I own a 65 327/365 cpe. It has the correct 37amp alt installed. The car is only driven around once a month since it has started getting cold and rainy outside. I have to charge the battery when I decide to drive it. So I think that may be normal. It usually gets me where I going with no issues.
Last Friday I decide to drive it. Charged it for a few minutes and went to work. Cranked it up after I shut it off at work just to see if it would do it. AOK. When I got off work it was dead. Got a jump to go home. It was a cold day so I said maybe it was just cold. After 5 miles or so I downshifted into 3rd to pass granny. It stumbled as I got on the gas about 3500 rpms so I backed off and passed her. At the stop sign my car stalled again. It woud not crank. Got a jump (not from granny) and drove home without my lights or heater. He said he had been watching my tail light getting dimmer and dimmer.
I tested the alternator stud with the car running @ 2000 rpms after I fully charged the battery. It only showed battery voltage or less. about 11 to 12.2 volts.The meter deflects all the way near 35 in the negative and stays there with the fan on high and lights on. So the alternator is not kicking in.
The next day I go to Advanced Auto and buy a Sorenson regulator. A solid state one. Same results. I research this forum and find a slew of great info...thanks plaidside and others. With the key off I get voltage at the regulator plug at the red wire, Battery voltage. I also get 3.08 volts at the black/white wire. I check continuity between the wire and it goes to the "r" terminal on the alt. I disconect the plug and I get 3.08 volts comming out of the alternator. So a leaky diode. I take the alternator to the alternator shop where it was rebuilt a year ago. He said that even if it had a leaky diode it still should charge while the car was running. Oh, he put the alt on his machine and did the same test that I did at home by putting 12volts to the field terminal. It rose to 16-17volts. He told me that it was good. I said I knew it was good that I wanted him to change the diodes. He said again that it still should charge while running and that the alt was not my problem. He said put it all together and bring it by the shop and he would look at it. I don't know what he could do since he told me twice while I was there that he didn't have a multimeter.
Later today I took the alt to Advanced and they tested it with a more high tech and less dusty machine and they told me that it was o.k. too. I have changed the regulator, wires from letric limited are less than a year old, battery is less than 6 months old. All the grounds are clean and tight. Main battery cable goes to the starter bolt, another goes below the horn relay. They all are fine. The wiring harness doesn't even have a nick in it. I probly wasted my money and baught a ACDelco regulator for 55 dollars. It will be in tomorrow. I don't know what else to try. Hope and pray it will work tomorrow.
Any other ideas?

 

Your battery has expired, get a new one. That's the problem. Sitting for long periods of time and only giving a few minutes charge does no good.

 

My next step would be to swap in a known good battery( borrow the one from your wifes car for a few minutes, if possible) and see where you're at. That charging system doesn't sound like it stands a chance with your current battery in there. Steve

 

Even if I removed the battery it should still show a charge, shouldn't it?

 

I agree!! i put a new battery in mine and had problems like you have. the new battery i bought was no good.. NEW BATTERY!!!

 

Almost all parts stores can check the battery for free.

 

o.k. I will get the new regulator. charge the battery with a charger and drive it up there and have it checked out. Thanks for the advice

 

Nope. You must have voltage on the field of the alternator in order to get a charge. No battery - no field - no charge. Very weak battery - very weak field and not much charge (if any). Misconception that when the Amp gauge goes from hard charging to zero - your battery is fully charged. Not true. If you don't drive it fairly regular then the battery charger is your battery's best friend.

 

Why spend money on a regulator if the battery is n.g. ?

 

o.k. I got the battery installed. Had my son test the stud of the alterator and the positive post to the battery. 11.2 volts at both places while running at 2000 rpms with the lights and heater fan on. My ampmeter on the dash pulled way to the left and stayed there. The new battery is a titanium 700cca from advanced auto and was tested good before I took it out of the store. My old battery was bad. Before cranking up the car the battery had 12.5 volts. After running the car for 5 minutes to check the system it is down to 12.2.
The ground is good on the regulator and I have tried three of them. Any ideas now why the regulator isn't telling the alternator to kick in?

 

Hello

I had that problem as you described...Make sure your voltage regulator wires are in good shape...Connections are clean...Also check the connection to the firewall..Make sure it the connection is on thier TIGHT..Sometimes it can be hard to tell...I think you have a wiring problem...

