# Twitchy voltage



## LouCabra (Jul 20, 2015)

I've had my 68 for about six months now. Chased down lots of electrical issues and thought I had everything nailed down. The other day I drove to town. When I came out of a store a few minutes later my motor wouldn't turn over, just clicked. Jumped it off and came to life. Drove it home. With the motor running I checked the voltage at the battery: 12 volts. 

After checking this forum I went through all the steps that were recommended and decided it must be the alternator. Picked up a new one and installed it along with an aftermarket temp/volt/oil pressure gage cluster (I have idiot lights). Got everything installed and jumped it off again (battery still drained from the last drive) and it fired right up. The really cool thing was all the dash lights finally came on bright and readable. I had written them off after replacing all the bulbs, circuit board and grounding the crap out of everything. The nev volt gage showed 14 volts. Life is good. 

The next day jumped in, cranked up, and looked at the gage again. This time the volt gage was twitching. Looked like it was bouncing between 12 and 15 volts. Not slowly rising and falling, but literally twitching. When the sun went down and I turned the lights on and all the dash lights were flickering with the twitching. Never going off but going dim to bright, rapidly. I put my digital multimeter across the batter and also the alternator. The meter was fluctuation between 13 v and as high as 15 volts. Since the meter has a digital readout the numbers were constantly changing because the lcd couldn't keep up with the twitchy voltage output. 

Has anyone seen this before? I though it might be the voltage regulator, but the twitchy voltage at the post on the lternator makes me think the new alt is bad. Any thoughts?


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## 05GTO (Oct 6, 2004)

New alternators should have a built in voltage regulator, I would unplug the VR on the firewall and check the voltage again. If it is still bouncing I would replace the alternator and install without attaching the VR and measure the voltage again. May also be a bad internal voltage regulator in the alternator.


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## PontiacJim (Dec 29, 2012)

I may be mistaken, but internally regulated alternators did not appear until the early 70's. The '68 alt should be externally regulated if its the original.

You can have the alternator tested or the VR tested. You may still have a bad ground/loose connection. But, the flickering sounds like the VR. You want to make sure you get the correct one for a Pontiac application and not one for a Chevy pickup because it will fit. 

Here is a blog I found that may be of some help if you read through it. I am not an expert on electric advise. I can usually sort through it by testing and isolating the problem -which can be time consuming to say the least. Gotta remember, a lot of the replacement parts offered through your local store are not original factory replacement parts and are probably more generic in application than actually fitting your car as needed. The original alternators also had lower amps and often people will begin to add bigger stereos, electric fans, and other power options that draw more than the factory alt puts out, so you want to take this into consideration on alt choice.

Check this out Internal or external regulator? - Chevelle Tech

:thumbsup:


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## pjw1967 (Mar 10, 2014)

Hi, Lou. I had twitchy voltage. This video is short but if you look at the firewall and not the light you can see it. https://www.youtube.com/watch?v=0ijp8l4siE4
As PJ said above the alt should be an external regulator. I put on a new reg when I got the last alt. Brand new Made In USA Duralast. After futzing with the flickering for awhile, just disconnected the reg. Bingo. Flickering stopped. Ordered a brand new Made In China solid state reg from Ames. No problems since. So......pull the connector to the reg and see what happens. Good luck.


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## 05GTO (Oct 6, 2004)

If your alternator is indeed a newer internally regulated alternator you can use *this adapter *to make it work with your external voltage regulator. I have this setup on both my 66 and 67.


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## LouCabra (Jul 20, 2015)

I don't think it is an internally regulated alternator. It has the same connections as the old one. A heavy gage wire that goes down towards the starter and two wires in a "connector clip" that plugs into the back of the alternator. Also was the only alternator in the auto parts store that said it was compatible with a 68 GTO.

I cranked up the car and sure enough the voltage was twitching. I unplugged the 2-wire connector (that I assume goes to the regulator) and checked the gage - no twitching, but the gage was reading around 16 volts. I probed the back of the alternator with my multimeter and it read 17 volts. I plugged the 2-wires back into the back of the alternator. Interestingly, when I unplugged the clip it seemed like my motor speed increased slightly and decreased when I plugged the wires back in. Checked the voltage again and found that the twitching seemed to stop, but the alternator was putting out 17 volts.

