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Last cruise out 66/427, I discovered a buzzing like noise from under the hood. Upon further investigation I noted that the voltage regulator was the culprit. Did some research on the issue and found mine has points system. (So does my ignition system). So I cleaned up the tri-set of points, and so far it’s been quiet. It has a good ground so I don’t believe that’s the problem. I placed an external multimeter at the battery cables and am getting 14.5v. On its way out? Replacements units no longer have the old style contact points.
Many of the forum members have switched over to an electronic VR. They slightly modify it so you can use your original cover. Yours looks new. I would just keep an eye on it. Jerry
Is this a driver car or does it need to stay all original for judging? If a driver, I would put the 10D alternator in storage and replace with a 67 amp 10SI from a 70’s Suburban. You can get a plug-n-play harness from several vendors including American Autowire that don’t require any permanent mods to the wiring. The 10SI alternators work fabulously in my experience.
Last cruise out 66/427, I discovered a buzzing like noise from under the hood. Upon further investigation I noted that the voltage regulator was the culprit. Did some research on the issue and found mine has points system. (So does my ignition system). So I cleaned up the tri-set of points, and so far it’s been quiet. It has a good ground so I don’t believe that’s the problem. I placed an external multimeter at the battery cables and am getting 14.5v. On its way out? Replacements units no longer have the old style contact points.
Sounds good to go to me – the output voltage is good, the contacts are now refreshed – I wouldn't change it out.
Mike C. Thanks for that good info and link Car is not a driver. I had the numbers alternator rebuilt last year and am trying to get the car to NCRS 1st flight. Rather than replacing parts, I’ll just keep an eye on it.
Last cruise out 66/427, I discovered a buzzing like noise from under the hood. Upon further investigation I noted that the voltage regulator was the culprit.
Vibrating points type regulators, also called electromechanical regulators buzz. Normally you don't hear it unless a mounting screw or cover screw is not tight. These regulators work somewhat like a door buzzer in that a contact makes and breaks a circuit or circuits many times a second. They are slower when charging a depleted battery and quicker fully charged. The moving contacts are buzzing between resistor poles mounted behind the regulator rapidly switching them in and out of the field circuit.
If you measure 13.8 - 14.2 volts DC across your battery with the engine at a fast idle, with headlamps on, your regulator is fine.
If you measure 13.8 - 14.2 volts DC across your battery with the engine at a fast idle, with headlamps on, your regulator is fine.
Dan
Dan, Great explanation! Yes to the last part of the quote. I’m getting those measurements. Now if those readings are not achieved it’s obvious to replace the vr?
Dan, Great explanation! Yes to the last part of the quote. I’m getting those measurements. Now if those readings are not achieved it’s obvious to replace the vr?
Without those readings its obvious diagnosis is required. You can bypass the regulator and command full output with a jumper between the F terminal on the alternator and the alternator output stud (which is 12 volts from the battery). Engine running at high idle make this temporary connection with your meter across the battery. You should see between 16-18 volts DC. This is the alternator running at full unregulated capacity. No or low readings indicate a faulty alternator. Correct readings indicate a faulty regulator.
Now if those readings are not achieved it’s obvious to replace the vr?
Regulators like yours are easily adjusted if otherwise functioning properly. There is a screw to adjust the tension on the coil spring. Turn clockwise to increase voltage output and vice versa. You can do this with the engine running and voltmeter connected to horn relay and ground. The final reading should be done with the cover in place and at operating temperature. I like to disconnect the battery when removing or replacing the cover to avoid shorting contacts. There are other adjustments if you really want to get technical, but this is really easy.
Regulators like yours are easily adjusted if otherwise functioning properly. There is a screw to adjust the tension on the coil spring. Turn clockwise to increase voltage output and vice versa. You can do this with the engine running and voltmeter connected to horn relay and ground. The final reading should be done with the cover in place and at operating temperature. I like to disconnect the battery when removing or replacing the cover to avoid shorting contacts. There are other adjustments if you really want to get technical, but this is really easy.
I advise highly against this. His regulator and most in current service are reproductions and approximations of the original Delco design. The original Delco design is adjustable if done via shop manual instructions. These modern day replacements are not adjustable. Bending the armature or spring hook will ruin it. Regulators don't fall out of adjustment. Their contact surfaces pit, oxidize, create high resistance and eventually an open circuit.
Dan, When performing jumper wire test from F terminal to the 12v on the alternator, is there a possibility of damaging bulbs or fuses?
Survivor, I see no adjustment screw on this.
Dan, When performing jumper wire test from F terminal to the 12v on the alternator, is there a possibility of damaging bulbs or fuses?
Survivor, I see no adjustment screw on this.
Turn off the radio. But otherwise no. For the several seconds you have it jumped everything will be fine.
Ignore advice to adjust.
Dan
Last edited by dplotkin; Apr 17, 2024 at 11:52 AM.
I do not know about the electronic regulators for GM but there is an issue with apparently all of the electronic regulators made for pre-70 Mopar cars. I have a collection of them in the garage and every one of them puts out over 15 volts, most well over 15 volts. And unlike point type regulators they do not have a normal reduction in voltage output as they heat up. From what I can gather from the rest of the Mopar community, no one can find a reproduction electronic VR that puts out less than 15 volts. One re-seller of old stock and newer stock parts thought he had some but when I asked him to check the calibration of his equipment he was testing them on, he found it was off. All pre-70 Mopar electronic VRs appear to come from one or two common sources.
I don’t want 15.5 volts cursing through my old cars wiring systems, some of which are still original and in good shape. Some have disagreed that 15 volts on your harness is a problem but I’m not convinced, especially as old Mopars are known for some electrical issues. I converted my 2 old Mopars back to points VRs and adjusted them to operate from 13.8 to 14.2 volts.
I don’t know if GM electronic VRs have the same problem or not. I believe the VR on my 66 is an older electronic unit - I put it on there so long ago I have no idea of the source. It did measure down in the lower 14 volt range when I tested it so I’ve left it alone. I only bring this up to recommend if you install an electronic one, to test it out after installing and make sure it’s not over-charging. A lot of this reproduction and electronic stuff is Chinese crap.
Dan, as you know I own several Chrysler products and I have experienced the same problem with the electronic regulators enclosed in the original appearance Black Box. I found the same thing they all over charge. Thankfully as you point out a mechanical version is still available and I bought two of them to keep on the Shelf.
In my experience the electronic Regulators sold for GM cars with the 10 DN alternator charge fine. I have one of those in a 63 Impala and it runs at 14.2 volts on the nose.
I advise highly against this. His regulator and most in current service are reproductions and approximations of the original Delco design. The original Delco design is adjustable if done via shop manual instructions. These modern day replacements are not adjustable. Bending the armature or spring hook will ruin it. Regulators don't fall out of adjustment. Their contact surfaces pit, oxidize, create high resistance and eventually an open circuit.
Dan
My apologies for the adjusting advice. I made a bad assumption this was an OEM regulator with the adjustment screw. Thanks Dan for pointing this out.
Voltage Regulator
