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My 7 year old battery didn't hold a charge after a few days of sitting so before I get a new one I wanted to check whether the issue is really my charging circuit. I suspect it's a failing 7 yr old battery but why not check? I charged up the battery, started the car, and measured the voltage at the battery and was surprised to see 16.25VDC. I know the voltage should be around 14 VDC when at a fast idle and about 13. 5V at normal idle so what is going on here. Is the charging circuit capable of providing 16.25V or is my regulator faulty?
Assuming your alternator hasn't been changed to an internal VR & you're using the OEM VR (or it's equivalent), the part numbers are listed below in the 1972 PIM (1119515 or 1119519)
I believe 35C49 is the optional rear window defogger - not sure. You'll probably find a number on your VR anyways. Thought this may assist.
May be able to swap the VR cover old to new for original look. A different spin on the cooking the battery question ...Did the 7 year old battery overwork a marginal charging system? After replacing the battery, VR and confirming the correct voltage output have the amperage output tested.
Replace the battery and retest. A bad battery can cause an overcharge condition.
This goes back to my original question - is a properly functioning voltage regulator supposed to produce 16.25V if the battery is faulty? I thought if it was functioning properly it would only produce a max of ~ 14.5V.
This goes back to my original question - is a properly functioning voltage regulator supposed to produce 16.25V if the battery is faulty? I thought if it was functioning properly it would only produce a max of ~ 14.5V.
Alternator overcharge is caused by a defective VR >95% of the time. Replace the VR & retest the battery after VR replacement. Your reading at the battery w/ a new VR running & charging the battery should be between 14.2 - 14.6 (optimally). A defective VR yields an uncontrolled increase in alternator output. I would not drive the vehicle until the VR is replaced since this can increase the buildup of heat in the battery.
Didn't drive the car. The battery I charged up last night to do the voltage test was flat so I think it's toast. Got 7 years out of it so I can't complain. Replaced the VR (replaced the gray cover on the new VR with the old VR black ACDelco cover too ) and put in a new battery. 14.4V at the battery at idle so all appears well now.
Thanks Norm and all for your help. Now we'll see how long the solid state VR works...
Good news and good work! The charging system should also be checked for amperage output. Correct voltage is a necessary component but isn't the complete picture.
) and put in a new battery. 14.4V at the battery at idle so all appears well now.
