Charging Problems. HELP!

[ATX Custom Delux]

Truck: 1971 Chevy C10 w/ 5.7 350sb.

Timeline:
Starter failed and battery was old/low. Installed brand-new starter and battery.

Alternator removed and tested in-house at Advance Auto. Alternator Test came up GOOD. Installed all components back into truck.

Tested at O'Reilly and Auto Zone..both said battery and starter good (as they are new) but Voltage Regulator FAILED.

Purchased new external voltage regulator and installed in vehicle.

System re-tested at Advance Auto and AutoZone and AGAIN shows voltage regulator FAIL.

Current Readings via Multimeter:
Battery before start" 12.7 volts
Battery when idle: 13.6 volts
Battery with all accessories on: 12.6 volts.

Any help will be greatly appreciated as I have no idea how to proceed. Thanks in advance!

[VetteVet]

Originally Posted by ATX Custom Delux

Truck: 1971 Chevy C10 w/ 5.7 350sb.

Timeline:
Starter failed and battery was old/low. Installed brand-new starter and battery.

Alternator removed and tested in-house at Advance Auto. Alternator Test came up GOOD. Installed all components back into truck.

Tested at O'Reilly and Auto Zone..both said battery and starter good (as they are new) but Voltage Regulator FAILED.

Purchased new external voltage regulator and installed in vehicle.

System re-tested at Advance Auto and AutoZone and AGAIN shows voltage regulator FAIL.

Current Readings via Multimeter:
Battery before start" 12.7 volts
Battery when idle: 13.6 volts
Battery with all accessories on: 12.6 volts.

Any help will be greatly appreciated as I have no idea how to proceed. Thanks in advance!

Here's how to proceed.

1. Make sure the regulator is grounded and the alternator is grounded.
There should be a ground wire connecting the regulator body with the alternator body but if they are both grounded that wire may not be needed.

2. Check the brown wire on the regulator plug for 12 volts with the key on and zero volts with the key off.

3. Check the red wire on the regulator plug for 12 volts with the key on or off.

4. Pull the small plug on the back of the alternator and check the white wire for 12 volts with the key on and zero with the key off. You can do this first but if you don't get the readings you'll have to do the other checks anyway.

Here is the circuit for the external regulator and alternator.

[ATX Custom Delux]

Thanks VetteVet!

Here are the results:

1. Make sure the regulator is grounded and the alternator is grounded.
There should be a ground wire connecting the regulator body with the alternator body but if they are both grounded that wire may not be needed.

All grounded, including a ground from alternator to regulator

2. Check the brown wire on the regulator plug for 12 volts with the key on and zero volts with the key off.

11.8 volts when keyed on. 0 volts when off.

3. Check the red wire on the regulator plug for 12 volts with the key on or off.

12 Volts read on red wire...keyed off and on.

4. Pull the small plug on the back of the alternator and check the white wire for 12 volts with the key on and zero with the key off. You can do this first but if you don't get the readings you'll have to do the other checks anyway.

No voltage read from white wire at alt plug with key on or off.


Now what? I am clueless when it comes to the wiring of these trucks.

Thanks again for the help!

[Wrenchbender Ret]

Bat. with engine at idle. 13.6. What is it if you rev the engine up a bit. This actually sounds normal. What is the problem now? These tests should be made with the bat. fully charged.
George

[greywurm]

i was having a similiar problem that i was about to throw the towel in on and replace the wiring harness... turns out a previous owner spliced a new pigtail connector from the regular to alternator deeper inside the harness and had the blue and white wires mixed up, so it was burning out regulators before i could even get a read on voltage.

Funny thing... I swapped to a new motor and went serp belt setup with a 1 wire alt about a month after figuring it out.

Look at the attached diagram, open up the harness and double check that the wiring to the reg, alt, and between them is correct. Also, when closing up the harness, do yourself a favor and use actual harness tape, not electrical tape. I have really gooey wires thanks to probably the same PO.

[VetteVet]

No voltage on the white wire will definitely not allow the alternator to charge. You should also have 12 v0lts on the blue wire with the key on. This is the wire that senses the need for the alternator to charge and the voltage that the blue wire carries charges the alternator fields depending on how long the regulator points are closed.

You should verify the continuity of the white and blue wires from the regulator as stated. You can run a wire outside the harness to carry the voltage between them and you can also check for 12 volts on the white wire terminal at the regulator to check for a break, in the white wire, in the harness.

The best solution IMO is to convert to a 3 wire internally regulated alternator for more power output and more reliability.

From past experience if the blue and white wires are reversed, the alternator diode trio will generate enough power to the ignition system to cause the engine to continue to run after the key is shut off.

It is not uncommon to have more than one bad regulator out of the box new.

[mike16]

dont presume that your alternator is good just because they tested it. I have bought 4 alternators in a row, first and third one tested bad on the car, second one tested bad right off the shelf. forth on is in the car, its bad with one bad diod.

the origonal alternator on my 90 camry lasted.....341K miles befor it failed. the failure was caused by it shorting out after I pressure washed the engine. 4 alternators later all with a life time guarrentee from auto zone. And I cant get one that works.

