Alternator wont charge battery

[Coalkracker]

On my 70 c10 I have an externally regulated alternator that is not charging my battery. New alternator and new regulator. With the key on I have voltage at the brown wire and red wire at the regulator harness. When i plug the harness into the regulator and turn the key to on position i have no voltage at the white and blue wire at the alternator plug. Am I checking this correctly and where do i go from here to test further?

[Rick Bollinger]

I belive your black wire should be ground. And check your fusible link at your battery to your junction block. Here is a link should help. I went with a new one wire alt and its great.
http://67-72chevytrucks.com/gallery/...&size=big&cat=

[Coalkracker]

Black wire is grounded and fusible link has continuity.

[Coalkracker]

Maybe my alternator is bad.

['68OrangeSunshine]

If you got your Alternator and EVR as warranty-exchanges from a large auto parts chain, there's a possibility that they gave you defective parts. Have a rival chain do a diagnostic check on your truck's system for a second opinion. Then go back to the chainstore you got it from and demand they get you good parts.
This has happened to me with the Alt and EVR on my '68 C/10 Stepside.

[Coalkracker]

They werent warranty exchange. Bought them from seperate stores also. Are the blue and white wires supposed to have power with key turned to the on position? Im just trying to narrow it down so i know what to buy to fix it.

[Coalkracker]

Is the regulator supposed to be n/o or n/c?

[WorkinLonghorn]

This is a known good battery and with the engine running you have only ~12v at the battery terminals?

[Coalkracker]

The voltage i get depends on how many starts i have on the battery since i charged it last. Also when i test the battery terminal on the alternator im just getting the same voltage as the battery. If i have for example 11.8 volts on my battery before i start my truck it may bump the voltage down to 11.6 volts from using the starter. Then while it is running i can test the battery and still only get 11.6. Then i test the battery post on the alternator to ground and i get the same reading there.

[Coalkracker]

Since when i test the alternator to ground with the truck running and only get the battery voltage instead of the higher charging voltage does that mean the alternator is indeed bad and i can rule out the voltage regulator?

[Steeveedee]

Can't find the link, but a member uploaded a bunch of the factory service manuals. They tell you how to troubleshoot and fix just about everything. Look around for it and get the one you need.

[Coley]

...sounds like a job for VetteVet

He's somewhat of an electrical guru who can help you get this sorted out.....and it doesn't sound like it should be too difficult to get to the bottom of things.

Coley

[RichardJ]

>>When i plug the harness into the regulator and turn the key to on position i have no voltage at the white and blue wire at the alternator plug.<<

For starters, don't unplug anything when testing.

Your "brown" wire should be the wire from the ignition switch and should connect to #4 on the Reg plug. It should be hot with the "key" ON.
#4 should connect through the regulator Voltage Relay to the "F" terminal of the Reg plug and have the same voltage.
The "F" terminal of the Reg should connect to the "F" terminal on the Alt. It may be a Blue wire, but it's never a good idea to trace wires by the color of the insulation on 50 year old wire harnesses.

The wire from Alt terminal "R" to Reg terminal #2 will have enough voltage to close the Field relay, but only after it begins to charge.

The wiring diagram shows a lamp and a resistor connected at the ignition switch. You won't have the lamp if you have a Ammeter gauge, but you will have the resistance wire.

[Coalkracker]

Ok so im getting no voltage on the F terminal while running and just my battery voltage on the R terminal while running....

[Coalkracker]

But those voltages are if i test them to the BATT trrminal on the alternator...i get nothing when testing them to ground

[Coalkracker]

This is confusing the heck out of me because i dont even know where the coil is getting power from to make the engine run.

[Nestevec]

When you buy a new alternator sometimes during shipping they forget to take out the paperclip or drill bit that keep the brushes from moving. Had that issue with my Chevelle. Removed the drill bit that was left in there and it worked fine.

[Coalkracker]

I ended up changing the alternator with a new one and I am having the same problem. I've stated the results of my voltage testing, where do i go from here?

[WorkinLonghorn]

I'm pretty clueless with electrical stuff but did you clean the ground location and run the little ground strap for the regulator? Isn't there a resister there too that needs to be replaced (I can't remember)?

Also, I'm becoming pretty well versed with electrical dumb mistakes. Once I thought I had a problem but I wasn't completely inserting the regulator connection until it snapped all the way in.

And once I replaced the ignition switch and somehow the little brown and white wire that goes to the voltage regulator came loose. It shares the connection on the Ign. switch with the large brown wire. See this thread (but the picture doesn't show the wire as brown and white as it should).

http://67-72chevytrucks.com/vboard/s...d.php?t=469854

[Coalkracker]

I cleaned the grounds and tested to make sure and they all check out. I didnt run a ground strap but the regulator has a ground jumper coming from the core support thst connects to it. I didnt see a resistor anywhere there to replace. Theres a condensor that i didnt change but i dont think that would affect it. I think the condensor is just to prevent electrical noise in the radio but i could be wrong.

[Coalkracker]

Could the wire on the ignition switch possibly be my problem?? Im going to have to start checking everything i can now since its still not giving me a charge.

[HO455]

This thread may help.

http://67-72chevytrucks.com/vboard/s....php?p=7524043

[Coalkracker]

Does it make a difference if I put the ground wire on the ground terminsl on the alternator versus the alternator bracket? I had it on the alternator but switched it to the bracket because i wasnt sure which one was better. Still didnt make a difference though. My ammeter doesnt seem to be working either. I changed the fuses and it still doesnt move from middle position. Not sure if thats a sign of something either.

[RichardJ]

Don't trouble shoot the ignition system if you are trouble shooting the charging system.

>>But those voltages are if i test them to the BATT trrminal on the alternator...i get nothing when testing them to ground<<

Take ALL voltage measurements FROM ground unless you are looking for something specific. For instance. Measure voltage from battery ground to the body/base of the voltage regulator. This is how you know if the voltage regulator is properly grounded and should no more than about a tenth of a volt.

You said,
>>Ok so im getting no voltage on the F terminal while running and just my battery voltage on the R terminal while running....<<

But, in your first post,
>> With the key on I have voltage at the brown wire and ..... turn the key to on position i have no voltage at the white and blue wire at the alternator plug.<<

The voltage you measure from ground to the #4 Reg terminal should be the same as the voltage from ground to Reg "F" terminal. This voltage should be the same as ground to Alt "F" terminal.
It isn't unheard off that someone could have switched the two wire terminals on the plug that plugs into the Alt. That is why I am asking to check voltage on the Reg "F" terminal and the Alt "F" terminal.

[Coalkracker]

Yes thats correct about what i said in my first post. I unplugged the connector and checked the plug, not knowing i wouldnt be getting any reading from there. The last time i tested i checked it from the splice i made when i added the new plug for the R and F wires. I will check as you said. The only thing im not sure of is how do i check them while the connectors are still plugged in?