73' 351 Cleveland Charging 17v

Josh D

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Oct 16, 2016
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I restored this car back in 1997 and rewired the connectors to the voltage regulator because squirrels had chewed the plug off. Everything had been fine since then until last month I started having issues. I checked the voltage charge of my battery while the car was running with first a battery tester then a multi meter. It was fluctuating between 12v and 15v, so I checked the voltage regulator connectors and there was one frayed wire and some corrosion. I bought a new voltage regulator and a new plug, when I finished installing them the charge was no longer fluctuating but it was overcharging at 18v. I plugged up the original regulator and it was also overcharging at 18v. I read somewhere that the voltage regulator has to be grounded to the body so I bought new bolts and ran a ground wire off one of the bolts to the shock tower bolt to ground it. I cranked the car up and it is still overcharging at 17v, even after it idles down, or when I rev up the engine. I'm not sure if one of the plug wires for the regulator had to be ground or just the body, any help would be appreciated
 

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Your gonna fry that battery if you haven't already . If you think it's a ground problem, run a long jumper wire straight to the negative of battery. Can't get any better than that. If that works, got to find a better ground. What about the stock ground location? Is it clean paint free?


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I had to replace the original battery it got cooked, and that's when I realized I had a problem after I replaced the voltage regulator and the plug. I have tried to research the location for a ground on the voltage regulator but I cant find one. The only thing I can find out is that some of them ground to the firewall, was hoping someone could tell me how to properly ground out the regulator, if it is a wire or something else I may need to do. I'll try running a ground wire to the negative post from the body of the regulator. I'll also unplug the regulator and see if the battery is still overcharging because that may mean a wire may be grounding that shouldn't be or a problem with the alternator I think.
 
Have you checked each wire to the alternator/voltage reg plug. From what I was seeing is part of your ground is clean paint free surface behind bolt holes where regulator mounts. I would check each wire for continuity going from alternator to regulator plug. Is alternator/ regulator a match for your year? Bad new regulators are rare. But if all else checks out see if shop will warranty the new one you bought. Wouldn't it be something if parts store returned a shorted one for customer, and you ended up with it. Keep us posted what you find.


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So far ive tried running a ground directly from the negative post to the voltage regulator. Tried sanding the black paint off of the inner skirt to get better ground contact. Replaced the regulator pigtail plug wires, I even replaced the alternator and nothing has worked. The regulator that I have on there is brand new and I have the receipt still so I will try returning it tomorrow for another one. The battery reads 17v while the car is running( I only leave it running long enough to test it with the multi meter ) I have also used the multi meter to test the alternator by placing one lead on the batter connector on the back side of the alternator and one on the negative post of the battery. I get a 17.9v reading from the alternator when the voltage regulator is plugged up and a 12.5v when it is not plugged while running
 
The chances of having this many bad parts would be astronomical. I re read your first post, and noticed that rats ate through the wires. At this point, I would replace all the wires with new ones. It's possible maybe a field wire or ground wire could be touching. Somewhere you've got to be getting a short, that's causing this. I'll bet somewhere in the wiring loom, theirs an insulation that wore through by the rats eating it. Beyond that it's time to tow it to a Ford pro.


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