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Not getting voltage from alternator..baffled


astrochimp

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So the alternator and voltage regulator are pretty new and have very little mileage on them. I've done a continuity check with wiring..seems fine.

When it's running..my dash gauge shows 12 volts and testing voltage at the battery shows 12 volts.

Here is a photo of the voltage regulator and all terminals show about 12 volts except the white wire is giving me about 3 volts?

 

any thoughts, ideas, ammo would be helpful

 

Thanks

post-50-0-90103500-1470682616_thumb.jpg

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1st the regulator should be grounded. second you can unplug regulator & jump out labeled wires F & 2 start it up slowly & increase RPM voltage should rise fast Don't go beyond 16 Volts 1500 RPMs if it does it's regulator or bad wiring or ground. There are many test you can do but too much to post here get a repair manual if needed normal alternator output should be at least 13.5 to 15 volts depending on Temperature & load, Rpm's. Bob

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I think through the capacitor that is hanging off to the side. The regulator is supposed to bleed off excess voltage. With out it grounded it cannot do its job.

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Definitely ground it to the frame somehow. Check for voltage like LastSS mentioned. If you are not getting anything there than the wiring from the Alt. is bad or the Alt itself is bad. I added an internal regulated alt. and bypassed the regulator on mine. problem solved. 

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You can also take Alt to any Advance or Autozone to machine test it, It's Free. Only a 5 min job to remove, Check plug-in 2 wire they make a replacement repair connector $5.00 Make sure you Always disconnect battery whenever you work on Electric.

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I have a 71 350 4BBL with a total factory gauge package I swapped, including ALL the wiring, from another 71 350 4BBL.

I did this swap over 27 years ago.

Several years ago I started to have problems, it wasn't charging and when I turned on the headlights, the gauge went negative.

I replaced the regulator and I it started charging again.

This spring, the 7 year old battery was dead. I bought a new one and it started up great. I noticed it wasn't charging!

I messed around but decided to take it to a place that does electrical near my home that my brother in-law uses.

The owner looked at it, did some things with the wires, said the alt was charging fine, did some more stuff, said it was fixed, I gave him $20.00.

Got home, the gauge was to the right, my miss at high RPM was gone! I washed the car, started it and noticed it was no longer charging!

Took it back, he did some more stuff, said it wasn't getting power from the dash brown wire. He found a ign on hot wire from the no longer used TPS, teed into it ans my problems are gone.

The real problem was NOT repaired. I believe it may be in the IP wiring or printed circuit. I remember several years ago, messing with the after market left ft speaker and it partially pulled out the IP connector. I didn't mess with anything this year dash related but did wipe the dash pad and clean the inside of the windshield very well. Perhaps that did it???

Bruce

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All good information!

 

Anybody know Exactly what each terminal does on the voltage regulator? I'd like to understand the function of the thing so I can trouble shoot it better in the future.

 

 

THANK YOU!

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about to go jump in front of a bus..

so i had the voltage regulator off the mounting position laying on the frame inside the engine bay with the capacitor on...didn't mess with it for a day or two, then I sand some connections and screw it back it to try and do some trouble shooting and I Can't turn the engine over because the Brand new battery is Completely dead.

 

have no idea what happened..the wiring at the battery terminals is stock. they keys weren't in the ignition.

AND my craftsman multimeter is going nuts, showing voltage with NOTHING even connected to it(side issue )

 

charging battery..going to get a new multimeter..then going to check for current leaks.

 

definitely not winning

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1st the regulator should be grounded. second you can unplug regulator & jump out labeled wires F & 2 start it up slowly & increase RPM voltage should rise fast Don't go beyond 16 Volts 1500 RPMs if it does it's regulator or bad wiring or ground. There are many test you can do but too much to post here get a repair manual if needed normal alternator output should be at least 13.5 to 15 volts depending on Temperature & load, Rpm's. Bob

This was the key ingredient right here. So I pulled off the voltage regulator with the attached capacitor and did this test.

The voltage did go up.