Took the voltage regulator out (mounted to the firewall) to look it over. Its a "Sorrensen" and from the looks of the inside and connectors it could be as old as the car. Cleaned the connectors and put everything back together. No more twitching, but the alternator is still putting out around 17 volts.

Am I correct in believing the voltage regulator is faulty? If so I'll order one from Ames. Is there any danger in running the car if it continues to put out 17-volts (until the new regulator comes in)?

Thanks everyone for the help!atriot:


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## 05GTO (Oct 6, 2004)

LouCabra said:


> Am I correct in believing the voltage regulator is faulty? If so I'll order one from Ames. Is there any danger in running the car if it continues to put out 17-volts (until the new regulator comes in)?
> 
> Thanks everyone for the help!atriot:


I would agree the voltage regulator is possible bad, overcharging isn't good for a battery, I had one explode on me a few years ago after leaving it on a charger overnight.


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## pjw1967 (Mar 10, 2014)

05GTO said:


> I would agree the voltage regulator is possible bad, overcharging isn't good for a battery, I had one explode on me a few years ago after leaving it on a charger overnight.


My understanding as well. You can "cook" a battery by overcharging.


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## pjw1967 (Mar 10, 2014)

" I unplugged the 2-wire connector (that I assume goes to the regulator) and checked the gage - no twitching......Took the voltage regulator out (mounted to the firewall) to look it over. Its a "Sorensen" and from the looks of the inside and connectors it could be as old as the car."

Lou, heads up. I'm getting above my pay grade here. I googled Sorensen Voltage Regulator. That's not a stock item. Stock is a 4 pin connector. Here's a link to the stock style one that Ames sells. 

https://secure.amesperf.com/qilan/D...39B&order_number_e=Mzk2NTYxOA==
&web_access=Y

You might want to check the harness to see if anything was cut off, like the other 2 wires.


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## LouCabra (Jul 20, 2015)

Pjs, obviously way above my pay grade too. However, the 2-wire plug I disconnected was coming out of the alternator. The voltage regulator does have four wires. It's my understanding that two wires come from the alternator and the other two come from the idiot light. I also tried unpluging the regulator and the voltage acted the same as when I unplugged from the alternator.

Here's another strange thing. With every thing in place, I turn the ignition on to start the engine, the idiot light turns on. As soon as it starts the light goes off. With either the 2-wire unplugged at the alternator (v-reg plugged in) or the v-reg unplugged (2-wire plugged in) the idiot light doesn't turn on at all. I thought if there was a problem with the alternator or the regulator that the light shoul go on. I wish I understood these thing:banghead:

I'm going to order the regulator from Ames and see what happens. I wish it didn't take so long to get stuff from them. I may try to get a temporary fix from a local parts store. I say temporary because from what I've read in these forums most of the parts store regulators are junk.

Thanks again for all the advise guys, I'll let you know how it turns out:smile2:


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## 05GTO (Oct 6, 2004)

If I remember correctly I will attempt to explain the external voltage regulator wiring,

The 2 wires connected to the alternator from the VR are connected to the stator and the alternator field windings and the VR monitors the output voltage of the battery. When the charging voltage goes over 13.8 volts the stator voltage is reduced thus lowering the output voltage of the alternator. The same happens when the voltage is low the VR will attempt to increase the stator voltage to increase the output of the alternator.

One of the other wires is connected thru the switch and when the car is being started the voltage to the VR is interrupted causing a relay in the VR to de-energize causing the Gen light to activate. The other wire connects to the GEN light and is connected to the same relay inside of the VR. The gen light does not monitor the output of the alternator but instead monitors the vehicles battery voltage, a low output alternator (11 volts) will eventually only charge the car's battery to 11 volts which will de-energize the relay and send voltage to the Gen light.

Here is a thread started by BearGFR with more details on changing from an external VR to a alternator with an internal VR.


