quickly deplete when any load is applied.

Charge the battery fully, letting the charger "kick-off" on its own. Then try to start the car, with the lights on, and see what happens. Then reapply the charger, which will probably spike to full charge and stay there for an extended amount of time. If the load recovery time is short, usually not a battery issue but poor connections that need to be cleaned and re-secured.

Enjoy!
CBODY67

 

[rags]

Charge the battery fully, letting the charger "kick-off" on its own.

charging a battery fully and correctly, being able to read the charge rates (current) and voltages is an art. the 850 cca batteries we use in the diesels, if they are run low, have to be charged for two hours at a low rate, 5 - 10 amps at the very most, and allowed to cool for half an hour before they will test correctly.

 

[413]

Hey let’s check the wiring on the 55 year old car.

Get out your voltmeter:
Large black wire at alternator needs battery voltage at all times.
blue wire at regulator needs battery voltage with key on.
Check continuity of green wire from regulator to alternator.

Now disconnect green field wire at alternator. Voltmeter on the battery cables. Start engine and raise to 1200 RPM or higher, now briefly (3-5 seconds) apply 12v to alternator field terminal and watch battery voltage: does it change or stay the same?

 

[Big_John]

Just because the alternator and regulator are new doesn't mean they are good.

Here's the way the FSM does an alternator/regulator check. This assumes the battery is good and honestly, checking that battery would be first on my list before doing this test.

Take a voltage reading at the battery just for reference, car not running.

Disconnect the green wire from the alternator and make a jumper wire that goes from the connector on the alternator to the output post on the alternator.

Turn on the headlights on high beam and start the car.

Check the voltage at the battery again. It should be 14-15 volts at minimum. If it's not, there's a problem with the alternator. If there is, the problem is either the voltage regulator or the wiring to the VR.

Don't run the car for long like this. Just long enough to check voltage.

This duplicates the FSM procedure except you are using the headlights to load the battery rather than the carbon pile. What we are doing is bypassing the VR to perform the test. The VR controls the alternator by completing the circuit in the field to positive 12 volts.

 

[SPF Required]

Took the battery to AZ and they said it checked out great. Good volts and charge and now bad cells.

The guy there said a quick check way to see if the alternator is bad is to start the car, the pull the negative wire off the post of the battery. According to him, if the alternator is bad, the car would die instantly.

Wanted to float this testing idea out to you guys before I rely on the word of an autozone cashier and screw something up.

Whatdoyathink?

 

[mrfury68]

I think you do what Big_John explained in the previous post. It duplicates the factory service manual procedure and is not difficult to do.

 

[SPF Required]

Will do. I’ll keep you posted.

 

[Big_John]

Took the battery to AZ and they said it checked out great. Good volts and charge and now bad cells.

The guy there said a quick check way to see if the alternator is bad is to start the car, the pull the negative wire off the post of the battery. According to him, if the alternator is bad, the car would die instantly.

Wanted to float this testing idea out to you guys before I rely on the word of an autozone cashier and screw something up.

Whatdoyathink?

That's really not a good idea and one that I would not suggest. It will probably fry that new electronic voltage regulator and let's say the alternator is still working enough to supply ignition voltage, it won't stop running anyway.

The theory is that once the engine started, the battery wasn't providing power and all the ignition voltage was provided by the charging system. Guys used to do that back in the day of generators and mechanical voltage regulators, but even then, I don't know as it really was a good way to test.

BTW, you NEVER want to do that on anything with a computer in it (read newer cars) as it can fry the electronics and cost $$$$$$$$$$$ to fix.

 

[CBODY67]

As soon as the battery negative cable is unhooked, taking the battery out of the circuit, all of the voltage of the alternator will seek a ground elsewhere, in order to complete the trip between + and -. Where the voltage will try to seek ground, will be the easiest place it can do it, no matter what. Plus, the alternator output could spike to "max" in the process . . . not good for any electrical device which might be connected and operating.

In prior times, some of those "shadetree diagnostics" might have worked or not have caused many problems (as there were markedly-less electronics that there are now), BUT we never heard of the damage those things caused. Just that they did not work as somebody claimed they would. End of that "advisor's" "expert status", usually.

Although we can make electricity do many great things, it will ALWAYS get to the ground point that is easiest for it to get to if left to its own devices.

CBODY67

 

[Mr C]

I had a similar situation years back...turned out to be a broken wire that plugged into the field connector. Patched that and I was good to go thereafter.

 

[SPF Required]

Thanks for all the advice guys. I’ll get back at it in the morning!