Application: 1966 Riviera I'm trying to diagnose an overcharging problem in my Riviera. Alternator is two years old and I recently had an electric motor shop look at the alternator because it was not charging. They found a bad brush holder and repaired. Bench tested and good now. Installed back in the car and now it appears to be overcharging. The alternator gets very hot and according to my voltmeter is sending almost 17 volts into the battery. I tried replacing the regulator with a new one with no difference. ( I have heard that the new regulators can be junk). Here has what I have done so far. 1. Checked all connections at the alternator 2. Removed and cleaned negative and positive battery cables at both ends. 3. Test battery and has 12+ volts. Had Napa test battery it is good. 4. Had a shop test the battery in the car while running for current and is showing 15amps when running. 5. Removed and checked the old Voltage regulator points for operation and cleaned. 6. Removed all cables at the horn relay junction block and cleaned. 7. Inspected all ground cables for corrosion and tightness. I suspect the external voltage regulator is bad but not sure. The new one did not help but I don't know how to test a regulator to see if its working property. Alternator is putting out plenty of juice, over 16 volts. On my car, the horn relay is part of the wiring junction block. Horn relay is only making a clicking sound when I push the horn button. Could a bad horn relay cause my overcharging problem? Any ideas would be greatly appreciated. I am seriously considering upgrading to a 12si internal regulated alternator. But if that doesn't solve the problem I'm not sure what to try next. I did call the electric motor shop and spoke to them about my situation. The gentlemen suspected a bad battery. He also said that something in my system is telling my alternator to provide maximum output. This shop is full of old timers and they fix 100's of starters and alternators every year. I trust them but no one is perfect. Thank you. J.R.
I harp on it, but it is basics, and most problems are from the simplest cause. Grounds, and supply connections. Loose connection can cause high charge condition as the alternator is being called to charge, but the bad connection/resistance does not allow the battery to be charged, and the alternator will overheat and start burning off the enamel on the windings and alternator failure. Bad connections can also result in a continual overcharge state where the regulator does not sense (solid state) or physically regulate (electromechanical) the charge state and cook a battery. Check clean and proper connections, correct AWG. You must have proper battery clamps and clean/fully engaged/seated to posts and tightened properly. Over tightening clamps lead to bad connections. Oxidation leads to high resistance. Minimum is: Negative post to block. Block to frame. Block to body. And post to frame and body with 10 AWG is good extra bonding. Positive should go to starter, or through a lug to the to the starter. And the wiring from alternator and regulator connections and terminals need to be solid. Old wiring becomes more resistant to current flow due to break down of insulation, corrosion of terminals and the bond to wiring, even soldered joins, and the corrosion that builds up on the strands from oxidation that you cannot "fix" inside the jacket. 50+ year old wiring is asking for a wire fire.
Make sure V-reg is grounded. Pull reg plug out and test to see if it has the same voltage at terminal #3 as the battery. It is not common for a brush holder to go bad especially in only 2 years. There may be a problem with the rotor. If the reg ground is good and you have 12 volts at #3 on the reg plug, have the shop take another look at the alternator and ask them to test the rotor amp draw and for a grounded winding.
Steller, I can complete the test you suggested. How is the VR grounded? I just assumed it was grounded by the mounting screws. I think I damaged the brush holder when I tried to re-clock the alternator. It went back together much harder than it should have.
It should be grounded by the screws. As the shop said a battery could also cause over charging. I suppose you could have 2 bad regs, but both doing the same thing seems unlikley, but not out of the realm of possibilities. Start the car and when it is over charging pull the rge plug out. If it continues to over charge have the alt looked at.
Good news! I have solved the problem. Turns out the new regulator was bad as well. I went with a solid state regulator this time and ran a separate ground strap from the base of the new regulator. Volts when running now 14.25. Ammeter steady as can be. Ran for 1/2 hour and alternator did not heat up. Thanks for your help stellar and Mike, I really appreciate it. J.R.
J.R. -use actually have an Ammeter? Thought they went out when cars went from generator to alternator when u need to know the draw on the generator.
Yes on the Ammeter. 1966 Riviera might have been the only Buick model that year that still had an Ammeter. Not sure what year they phased it out. Most models had a warning light. Not sure when the voltmeter was introduced.