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## LouCabra (Jul 20, 2015)

Picked up a new voltage regulator at a local auto parts store, plunged it in, and fired up. I'm going to go out on a limb here and guess that its probably a bad thing if the regulator smokes.

The alternator started putting out a little over 13 volts at the battery at first. Then I got in and reved the engine a little and looked at the gage. Life is good. Got out of the car to look under the hood a saw what looked like smoke coming out around the VR. Hard to tell for sure since the radiator fane was blowing and it happened so fast. Immediately shut the car off. Both the new alternator and VR came with a life time warranty, so I figured I'd go for broke and see if smoke was really coming out the VR. Cranked the car up again only to find new issues:

1. At idle, the idiot light is on. Give it some gas and the light goes out.
2. When idling up something sounds like a growling cat. I can only hear it inside the car and it sounds like its under the dash somewhere. Could be the VR bolted to the firewall.
3. Voltage is back up to 16+

Does anyone know how many volts an alternator puts out without being regulated? Before got the new VR it was up to 17 volts. That seems really high. The other day when I was testing the alternator and pulled the 2-wire harness out of the back the alternator the car was running. Could that have damaged it somehow and make it put out high voltage?

So frustratimg:banghead:


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## pjw1967 (Mar 10, 2014)

That sucks. Good question. What IS the "unregulated" voltage output. Let's hope some of our board colleagues can help you past this. Me, I stalled at new VR.


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## allpawl66 (May 9, 2008)

I have solid sate electronic US brand external regulators if in need , have sold dozens with all good results , send pm with email for details if in need . $35.00 shipped will accept original style Delco cover as well .


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## LouCabra (Jul 20, 2015)

Latest developments:
1. brand new alternator
2. brand new voltage reg (solid state still on order from Ames)
3. brand new battery
4. checked continuity of harness wires

Started motor. The twitching of the volt gage and flickering of dash lights looks to be gone. However, At idle, the generator light is on, volt gage reads approximately 17 volts, slight buzzing heard from dash area (volt reg felt like it is vibrating). If I rev the engine, even just a little, the gen light goes out and the volt gage drops to 14 volts. Does that make sense? Engine turns slow and the voltage output is high - Engine turns fast and the voltage output is lower (belt is tight and not slipping).

Any more clues?


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## pjw1967 (Mar 10, 2014)

I know this may sound weak, but have you tried a diff volt meter? If I read 05GTO's response correctly, the system is behaving in the right way. It's just the numbers that seem to be off. Or maybe I read it wrong.


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## LouCabra (Jul 20, 2015)

Good call PJW, that will be my next step. Will also try to pull the connectors out of the VR harness (the one with 4 wires) and make sure they are making a good connection to the VR. When I first got my 68 I was having problems with the tail lights. No matter what I did, new grounds, switch, bulbs, nothing would make the tail lights come on when I turned the headlights on. Finally fiddled with the harness that plugged into the headlight switch and viola! Tail lights. I've tested all the wires in going to the VR, but haven't checked to make sure they are making a good, solid connection.

Thanks for sticking with me!


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## pjw1967 (Mar 10, 2014)

I had trouble with my horn. Turns out that after 45+ years the connector to the relay on the firewall had tarnished badly. Got one of the wife's wooden nail files and used scissors to make a point on one end. Used that to get into the connector and the relay to brighten up the contacts. OK after that. Standing by for reports.....


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## LouCabra (Jul 20, 2015)

Its possessed:reddevil:

Disconnected the battery, pulled the little brass (copper?) connectors out of the alternator pigtail (one at a time so they wouldn't get crossed). Sanded them to bright, rubbed a little dielectric grease on them and plugged them back in. Used a multi meter to check continuity between the pigtail and the correct positions on the regulator and everything checked out ok. I haven't gone to town to get another under-dash voltmeter yet, but I did change the location where it was getting the positive feed. I had it connected to the + of the internal tach. cut that lead and tied into radio +. THATS ALL I DID!!!

Connected the battery back up so I could test it out again, but before I got in the car the "Gen" light was on. KEY WAS IN MY POCKET!!!

