Charging issues
 

I have a new alternator and voltage regulator and all my wires seem to be good but with the engine running voltage at the battery is only 12 volts. I took the alternator back to Auto zone to have it tested and they say it is good. I can put my meter on the post on the back of the alt. With it running and it still only shows 12 volts. Any advice on what to do next?

Re: Charging issues
 

put this in the electrical section, you will find good people there that know their stuff.

Re: Charging issues
 

Just measure across the battery and post the voltage (to the nearest tenth, as in 12.6V) not running, running at idle, and at a few thousand RPM.

Re: Charging issues
 

It sounds like either the alternator or the voltage regulator. These days, buying new parts does not necessarily mean that are going to work correctly.

Re: Charging issues
 

I had the alternator and voltage regulator tested at the local auto electric shop and they both tested good. I guess I will check the wiring next . I glanced at it and didn't see anything obvious.

Re: Charging issues
 

Might be obvious, but is the belt tight?

Re: Charging issues
 

I tried to get a regulator tested and they told me cant be done

Re: Charging issues
 

Yup, the electrical guys will probably show you a wiring diagram of how it is supposed to work. I suspect you are not getting voltage to somewhere on the regulator or on the up side the regulators for these things are dirt cheap. Mine was overcharging and from someone on this forum I found that it was probably a bad ground between the regulator and alternator and it was. In the end I had an extra alternator with internal regulator which I used and donated the original to a local re-builder.

Re: Charging issues
 

Is the regulator grounded?

Re: Charging issues
 

Pull the small plug off the back of the alternator and check the white wire with your meter. Key off--zero volts Key on--12 volts.

The blue wire should show 12 volts with the key on or off.

Make sure the alternator is grounded, the regulator is grounded to the shroud and connected to the alternator.

Attachment 1739209

Re: Charging issues
 

Have you checked all your grounds?

Re: Charging issues
 

Take the connecter off the regulator. Put a jumper wire from the blue wire connector to the red wire. You should get a small blue spark when you make & break the circuit. Start the engine & check the voltage. If the voltage goes up it means the alt. is good & the problem is in the reg. or wire ing.

Re: Charging issues
 

Check the tension on the alternator belt. Also double check your grounds. I would suspect the alternator over the regulator. But you said that tested normal...

Re: Charging issues
 

Well here is my 2c...

Make sure the regulator is getting ignition signal (and batt., & continuity to alt.) - I had one that had a faulty wire

Also while revving up the engine a little, ~2000-2500 rpm, check voltage- if it rises to ~13.5v then it may be as simple as a wrong size pulley

If all else fails replace the regulator - I think they are pretty cheap and it would at the very least eliminate it from being a possibility

Re: Charging issues
 

In the photo posted by VetteVet, it appears to be a Delco 10SI. Identification is crucial first, but if this is your alternator, the regulator is internal AND yes, it has to be grounded. Use the un-used threaded bolt hole and provide a 10 AWG to the engine. I like using star washers on eyelets. The top connector has a small "D" shaped hole under it as pictured. The regulator provides ground to the stator, this is a test window. With engine running, carefully place a pocket screw driver into the hole to touch the case & tab from the regulator. Rev up the engine as you should hear a little whine. Your DMM should show 13.8 - 14.2Vdc. Let's figure out what you have first and what you need to do. The "F" terminal is hot thru the key on, going thru the charge lamp. Depending on the year, they place a 460 ohms resistor in parallel with the lamp to maintain the charging circuit if the bulb goes out. The field coil is the "Y" connect type. The center connection has no voltage if not working. When it is running & working, it provides B+ to the dash lamp. With B+ on both sides of the lamp, it goes out. If their is issues with a diode or something in the alternator, the lamp comes on dim. I have used this terminal to run the electric choke.
Do you have a DMM or analog meter? Are you looking at the dash gauge or meter? Are the battery cable ends clean where the sun does not shine? Are there good ground cables from the battery to engine & chassis? Let's start there with some answers. I taught 31 different classes, 6 of those being electrical classes for ACDelco, with #6 being lab scopes.
As for wire size (AWG) yes, current is measured in amps, but the length of the circuit determines the size of the wire. Most 4 -10 amp circuits operate with 20 gauge wire on GM's the last 30 years. As for a good relay/fuse center, go for the passengers side IP relay center from Buick LeSabre, Park Ave thru 1990-1999. Older one had 0.250" relay terminals, then they switched to "Micro" relays using 2.80m or called 280. The relay/fuse center is behind the glove box, with the ECM, theft module (Pass-key) and lamp module and is rectangular in shape while locations for 12 relays & 12 fuses. Good bone yard find for $10 of less.

Re: Charging issues
 

The alternator I pictured is a 10 DN used on 67 to 74 gm vehicles specifically our
trucks. They use an external regulator as the OP states that he has. Converting to an internally regulated alternator 10/12 SI is very easy, or even up to a CS style. I've detailed the conversion many times her on the forum.

The internal regulated alternators do not require a separate ground like the one I pictured since the regulators are grounded to the alternator case. Grounding is managed just by bolting the alternator to the engine block with clean mounts of course.

The instructions in post 12 by Wrenchbender Retired, will full field the alternator, and a voltmeter connected as instructed should give a reading of up to 16 volts. The small D shaped hole in the 10 dn will also full field the alternator if a small screwdriver is inserted. Only do this for short periods less than 30 seconds, because it will overheat the alternator. Also it may over voltage and damage any loads in the circuits, so do not rev the engine with any lights on and do not rev the engine if the HEI distributor has been installed. This especially includes any digital goodies that are sensitive to over voltage.

Pictures of the 10 and 12 SI alternators.

Attachment 1745700

Re: Charging issues
 

Thanks for the info guys. I haven't fixed it yet but I am going out this afternoon to work on it . I have the old style alt. with the ext. reg.. Are they grounded when you bolt them on or is the ground wire from alt to reg required?

Re: Charging issues
 

I went out and started looking at wiring and connections. I took the red wire that runs from the battery to the other side where the regulator and horn relay are loose and wire brushed everything , put it all back and started it up. When I stuck my meter on the battery terminals it showed 14 volts . Must have been bad connections. Sometimes you overlook the simple things. Thanks for the advice.