I took the 68 out for a drive last week and noticed the GEN needle was almost pegged to the right (charging) rather than the normal position of being dead center between D & C. A little later I discovered every time I used something electrical (brake, directional, parking lights) the needle would wiggle and then settle back to its original position.
I assumed my voltage regulator was shot so I replaced it with a solid state VR from Ames. Started it up this morning and it did the same thing - needle very far to the right and it wiggles when I hit the brakes or put on a directional. I have a multi-function timing gun which reported 16V into the battery. Not sure what to do next?
First don't drive the car as over charging can cause a battery to explode.
You need to get a DC voltmeter and recheck the voltage at the battery with the motor off and running, off should be @12VDC and running should be @13-14VDC, you said a timing light said 16 but let's get a real meter and check.
It is possible you got a defective regulator from Ames, they have a couple of different ones, one is a China copy of the old points type and one is solid state, you could take your old one apart and see if the points/switch are stock closed, maybe force them open and reinstall or disconnect the regulator and start the motor and check the battery for power, if it's got 16 with the regulator unplugged something very weird is going on, like someone changed the altenator to a modern one and it's gots it own regulator and it's bad and your old regulator was just there doing nothing.
Thanks for sharing some thoughts. I was going thru an old Chilton's Firebird manual last night which stated the "normal" output voltage rage of a Voltage Regulator was 13.5 to 16V and in my situation the voltage never exceeds a 16V reading, no matter how high I rev the engine. I always thought the target charging range was 14.5V, more in line with your range.
I must admit I never thought of the possibility that the alternator had an internal VR. Is there an easy way to check (ie like not disassembling the unit)?
I wouldn't go by old manuals for that, once you get near 15V your battery will start off gassing and become an explosion problem child.
At some point not sure if it was 1970 but most cars started coming with alternators that had internal regulators, some guys put these in old cars by choice or mistake but it would still have to be rewired to bypass the original regulator, you'd have to compare wiring diagrams, usually they run a 10ga wire from the alternator to the battery. If that doesn't exist then the probablity is that you got a defective brand new regulator.
Got it. I'll call Ames tomorrow morning and get their take on the VR. Does the solid state VR need to be grounded? The conventional one I replaced had a ground wire connected to base running to the chassis. I notice the new one did not have a ground screw.
Could be your new regulator is defective as well as the old one. Could be the battery is defective resulting in the alternator putting out that much voltage to sense 14 at the regulator. Could be dirty connections at the regulator.
The regulator has a voltage sensing circuit, it's terminal 3 on your regulator and is connected to the main splice via an orange fusible link wire. It senses voltage in the system and if it's low the regulator flows current to the alternator field which increases alternator output to raise the voltage. If you have a draw somewhere in the system that is causing a low volt reading at the sense wire it will cause the regulator to up the voltage output of the alternator. The alternator could be putting out 16 volts just in order to maintain 14 volts at the cause of the voltage draw. Check the voltage at the + post on the alternator as well as the pos post of the battery to see if they are the same. Then check the voltage at terminal 3 of your regulator, There may be a voltage drop between the main splice where the sensing wire should be connected, and the connector at the regulator.
The battery cables are very clean with zero corrosion. I disconnect them when I am not running the car. All the wiring harnesses were replaced during the restoration so I don't suspect dirty connections at the VR. I have no idea how to test if the battery is defective or not?
I tested voltage with a meter at the 3 locations you suggested: 18.2 V at the battery 18.2 V at the alternator + post 18.2 V at terminal 3 at the VR
So if I understand the test you suggested, since there is not a voltage draw between the alternator and VR it then shifts focus back to either the battery, alternator, or VR? Since the VR swap did not really change anything is an alternator swap next?
I assume 18.2 volts is with the engine running, what is the voltage with the engine off? When you step on the brakes or turn on the signal lights the needle goes to the center of the gauge. Does the needle go right back up to full charge when the brakes or signal lights are off? Does the needle go to center when the heater fan, head lights or wipers are turned on? I'll have to think of why the regulator would quite over-regulating when the brake lights are on, maybe somehow grounding the sense?
Did this snag happen suddenly, was normal operation for weeks or months then one day overcharge? Was there rally gauges before the restoration or was it an idiot light cluster converted over to gauges?
The alternator should only put out as many volts as the regulator allows it to. There could be a failure within the alternator that is supplying extra flow to the field circuit and thus more voltage output, but I would think it most likely to be the regulator supplying too much to the field for some reason, either sensing a low voltage due to a wiring problem and upping the field or a defective regulator. You could take the alternator to a parts store for testing, the NAPA near here does it for free.
Yes the regulator should be grounded, don't know if the solid state ones ground through the case and the mounting screws/bolts or if there is a screw on the back that a ground wire attaches to.
I've heard of solid state regulators causing overcharge conditions when replacing a points/coil type.
Yes, the numbers above were when the car was running. Here are the number when the engine is off:
Battery 12.76V Alt + stud 12.76V VR #3 post 12.76V (new solid state still installed)
With the engine still off, and nothing engaged the GEN needle is perfectly centered between D and C.
When I then step on the brake pedal the GEN needle swings quickly once to the left and then settles slightly on the D side of center. It stays that way (ie fixed to the left of center) for as long as I keep the brakes engaged. Same exact result for parking lamps, emergency flashers, and headlights.
With the engine off but accessories enabled I turned on the wipers and got a different result. They needle did not swing, it just moved slightly to the left to indicate the draw. Needle stayed that way for the duration until i turned off the wipers. Same exactly result for the blower motor, no needle swing, just a larger move to the left due to what I assume is a larger draw.
Concerning when it started: Car has been running fine for about a year, just came on without any electrical modifications. I added the rally gauges during the restoration. They are stock, not aftermarket. When I received them I sent them off to a company i found in Hemmings to clean and calibrate. I did not modify my existing wiring harnesses, they were pretty rough so I installed new ones (from Ames) during the restoration to avoid electrical problems (how ironic, right!).
The VR did not have a grounding post but I tested it earlier while getting the readings above and it is grounded. I use the rubber seats when installing, it appears to be grounded on a core support ridge. I will ground it with a wire in case the grounding thru the core support is unreliable when running (due to engine vibration).
I have a NAPA and Pep Boys about 20 min from the house. I am sure one of them can test the alternator as you suggested.
So I made some progress and wanted to share it with some fellow Pontiac enthusiasts out there.
I pulled the alternator from my next project, a 68 GTO, and now get 14.1V with the firebird engine running. GEN needle no longer moves as I rev the engine. Best part is that the alternator I pulled from the GTO had a 22 April 1968 date code on it and it still works!
Also, I spoke with a Wise tech about their VR715 voltage regulator & how hard they are to find. Tech said Wise is getting back in the VR business April/May 2020 timeframe. He said most of those sold as Duralast but supposevly manufactured by Wise are cheap knock-offs. He also said the solid state VRs MUST be grounded before power is applied or they frequently short.
So, last problem I am chasing - with the engine off I depress the brake pedal and the GEN needle swings once (very fast) to the left and then settles slightly to the left of neutral. Stays that way for as long as I keep the pedal depressed. Same for parking lights - fast swing to the left and then settles to the left of neutral.