Voltage Regulator Digital vs Mechanical

[albert 5694]

Hello i have read most of the threads hear about voltage and how to test but i have not found the answer or i need it clearifyed for me a little better iam working on my 69 GTX with the 440 4 barrel with factory AC. The issue i am having is it is running at 15 volts at the battery pretty much all the time it tends to drop to 14.88 when i speed it up so i have tried 2 digital regulators and they both read the same and act the same so i went and got a mechanical one to try i installed it and the voltage dropped to 14.48 but after only about 1 to 2 minutes i noticed it starting to smoke and it keep getting worse so i shut it off right away and put one of the digital ones back on let it run for about 15 minutes no smoke the cover was cool and the voltage stayed at 15 volts all the time. I have a brand new battery with a static charge of 12.8 to 13.0 in the car less then a week old. I checked voltage with it running and at the battery it is 15.0 volts and at the output of the Alt i am getting 15.5 all the time so i turned the headlights on and the battery reads 14.88 and it still is 15.5 at the Alt. My question is do you think the alternator could be my problem and the voltage regulator cant drop the voltage to closer to normal. Any advice would be appreciated greatly, Hear are the 2 types of regulators i have on and tried the one on the left with the gray cap is the one that reads good voltage but smokes right away. Do you think i need to take my Alt in and have it tested?

 

[hunt2elk]

All the new 1969 and older style electronic regulators are putting out 15 - 15.2 volts. Higher than I like. Bothered me so much that I converted my cars over to the Denso alternators with internal regulation.

 

[lewtot184]

May want to check the regulator for a good ground.

 

[toolmanmike]

Hello i have read most of the threads hear about voltage and how to test but i have not found the answer or i need it clearifyed for me a little better iam working on my 69 GTX with the 440 4 barrel with factory AC. The issue i am having is it is running at 15 volts at the battery pretty much all the time it tends to drop to 14.88 when i speed it up so i have tried 2 digital regulators and they both read the same and act the same so i went and got a mechanical one to try i installed it and the voltage dropped to 14.48 but after only about 1 to 2 minutes i noticed it starting to smoke and it keep getting worse so i shut it off right away and put one of the digital ones back on let it run for about 15 minutes no smoke the cover was cool and the voltage stayed at 15 volts all the time. I have a brand new battery with a static charge of 12.8 to 13.0 in the car less then a week old. I checked voltage with it running and at the battery it is 15.0 volts and at the output of the Alt i am getting 15.5 all the time so i turned the headlights on and the battery reads 14.88 and it still is 15.5 at the Alt. My question is do you think the alternator could be my problem and the voltage regulator cant drop the voltage to closer to normal. Any advice would be appreciated greatly, Hear are the 2 types of regulators i have on and tried the one on the left with the gray cap is the one that reads good voltage but smokes right away. Do you think i need to take my Alt in and have it tested?

View attachment 1728633

View attachment 1728634

Dig around here and on FABO about overcharging. You may find you have other issues that a regulator won't fix.

 

[AR67GTX]

I’ve had new mechanical regulators smoke when fired up for the first time, but it died down after a couple of minutes and then was fine after that. It had the same type cover as the white one. The voltage can be adjusted in those if you think it is still too high. It doesn’t sound like you have an alternator problem. If you can turn on your lights, the radio, and fan on high and maintain at least 13 to 14 volts at 1000 rpm’s I don’t think anyone will find a problem with the alternator.

 

[451Mopar]

Troubleshooting steps (all measurements taken with engine running):
1 - disconnect the regulator output "FLD" wire that goes to the alternator. The alternator should not charge, and no voltage should be seen at the alternator field connection. This will make sure the harness has not been modified for a two field connection alternator like used on 1971 and up cars.
2 - Reconnect regulator output. Alternator should charge. Check the voltage at the regulator "IGN" positive probe and the regulator mounting tab negative probe. This should ideally be the same voltage as the alternator output voltage indicating the regulator is controlling the alternator output is the voltage sensed at the "IGN" input of the regulator.

If the voltages are the same, but the voltage is too high, the regulator is likely bad.

If the regulator "IGN" to case voltage is normal charging voltage, then either the regulator case / body ground is bad, or there is resistance in the "IGN" wiring that is not letting the regulator "sense" the correct alternator output voltage.

If measuring voltage from regulator case to battery negative terminal, it should be zero volts. A voltage reading here indicates bad grounding to the body / regulator case.

If the ground checks out good, jump a wire from the battery positive terminal to the "IGN" of the regulator to bypass bulkhead / switch / ammeter voltage drops from possible bad connections.

With the regulator case properly grounded to battery negative, and the regulator connected the battery positive, the regulator will adjust the FLD output current (or pulse width) to control the alternator output voltage to the regulators set voltage for the temperature.

 

[HALIFAXHOPS]

The FSM has the regulator outputs listed think it is 13.8-15.3 for most.

