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Discussion Starter · #1 ·
My car wouldn't start the other day, so I put a charger on the battery and brought it up to 12 volts. I had inadvertently left my security solenoid on in the car and killed the battery.

I thought all was well until this morning when it wouldn't start again after driving it for about a half hour to 45 minutes. I jumped the car by pushing it and then put a meter on the alt (pos) and the neg side of battery. It read 10 volts, but was still hooked to the battery and it also was at 10 volts.

Later after another drive, I did it again and it said 6 volts and that is what the battery was at also. I took the alt to O'Reilly's to have it tested and the guy said he was having problems with the machine, but he'd try it and if it didn't work bring the car by so he could test it on the car. It tested out OK on the machine inside the store. Just for kicks, I bought a new alternator. Put it on my car and got the same results, so I returned the alt. and drove the car to them.

The guy came out with a tester that was for testing the alt. on the car, and once hooked up, it read "PLEASE USE ON 12 OR 24 VOLTS SYSTEMS." He said he had never seen that message before, but I didn't have confidence that he really knew what he was doing. He called someone else and he was stumped too and he was the assistant manager.

I'm charging the battery again so it will start on it's own, but I need to figure out what I might be doing wrong if anything. If I remember correctly, it should be 14+ at the hot side of the alt. What am I missing?
 

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You may have dropped a plate or cell in the battery itself.

You need to check the battery under load.

You need to see whats drawing the battery down?
 

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maybe time for a new battery. :anim_25:
 

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Discussion Starter · #5 ·
I don't understand, the battery takes a charge but runs down if I drive the car. It appears that the alt. is not doing it's job. If the battery is bad, does it cause the problems mentioned above with the alt. not putting out 14+ volts?
 

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I don't understand, the battery takes a charge but runs down if I drive the car. It appears that the alt. is not doing it's job. If the battery is bad, does it cause the problems mentioned above with the alt. not putting out 14+ volts?
To answer this question in the simple the answeer is No. However it is possible for a bad battery to kill the voltage regulator. Furthermore, if you kill a lead acid battery to many times or draw it down to far too many times it kills the batteries ability to recover. couple this with a defective alternator or alternator wiring, and you have the results that you are having. Check all the wiring to the alternator and the make suer it is all working as it should. then run the car and check the B+ on the alternator, also make sure that you have excited the regulator by reving the engin 1 or 2 time to 3500 rpm. if you have no charging 14.4 min at idle then you have a bad alternator..
 

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Did you or O'Reilly test the alternator with the battery disconnected?
And the new alternator also didn't put out 14V?
Or was each test done differently, including O'Reilly's malfunctioning tester?
Not sure if each time you tested either the battery or the alt, or tested both each time. Could be both are bad?
 

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Discussion Starter · #8 ·
I tried this and with battery at 100% I turned on the lights and the needle never moved off 12 volts even with raising the idle.

I'll disconnect the battery and see what that does.


 

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Just curious,did you recharge the battery with a
2 amp "trickle" charge,or a 10 amp charge?

I find a 2 amp "trickle" charge works best with an
automatic battery charger to top up a battery.
 

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You start with new battery. You test all with volt meter while running. Now you find there is no problem. You be happy.
 

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I tried this and with battery at 100% I turned on the lights and the needle never moved off 12 volts even with raising the idle.

I'll disconnect the battery and see what that does.
That test is for a external regulated alternator.
Is the new alternator a internal or external regulated alternator? Is the belt tight enough? A slipping belt with a discharged battery may not put out enoung voltage to ever charge the battery.
 

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Discussion Starter · #12 ·
Don, it's externally regulated and that's why I'm stuck. I was pretty sure it had nothing to do with the battery, but I don't know if it's the alternator or the regulator that gave up the ghost.

The last thing I tried was to start the car off the battery and then pull the positive cable. The engine died immediately, so I would say that takes the battery out of the equation.

Just before I did that I used jumper cables and a different battery with mine disconnected and got the same results.
 
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Check ground paths, negative side. Battery neg term to engine, engine to firewall, and, then, to regulator on fender well, if that is where it is located.

A separate test of ground would be to use a jumper wire with alligator clips on each end, regulator ground term on side to either engine, carb stud is OK< or, battery neg, check output at 2,000 rpms or so, best would be 14.20 volts, good is 13.80 volts.

Remote regulator ground is critical.

For the remote regulated alternator applications, there is a fully electronic regulator, instead of the stocker, Auto Zone caries them, Wells VR715, direct replacement, can also use stock Delco-Remy cover.

The VR715 basically switches the operation of the alternator, from turning the alternator on, then off, then on, then off to charge and regulate, to the same operation as an internally regulated alternator uses. The VR, and internally regulated alternator operation differs, in that the regulator "catches" (turns on) about 1,250 rpms, (cold, on choke, hot first start rev), then, actuates the alternator, holding it operational, not cycling it on and off. The excess over volt charge is then routed (dumped) back to ground, to regulate it. Alternator life and operation is greatly extended, this makes the remote regulator alternators function exactly like the internally regulated SI alternators.

I just looked on O'Reilly's Auto Parts website, and found this info,

Master Pro regulator, 2VR4, $21.95
"Detailed Description, Direct replacement for Alternator Voltage Regulators, upgraded to Solid State in many instances."

At this point, I'd remove the cover from the regulator, and try to manually actuate the point sets with the engine running, voltmeter across the battery, and see if the volts change. I know you have already checked the battery, and, the wiring from battery to regulator, regulator to alternator, and, the alternator, so, this would be the next step in the process.
 

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Discussion Starter · #14 · (Edited)
I had to drill out some rivets and found out this is a solid state regulator. Is there any way to check to see if it's good or not?

 

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Trifive Automotive Electrical Wiring Expert
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I tried this and with battery at 100% I turned on the lights and the needle never moved off 12 volts even with raising the idle.

I'll disconnect the battery and see what that does.
If the voltage did not increase during the above test with a external regulated alternator, the alternator is bad. It doesn't mean that the regulator is good, only that the alternator is not capable of producing enough voltage to be regulated. They could both be bad.
 

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Discussion Starter · #16 ·
So if the regulator is bad, would it also make a new alt. seem like it wasn't working at all? That might explain why the new alternator didn't cure my voltage problem.
 

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So if the regulator is bad, would it also make a new alt. seem like it wasn't working at all? That might explain why the new alternator didn't cure my voltage problem.
Short answer is yes. In my opinion if the reg is bad. Now is the time to upgrade to a 12si internally regulated unit. They will make more pawer and are pretty reliable.
 

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Discussion Starter · #18 ·
What happens to the wires if I change to a 12si unit. I don't want to mess with my harness.
 

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Trifive Automotive Electrical Wiring Expert
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So if the regulator is bad, would it also make a new alt. seem like it wasn't working at all? That might explain why the new alternator didn't cure my voltage problem.
The new alternator should still pass the full field test you did above. If it puts out more than 14 volts with the above test, then the regulator is bad also.


What happens to the wires if I change to a 12si unit. I don't want to mess with my harness.
You can jumper the wires at the regulator plug or splice them together, tape them up and leave them in the harness. Regulator terminals F to 4 and 2 to 3.
Here's a diagram.

 

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Discussion Starter · #20 ·
Thanks again Don. This is on my Corvette, so it may not be the same as a '55. I see there is a factory junction block in the diagram, but I don't see anything like that on my Vette.
 
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