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Varying Electrical output

Dan Hunter

Dan Hunter

Truck Terrorist
Messages
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Location
Enid, OK
OK, I've checked the charge on my batteries and my terminals are clean but over the last couple days, I've been seeing odd indications. at idle, the thing indicates about 11 volts and at speed indicates about 15-16 volts.

Have I lost the voltage regulator in the alternator?
 
Dan Hunter said:
OK, I've checked the charge on my batteries and my terminals are clean but over the last couple days, I've been seeing odd indications. at idle, the thing indicates about 11 volts and at speed indicates about 15-16 volts.

Have I lost the voltage regulator in the alternator?
Click to expand...

Could be a bad voltage regulator since as the alternator is "winding up faster" so to speak it making more energy. No regulator would allow that. Could be a bad gauge as well but you can double check by disconnecting the alternator from the electrical system, then reading the voltage coming off the terminal on the back based on engine speed. That will tell you right there.

Best get it fixed sooner rather than later as to high of a charging voltage can damage your charging and electrical system.
 
That could just be your sending unit sticking. Mine seems to do that for whatever stupid reason. Gets your hopes up cause you've gone like 150 miles and barely eaten an 1/8th of a tank, then you hit 300 miles and all of a sudden your at half a tank. stupid sending unit :mad2:

Of course, it could be ground related as well. Whats the condition of your grounds?
 
BigBlueChevy said:
That could just be your sending unit sticking. Mine seems to do that for whatever stupid reason. Gets your hopes up cause you've gone like 150 miles and barely eaten an 1/8th of a tank, then you hit 300 miles and all of a sudden your at half a tank. stupid sending unit :mad2:

Of course, it could be ground related as well. Whats the condition of your grounds?
Click to expand...

yeah and it just keeps dropping faster as you drive on the tank.
 
My bay has always been relatively clean and my grounds sound. Terminals have been a problem but again I checked 'em.

It's funny. The voltage drops as you hit the brakes at low speed and the rpm drops but comes back up when you take your foot off and goes to about 15 with the throttle up. I just don't remember seeing such movement in the past. The only time it would drop that much is the crossover wasn't sound but that's not the case this time.
 
Dan Hunter said:
My bay has always been relatively clean and my grounds sound. Terminals have been a problem but again I checked 'em.

It's funny. The voltage drops as you hit the brakes at low speed and the rpm drops but comes back up when you take your foot off and goes to about 15 with the throttle up. I just don't remember seeing such movement in the past. The only time it would drop that much is the crossover wasn't sound but that's not the case this time.
Click to expand...


Funny you mention that. Back during last summer I put up a post about how my RPM gauge was fluctuating as well. It wasn't all the time, but every now and then it would dip down, but engine speed and sound would remain constant. I pulled the alternator, thinking it was time for replacement and brought it to PepBoys. I must have drove the guy nuts cause I had him bench test it 3 times, and every time he said it was operating normally. Brought it home, cleaned the terminals to a shiny face, added anti-ox paste and bolted everything back up. I haven't had an issue since.

The cheapest and easiest fix is just taking a half hour and cleaning up your connections on the alternator. You may find that's your issue.
 
I agree, clean and check everything. one note of major caution, if you do need a new alternator do not, DO NOT get one from autozone. I have gone through 4 "gold" series. bad bearings mainly, but others here have noted as I, as they warm up voltage goes to 12.8v. pour cold water on em and voltage goes up. I am waiting to get money for a real alternator and take the garbage back.

lifetime warranty does not help when it locks up in downtown Houston.
 
To clarify, I meant the rpm dropped the idle speed dropped...natural I believe. The point was the low voltage.

I put a meter to it at both batteries and both at idle and at 1500rpm, the output seems normal with the alternator providing about 14.3 volts average between the two terminal sets at 1500rpm.
 
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