 

[68 Sport Satellite]

I had same issue. Solved it with adjustable electronic VR that has adjustment pot on back (eBay, rectangular pancake style). Should be set to 13.8-14.2V while running.
Someone mentioned that the VR you show in the photo is adjustable - I haven't heard of that and would like to know how those adjust.

Here's the one I installed and it works great. Bought a 2nd one as a spare and keep it in the trunk.
Transpo Heavy Duty Adjustable Voltage Regulator C8313 - for sale online | eBay

 

[AR67GTX]

The mechanical ones are adjustable internally by changing the spring pressure on the points.it takes very little adjustment to get some change so it’s usually takes a couple or more efforts to get it dialed in to where you want it. If I remember correctly lengthening the points between the spring (bending the lower anchor down) increases voltage and shortening lowers it. The general process is described in the FSM.

 

[Jonas Nordstrom]

After having gone through a couple of old style regulators I also changed to the 70s style adjustable (pot on back) regulator.
Works like a charm.

 

[451Mopar]

I had same issue. Solved it with adjustable electronic VR that has adjustment pot on back (eBay, rectangular pancake style). Should be set to 13.8-14.2V while running.
Someone mentioned that the VR you show in the photo is adjustable - I haven't heard of that and would like to know how those adjust.

Here's the one I installed and it works great. Bought a 2nd one as a spare and keep it in the trunk.
Transpo Heavy Duty Adjustable Voltage Regulator C8313 - for sale online | eBay

I agree, the Transpo C8313 works well on my car also.
EBay has regulator and connector pigtail for $21.09:
Transpo Heavy Duty Adjustable Voltage Regulator C8313 - for sale online | eBay

 

[albert 5694]

Thanks for all you advice i did some testing like 451 mopar sugested and found everything appears to be working. I put it all back together and now the voltage at the battery has dropped to 14.5 to 14.7 from 15.02 could this be from removing all the connections and re installing them made a difference by them being scraped from removing and re installing? The only thing i did notice was when i did the test for voltage at the output of the alternator 15.6 and then checked the voltage at the IGN. terminal on the regulator i was getting about 14.8 the ground checked ok the voltage was the same with an additional wire from Bat- right to the case there was no difference so grounding dose not appear to be an issue. If it stays at no more then 14.7 i can live with that for now and in the mean time i will keep digging and if not i may convert it to the adjustable 70s regulator as a last resort. I did noticed the mechanical voltage regulator ran around 14.4 but i am hesitent to use it because as i said earlyer it started smoking shortly after i let it run i dont know if this is normal and it will clear up or if there is something wrong with it. I know the digital one never gets hot and has better balance on the gauge when there is a draw. Please let me know what you think and i will keep everybody up dated on my succsess.

 

[AR67GTX]

The smoking is probably normal. Mine did it the first time. Mechanical regulators also have a pattern of putting out a bit higher voltage on a cold start but dropping down a little once warmed up. By a little I mean I’ve observed as much as 3-4/10ths volt.

 

[Sinitro]

Down side of mechanical regulator is wear/tear of its points, making break contacts multiple times. An electronic regulator the switching done by the power transistor..

 

[RJRENTON]

All the new 1969 and older style electronic regulators are putting out 15 - 15.2 volts. Higher than I like. Bothered me so much that I converted my cars over to the Denso alternators with internal regulation.

WHY do you not like the slightly higher 15.0 volts? Bear in mind that it's average voltage. What is the voltage at idle, in gear, with all accessories on? Likely it's lower....14.0 volts or lower. In the mechanical voltage regulator, the internal contacts switch between no internal resistance (full voltage applied to alternator's field and maximum output). When the system voltage increases, the internal contacts move to the mid position and the circuit is thru the 2 underneath resistors, reducing the alternators field voltage is reduced to approximately 6--8 volts and the alternators output is reduced to approximately 12 volts. IF the system voltage continues to rise, as in light loads or at highway speed, the voltage regulator's internal contacts move to the bottom contacts, turning OFF the alternators field voltage thereby turning off the alternators output. All of this action is controlled by the internal spring tension. This on/off action is continuous and the system voltage averages ~ 13.5 to 14.5 volts.
The electronic regulator functions similar but senses an INTERNAL VOLTAGE DIVIDER NETWORK, to sense changing conditions and controls an internal NPN transistor to switch the alternators field voltage to maintain a similar system voltage as the mechanical regulator. The internal voltage divider network determines the output voltage.
Why would you consider a Denso one wire alternator?....it uses an internal regulator that functions the same as the external electronic regulator. What is the determining factor??? What is your source of information?? Hopefully not some "buddy" who has no clue as to how and alternator is controlled or what the optimum system voltage is. A lead acid storage battery is a forgiving device, slightly higher charging voltage slows the sulfation process which may increase its life. IMO...do not install a Denso alternator but run what you have with the electronic voltage regulator.....
BOB RENTON