Started up anyway and everything seemed to be working OK. Gen light went off as soon as it started, volts at the gage was around 14, multimeter at the battery read 14.51, multimeter at the alt read 14.51. Turned the car off and pulled out the key and the Gen light stayed on:banghead::banghead::banghead:

So now I'm thinking it could be the ignition switch. What else could it be??? How in the world could the idiot light be getting power without the key in the on position??

Update: Its now an hour later. Went back and fiddled with the wiring again. Pulled the neg to the battery, unplugged the 2-wire pigtail off the alt, reconnected the battery - Idiot light (and that name is certainly true at this point) is on (no key in the ignition). Pulled the battery again reconnected the 2-wire pigtail, disconnected the 4-wire harness at the VR, connected the battery and low and behold - no idiot light. So now I'm thinking it must the new-new VR. Put the old, original VR back on. No idiot light. Started the car and I was back to twitchy voltage on the gage and flickering interior lights (including the dash lights, but not the Gen light). So now I'm back to faulty voltage regulators. Hopefully the solid state VR form Ames will show up someday and the world will be right again. I am still clueless as to how the new-new VR could be sending power to the Gen light without the key in the ignition. Maybe it is still related to the ignition switch. Maybe if I change a windshield wiper blade everything will work. So clueless!


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## Rukee (Feb 8, 2007)

Alt from Autozone??


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## LouCabra (Jul 20, 2015)

O'reilly's Auto Parts. I avoided Autozone after reading some other posts on charging systems. Unfortunately, I think everything made today is crap, regardless of where you get it.


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## Rukee (Feb 8, 2007)

I use NAPA only. Sure O'reillys and autozone might have cheap parts, but they have cheap parts. I had a guy bring me an alt from autozone and we went though three of them before he got a good one.


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## pjw1967 (Mar 10, 2014)

Hey, Lou. Happy New Year. Is it? Any progress? Inquiring minds want to know!


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## LouCabra (Jul 20, 2015)

Sorry for the delay. I received the solid state voltage regulator from Ames on Tuesday, but bad weather and lack of time have prevented me from getting to it. It's the first thing on the list to do this morning. Wish me luck!


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## pjw1967 (Mar 10, 2014)

You mean weather and life got in the way? Standing by.....good luck.


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## LouCabra (Jul 20, 2015)

*S U C C E S S ! * :bannana:arty:

Plugged in the solid state voltage regulator from Ames and got a steady 14.4 volt output at idle and no weird generator light issues. Still raining here so I couldn't do a road test, but I idled up to thermostat temp and tried lights on/off, heater fan, radio, and combinations of each. Stayed right right at 14.4. No more twitching needle or flicker lights.

Thanks to everyone for their advice and support thought this challenge. Hopefully, I'll have nothing else to report on this issue. For those reading this thread in the future, make sure you don't purchase any parts from discount or neighborhood auto part stores. I went through two alternators and three voltage regulators from local sources (none of which solved the problem), before I went with Ames. I never got anything parts from NAPA, but Rukee says they are OK. My advice is to go straight to Ames for your parts.


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## pjw1967 (Mar 10, 2014)

Excellent! Check the little tang on the reg that holds wire connector. Mine didn't grip tightly and I was afraid it might loosen up from vibration. So I trimmed it a bit to be able to push the connector all the way on.


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## LouCabra (Jul 20, 2015)

Thanks PJW. I ran into that and fiddled with it awhile. As a result the connector fits much better on the new SS reg than (all) the other VRs I went through. I was worried about how good the connection would be because I was never able to get the little brass connectors out of the plastic harness to brighten them up. Usually a tiny screwdriver stuck into open end of the plastic connector will free the wire and brass to slide out. However, I couldn't get any of the connections on the VR harness to come free. Anyway, I guess since it fit so far up on the spades of the VR, it made a good connection

Does anyone know what those female brass pieces are that fit into the plastic connector covers? For that matter, what are the plastic pieces that the brass fits into called? There must be some technical names for those things.


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