Good luck
Pete

 

I wrote a paper on this subject. Everything you need to understand and check your system should be in the article.
Any other questions just ask.

http://temp.corvetteforum.net/classi..._Testing.shtml

 

Hello Plaidside,
I have studied the articles and I really appreciate the help. I do have 3.50 volts at the number 2 terminal of the regulator and when I unplug the connector from the alt I get 3.50 volts comming out of the stud on the back. I understand that it means I have a leaky diode. When they tested the alternator on the bench they sia at two different places that it was good. They even said that the diodes were good. Is it because they are not using a regulator with the machine? I believe you about the diodes. Could the testing machine at the store be geared for newer style and the diode reading they are giving me false? Last question, With a leaking diode, shouldn't it still charge while running or will that small voltage keep the regulator from working right? thanks!

 

Here is the alternator test procedure from the service manual.

p.s. The "Delcotron" is the alternator.



ALTERNATOR OUTPUT TEST
Voltmeter Method
1. Disconnect the two-terminal connector from the Delcotron "F" and "R" terminals.
2. Connect a jumper wire from the Delcotron "BAT" terminal to the Delcotron "F" terminal. This provides a full field excitation.
3. Connect a voltmeter from the Delcotron "BAT" terminal to the Delcotron "GRD" terminal.
4. Start engine and turn on high beam headlights and either the high speed on the heater blower or medium speed on the air conditioner blower motor. Slowly increase engine speed to 1500 rpm or slightly above with 6.2" generator run engine at 600 rpm and note voltage reading obtained. A voltage of 12.5 volts or more within a few minutes indicates Delcotron output is satisfactory. Stop engine and reconnect wiring.
CAUTION: When performing Step 4, engine speed should be increased slowly to prevent the unregulated voltage from exceeding 16 volts during test. If battery is in a normal state of charge, voltage will exceed 12.5 volts as soon as engine speed is increased.
5. If voltage is less than 12.5 volts, refer to the appropriate shop manual for Delcotron trouble diagnosis aids (Diodes, field circuit checks, etc.)

 

That was one of the first test I done. The voltage did climb. That was the first test the lt repairman did also. He said my alternator was fine. If one or two diodes are out will that cause my regulator not to work? Thanks

 

Run a jumper wire from the field post in the alternator {it`s in the plug location stamped 'F' on the case} to the battery post on the back. {the one with the red isolator} With the engine running this will full field the alt and it should charge if it`s any good..

This test works on all the makes.

Hell, "buns" has it right! Follow his lead it`s the same...

 

East test for diode problems, use your VOM to check resistance between hot terminal and alt case, then reverse leads, you should get zero or infinte resistance as they are switched. If you don't get infinite one way, change your diode plate. Bad diode or two can cut charging capability by 1/3 or 2/3. bad diodes will also drain your battery when car not running.

The VR may not work if it doesn't see a higher voltage from the alt than the battery has, but that is a quick SWAG on my part.

 

Vetarun,
If you have 3.5v at the #2 term of the regulator plug, with it disconnected, then you have a leaky diode.
Try this:
Unplug the regulator
Connect a voltmeter to the #2 wire of the regulator plug & ground
Start engine
Use a jumper, a cotter pin works great, between the batt (#3) and F term of the regulator plug.
You should get at least 8 volts at the #2 term
If not, change the alternator.
Explanation:
When you start the engine a small amount of current is sent from the dash, or idiot light if equipped, to the # 4 term of the regulator. It then goes out the ‘F’ term of the regulator to the ‘F’ term of the alternator to excite the field to start the charging cycle. Once this occurred, it will charge with the battery disconnected.
I DO NOT RECOMMEND THIS TEST! It only tells you that the alternator is putting out enough of current for the ignition circuit.
Now once the cycle has started, a small amount of current is sent back through the ‘R’ term of the alternator to the #2 term of the regulator. This current closes a set of points in the regulator. Now two things happen.
Current from the #3., (battery wire), will be used to power the field circuit for charging.
Also batt voltage is sent back out the #4 terminal to the dash to turn the idiot light off if so equipped.
So your alternator could test OK on a test bench, but it could still not operate on the car.
Sorry for the long winded explanation.
Joe

 

Is the tab that's 90 degrees away from the other four on the regulator the ground connection? The aim shows it screwed into the case. Other post says it should go under the bolt that secures the regulator.

 

I believe the terminal you are referring to is where the radio capacitor connects to. The other end of the capacitor is connected to on of the mounting screws.