Kevin88RRC
Well-known member
Alt readings are at the battery post on back of alt and ground strap to block.With the engine idling and the light is out, the alternator is producing > 12V.
Where and how are you specifically taking the voltage readings?
This is puzzling.
How much larger than OEM is the alternator pulley diameter?
It may be a smaller pulley will up the alternator RPM and solve your problem unless there is a discharge somewhere that is draining down the system.
Your battery should be under 14V, but above 13V.
With the negative battery terminal disconnected, attach a light between the negative battery post and the disconnected negative battery terminal at the end of the cable.
Does the light filament glow with all electrical devices switched off?
Test light glows on initial contact but then immediately goes out.
Battery is your problem. Throw a charger on it. Just sitting there, a healthy battery should be at like, 12.4-12.8v. Assuming you don't have a slow drain. If you have a lead acid battery, check the wells, make sure you've got water in there.
Also some batteries don't start making a legit charge until 1200 rpm or so. So keep that in mind.
Do a cranking test. What is your voltage when cranking? If it drops to like, 4-5v, then yes your battery is crap.
Put the charger on the battery for a few hours & it went back up to 12.25.
Ran tests again with results slightly higher but still under 12v at idle. Alt reading is about .1v lower then battery.
Battery is a Napa Legend and seems sealed rather well.
Crank test dips 10v and catches quickly.
Will pull both battery & alt to have checked at Napa.
To make it even more interesting she runs rough between 2000-2500rpm.