Alternator & Voltage Reg? (My 1st 67 project)

[GreenBay1921]

I've been working on a 67 C10 SWB that I bought just before Christmas. It has been sitting since 92. I've been able to get her running & stopping, but she still needs some tweaking & lots of work. I haven't worked on anything (besides brake jobs & oil changes) for nearly 20 years. So try to bear with me guys, I'm not as good as I once was .... So my question is: I have the engine running, but when I take the battery cable off she dies. I know this usually means alternator is bad, but I don't know much about a voltage regulator . Should I just get a new alternator & voltage regulator, or is it more likely just the alternator? Thanks guys.

[VetteVet]

pull the plug off the alternator and check the two wires with a voltmeter.

The blue wire should read 12 volts with the key on or off the white wire should read 12 volts only while the key is on. If it reads 0 volts either way then your regulator is bad, if it reads 12 volts with the key on then chances are the alternator is bad.

You can also jump the regulator by connecting the brown wire and the white wire on the regulator and IF the blue wire has 12 volts at the alternator the alternator should go into full charge mode of about 16 volts. Do not leave the jumper on for more than a few seconds and be sure that the lights are off and the engine is at idle. You can tell if the alternator is charging by connecting the volt meter between the large lead on the alternator and the engine block or other good ground. If you read high voltage then the regulator is bad. If you read no voltage the alternator is bad internally. Don't forget to plug the blue and white wires back into the alternator.

If you decide to go with a newer style alternator SI or CS then the conversion is very simple.

[GreenBay1921]

Originally Posted by VetteVet

pull the plug off the alternator and check the two wires with a voltmeter.

The blue wire should read 12 volts with the key on or off the white wire should read 12 volts only while the key is on. If it reads 0 volts either way then your regulator is bad, if it reads 12 volts with the key on then chances are the alternator is bad.

You can also jump the regulator by connecting the brown wire and the white wire on the regulator and IF the blue wire has 12 volts at the alternator the alternator should go into full charge mode of about 16 volts. Do not leave the jumper on for more than a few seconds and be sure that the lights are off and the engine is at idle. You can tell if the alternator is charging by connecting the volt meter between the large lead on the alternator and the engine block or other good ground. If you read high voltage then the regulator is bad. If you read no voltage the alternator is bad internally. Don't forget to plug the blue and white wires back into the alternator.

If you decide to go with a newer style alternator SI or CS then the conversion is very simple.

Thanks. I'll run the procedure tomorrow. What is the newer style? Is the regulator built in or something?

[VetteVet]

Originally Posted by GreenBay1921

Thanks. I'll run the procedure tomorrow. What is the newer style? Is the regulator built in or something?

Yes that is correct.

You may find this informative.

......http://67-72chevytrucks.com/vboard/s...d.php?t=417872

[RichardJ]

Pulling the battery cable OFF on a vehicle with an alternator, isn't the way to see if the alternator is broken, it's a good way to break the alternator.

You said the engine is running so just connect a voltmeter to the battery and see what the charging voltage is. As long as it's above battery voltage at idle or 13-14 volts at a high idle it's good.

If the alternator isn't broken and you didn't manage to break it, leave it alone. Unless you have plans for adding a ton of electrical accessories, the original 10DN alternator will outlast any SI or any ten CS alternators.

[franken]

Better to get a dvm or voltmeter and measure the voltage on the battery. Check with engine running and not w/ key on.
More rocket science.
The point being, you should learn about how the truck, or electrical systems work, rather than shotgunning parts. Same with other systems on the same truck.

[GreenBay1921]

Thanks guys. I'll go through the procedures as suggested later today, & post the results. I appreciate the input.

[67 chevelle]

Originally Posted by RichardJ

Pulling the battery cable OFF on a vehicle with an alternator, isn't the way to see if the alternator is broken, it's a good way to break the alternator.

You said the engine is running so just connect a voltmeter to the battery and see what the charging voltage is. As long as it's above battery voltage at idle or 13-14 volts at a high idle it's good.

If the alternator isn't broken and you didn't manage to break it, leave it alone. Unless you have plans for adding a ton of electrical accessories, the original 10DN alternator will outlast any SI or any ten CS alternators.

True , thats a no no ,,, read this http://madelectrical.com/,,,

[mechanicalman]

If it turns out to be a bad voltage regulator, a new aftermarket solid state replacement is all you need.

If you wish to convert to internal regulator, all you need is this $21.00 kit.
27555 GM External regulator to GM “SI” series internal regulator
(This is an easy plug-in conversion that can be used with 1985 and earlier series alternators) . . . . . . . . 21.00 ea
http://www.americanautowire.com/cata...ersionKits.pdf

Unless you have some major accessories, you don't need more than a 63 amp alternator. If you go big, you may have issues with the gauge cluster. Vette Vet can steer you on that on how to do it right.

[GreenBay1921]

Okay, this is where I'm at. I've got 12.8v at the battery @ all times (running or not running). I've got 6 volts @ the blue wire of alt. & nothing @ white wire at any time.

[GreenBay1921]

I should probably add something. I don't have keys to the ignition, so I'm hot wiring it at the ignition harness. I supply 12v to the Pink wire & 12v to the Purple to start it. Is there something else I need to do here?

[VetteVet]

Originally Posted by GreenBay1921

I should probably add something. I don't have keys to the ignition, so I'm hot wiring it at the ignition harness. I supply 12v to the Pink wire & 12v to the Purple to start it. Is there something else I need to do here?

I don't know if i'm understanding you right but it appears that you are just hot wiring the ignition coil and the starter wire. You have to apply 12 volts to the brown wire that goes to the external regulator plug so that it can energize the alternator.

The normal way this is done is by way of a resistance wire from the key switch to the inside of the cab firewall block, where it is connected to the brown wire on the engine side of the firewall block. This resistance wire is 10 ohms and is used with the gauge dashes. If you have a charging light, the light will supply the 10 ohms necessary to protect the diodes in the alternator. The fact that you have zero ohms on the brown wire indicates that the voltage regulator is bad, except that you probably don;t have 12 volts on the brown wire before it gets to the regulator, given what you have said in the quote. I would recommend that you get a new key switch or connector, or what ever you need to repair the ignition switch.

[franken]

Voltage when running should be higher, but you may want to make the ignition switch work. Run a 1/4" drill 3/4 in and the key is no longer needed. Get a new key set and cylinder from napa and move on.

[GreenBay1921]

Thanks again guys. I'll drill out the switch & go from there.

[GreenBay1921]

Drilled out the switch & all systems go. Now on to other issues... like why she won't stay running...