So holding the voltage regulator I then removed the jumper and plugged in the 4 wire cable into it.

The voltage went back down to about 12 volts. The interesting part is I'm still holding this so it's not mounted to the car and I rev the engine a couple times and THEN the voltage jumps back up to 14 volts. I unplug it and it drops then i plug it back it and it goes to 14.

SOMEHOW revving the engine is making the voltage regulator work but of course I'm going to get a new one.

Didn't realize these things are actually mechanical with contacts inside of them.

 

Nice to learn something new.

THANKS TO ALL

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I had all kinds of issues finding a voltage regulator that would work for any period of time. I would get them bad right out of the box, or get one that would last a month or so before failing, so I changed over to an internal regulator. Ever since I swapped the system, I haven't had any weird regulator charging type issues.

 

I know some folks want to keep originality, and that is understandable. I just wanted to share the fact that lack of good, dependable replacement parts drove me to change to an internally regulated setup.

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Yeah, i think in the near future i have to convert this to internal.

So i bought a new voltage regulator and STILL not getting voltage from the alternator.

The last thing i can do is get the alternator tested i guess.

I checked the junction block behind the battery and cleaned it up.

I Don't understand why revving the engine triggered the alternator to kick on last time. Now revving the engine doesn't work.

Hoping it's the alternator, We'll find out.

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I had several regulators bad right out of the box. Another reason I changed to the internally regulated set up. Easy enough to get the alternator tested, and then you'll know for sure.

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Testing the Alternator

A test we call the Full Field Test involves applying battery voltage to the alternator field terminal.

Start with the engine off.

Disconnect the alternator field wire coming from the regulator.

Attach a voltmeter to the positive output terminal of the alternator. It should read battery voltage.

Prepare a short wire with a terminal on one end which will connect to the alternator field wire.

Strip the other end of the wire about 13mm leaving it uninsulated. Do not let the bare end touch anything.

Start the engine and increase it RPM to about 1200.

Expect some sparks at the end of the next step.

Momentarily touch the bare end of the wire to the positive output of the alternator.

A good alternator will charge at maximum rate. Battery voltage will rise, and the engine RPM will decrease due to the load.

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^that's some great information..wish i read it sooner.

I won't go into Full boring details but I went through and continuity tested, ohm tested and voltage tested all of the connections to and from the voltage regulator and to from the alternator. I also kept swapping out my older mechanical voltage regulator and this new (solid state I think..no clicking inside) voltage regulator.

 

I ran a ground line to the case of the voltage regulator right to the battery.

 

I get a field voltage with the key turned to ACC but engine not on. Ok, seems good. I start the car and voltage doesn't move on the battery.
So, with EITHER regulator, i still have to rev the car RPM's up to get the alternator to kick on and start working. ( is this something internal of the alternator that requires the rpm's to go over a certain amount?)

 

I did notice that the ACC (i think it's connector 4) on the voltage regulator is NOT 12 volts when the key is turned..more like 10 or so.

I wonder where the OTHER end of this wire is located and if it's a junction block somewhere, maybe I should clean it.

 

So this Seems to work for now.

 

this was some helpful info

http://www.hyteware.com/1966_chevy_c10_electrical.php

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i remember having similar issues years back. i belive what i ended up doing for a fix and piece of mind was making a big ground loop. starter- battery-block-frame-trans.

im not saying its a fix but its cheap insurance and takes maybe 30 minutes

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  • 2 weeks later...

There is the excite wire to the alternator..but what does the OTHER wire do that is connected to the plug on the alternator?

 

Everything seems to be great now with the car...SOOO glad i ripped out all the nonsense electrical and went with HEI.

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There is the excite wire to the alternator..but what does the OTHER wire do that is connected to the plug on the alternator?

In order to complete the circuit the field circuit must go through a resistor. This lowers current output, points close, output increases, points open, output down, points close, and so on. You could say it's the monitor in the system. That's my take, voltage regulator theory I'm sure is much more complicated than that.

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