Ok, so had the cap blow off the battery the other day, checked voltage at battery with truck running got 18.5 volts. No brainer, voltage regulator bad. New voltage regulator, now 18.1 volts at battery. Check ground on alt case and it's good but added ground wire from alt case to neg battery terminal anyway, still 18.1 volts. How is this possible, even if alt went bad, how will voltage regulator allow higher charging rate? I'm stumped. Truck is 65 econoline 170 six, voltage regulator is vr166 electronic, not points type.
Your new regulator may be out of whack, find a shop that rebuilds alternators and such, and have them test it and adjust it... Or find the instructions for adjustment, and give it a try, it isn't brain surgery...you just need to take it slow...
Believe it or not I have seen a battery cause an alternator overcharge. It must have something with the internal resistance in the battery causing the regulator ramp up .The battery load tested fine. Try putting in a different battery and retest the system....What have you got to lose?
This is always a good thing to do, rule out the battery early-on when diagnosing a problem. I usually have one around that I can charge and have swapped them out of another car as well. But don't drive it around if it continues to over charge, then you'll have 2 cooked batteries and the possibility of it blowing up in your face. Bob
High resistance in the circut where the regulator "sees" battery voltage can cause it to over-charge. I'm not familiar with Ford charging systems but a good service manual will tell you where to check and what the voltage readings should be.
Sensing wire may be too small (gauge) or too long, or poorly connected.... dropping voltage......... and fooling the alternator into outputting too much.
Does a Ford regulator have to be well grounded the way GM does?? Or, is it grounded and not supposed to be??
The new regulator could be bad, the last Ford electronic one that I bought was defective and overcharged the system. That being said it would still be a good idea to swap batteries and check the voltage to the sensing terminal. As you have had two regulators do the same thing.
That ford regulator senses battery voltage on the "A" wire, to ground. Check the regulator ground first. Fire the engine, read the charge voltage - the use a jumper wire from the regulator case to battery ground. If the voltage falls back to 14v, then you have found the problem. The "A" wire could have some bad connections causing the same issue. If the grounding was not the cause, probe the "A" wire with the system running & charging. If it is not within .2v of the charge voltage at the battery, there is the issue. B.
The voltage regulator is actually a sensor. The battery is the true regulator of the system. As has been mentioned, a defective battery or faulty wiring can cause the sensor/regulator to misunderstand what to tell the alternator/generator.
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