Electrical system voltage fluctuating

[tbratz]

I have an issue with the electrical system that started on my 69' a while back. It seems that my voltage fluctuates constantly by several volts. If you watch the amp meter it bounces around and when I turn the lights on they flare. It seems that when this occured years back I replaced the voltage regulator and it cured the problem. I have replaced it this time and it still does it. I replaced the regulator with a factory motorcraft part, so it isn't some off brand. I have cleaned and tried all the gounds, connections at the regulator, even tried two different alternators and it still does it. When you put a volt meter to the system the voltage reading will actually jump up and down by several volts. It is really becoming annoying and not to mention embarrassing sitting behind someone at night as my lights flare at them! Any suggestions or ideas I would appreciate it.

 

[Broncobowsher]

Next time it acts up, take the volt meter and measure across;
Engine block (altenator case) to body
Body to negative on battery
Negative on battery to engine block (alternator)
If you get fluctuations of more then half a volt then there are poor grounds.
Also the regulator body to the battery ground.

Next trick, on the regulator, measure the voltage difference between the (hope my notes are right) "A" terminal and the positive battery post. IF I remember right the "A" post is the reference point for the regulator, if it drops then then alternator output goes up.

IF you get any of the above to go over a volt, you have a problem.

 

[jpalmer]

Do you have any high current electrical components (stereo amp, radiator fan, water pump, etc.) that could be surging or cycling due to a bad relay or sensor? Probably something you already looked into, but sometimes it can be something stupid that was overlooked.

 

[Viperwolf1]

I ran 2 gauge cable from the alternator case to the passenger side frame rail. From there another 2 gauge cable to a dedicated ground stud on the inner fender where the battery ground and other electronics grounds combine.

 

[tbratz]

Thanks for the quick replies. I am not running any other accessories, electrical system wise, everything is stock. I also tried running those exact grounds as suggested, but the symptom still occures. It seems to level out a bit at higher idle. I'll try metering those connection and see what happens.

 

[Viperwolf1]

Make sure the belt is good and tight too.

 

[DirtDonk]

Sounds like one of the main components still. Either the regulator (even though it's new) or the alternator itself.
Can you pull it off and have it tested by someone?
Anybody that you can swap regulators with just for testing?

Also, are the flucturations consistent? Or do they vary in frequency and intensity? Reason I ask is that if it varies then maybe there's a bad connection or wire that you missed in your search.
Oh, and top brand or not, it's more common than you might think to get a bad regulator right off the shelf. Could even have been someone else's return! You just never know.
How's your RR (return-relationship) with your parts store?

Just a couple of things to think about.
Good luck.

paul

 

[tbratz]

Thanks Paul, I know what you mean about the parts. I did try switching an alternator with a good one from my 74' F250 and I also tried the regulator and still does the same thing. It is pretty much steady as far as intensity goes. It does seem to level out a little at high RPMs though.

 

[DirtDonk]

Hmm, so this one's not going to be easy then, is it? Rats!
Have you done any work to it lately that might have effected anything? Been under the dash or hood fiddling with stuff in other words?

What general condition are the wires in? I'm just wondering if perhaps your main connection at the back of the ammeter is corroding and causing some erratic electrical flow issues. Not very common, but not impossible either.
Maybe even the main fusible link finally giving up the ghost?
How old are the main battery cables?

Sorry, I just re-read the first post and you already said that you'd tried another alternator. Missed that one.
Just the fact that changing the regulator fixed it the last time kind of makes it look like something in that area again though, so I'm trying to think of something you may have missed.
Stock original harness? Maybe the section between the alternator and the regulator is going bad under the wrap?

One last thing I have to mention. The early type of wire-run through the firewall behind the fuse block sometimes had some issues with corrosion at the connectors (well, they ALL had that!) and some wear-through in the insulation of some wires. This might be the time to bite the first bullet and, with the battery disconnected, closely inspect all your wires at the fuse bloc / floor junction. Maybe even un-screw it from the floor and take a look-see to see what's up behind there?
I'm not really sadistic and trying to make more work for you (really!) but I've seen a '69 and a '70 both with problems in that area. And the '69 was a complete melt-down, so it really is worth mentioning.

Paul

 

[70_Steve]

If you watch the amp meter it bounces around and when I turn the lights on they flare.

Not sure exactly what you mean when you say the lights "flare". A common issue with the charging system, combined with the complaint that the ammeter bounces around, is the headlights get brighter and dimmer at idle. Not so noticable at speed. One fix for this is to replace the stock style electro-mechanical voltage regulator with an all solid state one. A regulator from a 78 Granada comes to mind as a direct replacement.

I resolved this problem by upgrading the alternator to a 3G!!

 

[bronko69er]

Yep! Relace the stock regulator with a solid state (Napa # VR440SB), bout $15.
Problem solved.

 

[Louie]

Yep! Relace the stock regulator with a solid state (Napa # VR440SB), bout $15.
Problem solved.

I went solid state a while ago & it stopped my fluctuations.

 

[76SPORT]

I also had the same problem on my 76 bronco. I replaced the regulator and it still did not go away. Further inspection revealed that the voltage regulator plug was coroded and not making good contact with the regulator. NAPA has a replacement plug for $5.99 and after installing the problem went away. Also had the dreaded headlight flicker and I wired up a a pair of relays to the battery & headlights, and solved this issue as well.

 

[DonsBolt]

If none of the above advice works, you might want to go to a one wire alternator. and instal a voltage guage.

Hell it just might be a good time to do it now.

Get a hold of Ray and get one of his alternators. I did it last year and was one of the best mods I have done. It gets rid of the old style voltage regulators, as the new Alternator is internally regulated. You run one wire from the alternator, and get rid of all the wires to the voltage regulator.

Then just instal a volt meter and be done with old technology

 

[sprinksbeme]

Don't assume your battery is good. Batteries can cause all kinds of problems and still start your Bronco. Have someone load test it. Or just swap it out for a known good battery.
I always start at the battery for electrical problems. Alternator and regulator can not do anything but what the battery tells them it needs.

 

[tbratz]

Thanks for all the awesome information and things to try. I am going into town this week so I think I'll start with the Napa regulator, thanks for including the part number and it seems a cheap place to start. Looks like I'll have a lot of LEADS to follow. I have heard a lot of good about switching to the 3G alternator. I was going to convert over a while back but someone suggested that the old stock wires on my Bronco would not be able to handle the extra amps without causing more problems. But I see by the forums it seems to be a popular upgrade.

Thanks, Tony

 

[RRRAAAYYY2]

Couple of things. If you plugged the new regulator in before you bolted it to the fender, you likely blew the new regulator up.

Be nice to know if your voltage is going from 14 to 17volts, or from 14 to 12volts. The regulator you have has I A S F terminals on it. What kind of shape is the plug in?

The A terminal is responsible for telling the regulator what the voltage in the system is. If there is lots of resistance (broken/frayed wire) it could cause the alternator to over charge. Likewise if this connection is right broken it will stop the alternator from charging.

My thought is instead of replacing the regulator, maybe replace the wiring harness end, they are less than $10.

 

[tbratz]

The plug and all the wires look good. I did follow the wires out, no frays, cracks etc. The voltage goes from 14-12.