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