The Stovebolt Site Forums The Shop Area The Electrical Bay High voltage Problem 16-18 Volts

Overvoltage problem I have a 53 1 ton with a 292 engine. Previous owner converted it to 12 volt. It had an aftermarket gauge cluster installed, Temp gauge, amp meter and oil pressure gauge. The oil pressure was the only gauge working, so I replaced it with another cluster only with a voltmeter this time. Temp and Oil gauges work fine but the voltmeter was zapped by a high voltage and stuck at 16 + volts. I replaced the voltmeter with a better grade meter but it still reads about 16 to 18 volts. This gauge is wired positive off the ignition switch and other side to ground. I thought that the regulator in the alternator was defective so I replaced the alternator. Still the same problem, I might mention that the low beams were both out when I got the truck, high beams were OK. I think that the higher voltage might have blown them. The only thing I can think I can do is trace the wiring and see if there is anything I can find there. Anyone have any ideas on what is causing this? Thanks in advance

grain truck,

I think the alternator will put out until it is told to stop. While it might sound like a regulator problem, that theory went south with the "new" alternator.

My only thought would be it isn't getting a good 'sense' of the system voltage, and keeps on humping.

I would check where my #2 wire was connected. You could always try putting it on the alternator power lug and see if that does anything.

The regulator should do just that. Two bum alternators in a row is pushing the odds. It sounds like it is something else.

Have you checked it with another meter, maybe a good VOM.

I wonder if the alternator has a good ground back to the battery.


Stuart

What does the voltage read on the positive battery post itself? Do you have a three wire alternator and is the sense line properly attached if you do?

It sounds like you're sure the regulator is in the alternator. Just checking. The 3-wire alts with the DA plug like (- -) has an internal reg, and the if the plug is like (| |) you should have an external regulator. On the internal type,like Stu says, the # 2 (voltage sensing wire) should go to your main power bus bar.
On late 60-70's model Chevy's, this is located somewhere on the drivers side, and sometimes on the horn relay. It typically is a cluster of 4 (or more wires). Chevy senses the voltage here to compensate for voltage drop on long wire runs under heavy load.
Regulating the voltage right at the BATT term on the alternator would NOT result in higher voltages, just a little low sometimes when the battery is low. Which is not a bad thing. It is more gentle on the battery to charge slowly.
Dave

Thanks for the replies. I checked the truck this morning and you were right Dave, to my surprise it has a regulator on the firewall.
A dumb mistake on my part, I should have known better as I am old enough to remember the old 6-volt systems with a regulator. Now how do I check to see if the regulator is bad or can it be adjusted or not. It has a 4 wire plug going into it marker F 2 3 4 and a condenser plugged into the bottom. Again, Thanks all for the help this is a great website and I have learned a lot from it. Just hope that someday I can help others with there problems.

I take it you have an alternator that uses the external regulator. You canput a voltmeter on the battery terms or junction block. It should read at or close to 14 volts with the engine a little above idle. If its high you can remove the cover from the regulator. The voltage side is closest to the F term. See if the points are stuck. If it,s the original equipment Delco there is a screw by the base to adjust the voltage. If it is an aftermarket you have to bend the tab that the spring attaches to. Be very careful, one short or wrong move & puff of smoke it,s all over. After you foul it up you go buy a new one.

Your high voltage could be caused by a bad regulator. Before replacing it, I would check all your grounds. Check voltage from battery neg post to the engine, frame, firewall and most important, the regulator itself. These readings should be around 0.2 V or less. If the regulator is mounted on three rubber feet, it must have a separate ground to its base.

Fla'da boy this could be the same problem you are having.
The internal reg on your SI-10 or SI-12 is held in place with three screws. Two of them are tied to the brushes for the rotor. The third screw is the ground connection for the reg. If this screw is loose or making a poor connection, the reg is floating electrically above ground and can not control the current to the rotor and therefore can not control the alt output.

As Wrenchbender said, check the voltages and grounds with the engine running.

Good point Richard. If the regulator is not grounded it will charge infinitivly.

Maybe I misread the last few posts. I think he has indicated he has a SI alternator wired in series with a voltage regulator on the firewall.


Stuart

I repaced the regulator with a used original Delco and it was still reading high so I adjusted it as Wrenchbender Ret. suggested and it now is set at about 14 Volts. Still not sure it is completely fixed but I am making progress. Now on to the next project, adjusting the drivers door. that's for another forum, it never ends does it? I guess that's what keeps us going. Thanks again for the replys, Ralph