Erratic Voltage

[CFranks]

Hi all. Last few drives my voltage has been a very erratic. I'm used to it sticking at around 14.5 V fairly steadily once it is activated, but it has been jumping up to 16 and sometime even 18+V, and then suddenly dropping back down to less than 13 (which means it's stopped charging), then back up again. I also hear what sounds like whining coming from behind the dash/ engine bay when it jumps up. My assumption is i should throw the alternator into the bin but wanted to see if I could be missing something else. I have a 427W ford racing engine with a 1-wire alternator. Alternator is about 6 years old, although the car is newly titled late last season so only has about 700 miles on it.

I was planning on upgrading to 3G at some point so this could be my trigger, but just want to make sure i'm not missing something else that could drive this behavior?

[edwardb]

Sounds like maybe the regulator in the alternator let go. Your local parts store can test it. You won't get a lot of love from some forum members for 1-wire alternators. I've used them a couple times without any issues. But stuff breaks.

[rich grsc]

Man, you talking about me again.:rolleyes: Yep, my belief is tractor parts don't belong on these cars. Get you a nice small case 3G alternator, and never look back. https://www.dbelectrical.com/products/alternator-3-0-aerostar-92-93-94-7-5-f150-f250-f350-pickup-96-97.html

[edwardb]

Actually I wasn't thinking of anyone when I said that. Several have voiced similar opinions. But whatever. FWIW, the 1-wire alternators I've used were Tuff Stuff brand from Summit. They claim they produce voltage at low RPM which I found to be the case. https://www.lsxmag.com/tech-stories/ignition-electronics-efi/alternator-selection-one-three-wire/.

[swwebb]

Couldn't be something as simple as a loose belt. :confused:

[CFranks]

Couldn't be something as simple as a loose belt. :confused:

Thanks. One would hope, I did check while it was running and didn’t notice any hiccups but I’ll check the tension again. I’m also going to check my engine ground, that could also be a driver of this behavior. I’ll still probably replace the alternator as well since they’re fairly cheap but want to make sure that’s the culprit.

[CraigS]

I have had a one wire alt since 2007. Never have had a problem w/ it. Some times I notice right after startup that it isn't charging. A quick stab at the gas to get the engine over 1500 fixes that.

[CFranks]

Hi all, just to close this off, the primary issue appears to have been a poor engine ground. After cleaning up the ground situation the erratic nature appears to be gone. I still will probably replace the alternator shortly but seems good for now. Thanks to Mike Forte for the suggestion.

[FLPBFoot]

Thanks. One would hope, I did check while it was running and didn’t notice any hiccups but I’ll check the tension again. I’m also going to check my engine ground, that could also be a driver of this behavior. I’ll still probably replace the alternator as well since they’re fairly cheap but want to make sure that’s the culprit.

I too have a 1 wire Tough Stuff alternator. Working well so far. Did you install a ground wire from the alternator case to the engine? I have a Blue Print motor and they indicate you should not rely on the alternator mounting hardware to provide a solid ground. I ran a wire from the alternator case to the motor block where the oil dip stick mount bolts to the block.

Just a thought.

Steve