[Davidf]

When I purchased my '71, the alternator was overcharging the battery to the point of boil over. I drove it home and first order of business was a new voltage regulator AND new regulator wire harness connector. Everything perfect since. What I am trying to say is that the contacts at the regulator wiring connector can be corroded/burned to the point that poor or no electrical contact is made. Don't forget the simple stuff.

[ATX Custom Delux]

Thanks all for the advice! I have tested the blue and white wires for continuity and both seem solid ( from alt harness to regulator harness ). Again, i have 12 volts at the blue wire (alt) but nothing at the white when keyed on. If I have good continuity, I'm at a loss for what could be going wrong.

I've also tested volt output on the BAT terminal when car is running and reads a solid 14.2 volts at idle. Again, when all accessories are turned on, this reading drops down to the 12.4 range.

Furthermore, if I unplug the regulator completely, I get a low (12.4 volts) reading at the alternator, which leads me to believe the regulator is working in SOME capacity.

It seems as long as I am on the throttle, I am ok (per the batter indicator on my instrument cluster). I suppose I should just monitor the D/C indicator and turn **** off when I'm sitting at a red light?

[VetteVet]

Originally Posted by ATX Custom Delux

Thanks all for the advice! I have tested the blue and white wires for continuity and both seem solid ( from alt harness to regulator harness ). Again, i have 12 volts at the blue wire (alt) but nothing at the white when keyed on. If I have good continuity, I'm at a loss for what could be going wrong.

The exciter coil inside the regulator may be out of adjustment and not closing with key on voltage but when the alternator spins up it may generate enough voltage to close the exciter points and put power on the white wire. At idle it is normal for the alternator to deliver less than 14 volts until the engine is revved slightly. I know you are wondering, but he said the alternator wouldn't charge unless the white wire had 12 volts on it. That is correct however there can be some residual magnetism on the alternator fields that will be enough to start the charging cycle.

Another thing we don't know is what type alternator you have and how it is wired. Given what you have told us your alternator should look like this.

I've also tested volt output on the BAT terminal when car is running and reads a solid 14.2 volts at idle. Again, when all accessories are turned on, this reading drops down to the 12.4 range.

It sounds to me like you just need to upgrade to 12SI internally regulated alternator that can deliver 60 to 100 amps.

Furthermore, if I unplug the regulator completely, I get a low (12.4 volts) reading at the alternator, which leads me to believe the regulator is working in SOME capacity.

You're just reading battery voltage, nothing else.
It seems as long as I am on the throttle, I am ok (per the batter indicator on my instrument cluster). I suppose I should just monitor the D/C indicator and turn **** off when I'm sitting at a red light?

Bigger alternator.

[ATX Custom Delux]

Vette. That's the one. What do you suggest I ask for at the auto store? Alt for which vehicle?

[Wrenchbender Ret]

A smaller pully on the alt. might help. The idle speed may be slow. Some of those externally regulated alts. were only 42 amp. Rebuilders usually build them up to 55 amp. The original amp is stamped on the drive end housing.

[VetteVet]

Any 12 SI alternator usually mid 80s.

Here's one complete with conversion wiring.



Here's one just the alternator.





here's how I do It.



Get the plug-in from autozone or any of the stores.
Run the brown wire from the external regulator to the plug-in wire to no. 1 terminal.

Run the red wire from the external regulator to the no. 2 terminal wire in the plug-in.

[ATX Custom Delux]

Thanks so much. Definitely going to do this. Last question....what to do with the blue and white wires from regulator harness? Jump them? Shunt them? Or do they become irrelevant in this set up?

[VetteVet]

Originally Posted by ATX Custom Delux

Thanks so much. Definitely going to do this. Last question....what to do with the blue and white wires from regulator harness? Jump them? Shunt them? Or do they become irrelevant in this set up?

Well the white wire is just an extension of the brown wire and the blue wire is just an extension of the red wire. If the brown and red wires will reach the alternator then you don't need the other two.

If you decide to install a later model CS style alternator from the 90s all you have to do is wire in a 75 ohm 3 watt resistor in series in the brown wire and connect it to the L terminal on the CS alternator and connect the red wire to the S terminal on the alternator. most any resistor from 35 ohms and 5 watts to 300 ohms and .5 watts will work.

Some of the 94 and later alternators will only have the I brown wire going to the alternator.

[ATX Custom Delux]

VetteVet...a godsend. Thank you sir!

From other research, I've found that I should ask the auto store for an alt fitting a 1985 Buick Cutlass Supreme 5.0L. This will be a 12SI, 9 o'clock, 78amp alternator......AC-DELCO #321-244. Sound about right?

[VetteVet]

Originally Posted by ATX Custom Delux

VetteVet...a godsend. Thank you sir!

From other research, I've found that I should ask the auto store for an alt fitting a 1985 Buick Cutlass Supreme 5.0L. This will be a 12SI, 9 o'clock, 78amp alternator......AC-DELCO #321-244. Sound about right?

It should work. I can't guarantee the clock position because it's dependent on the alternator mounting and where the plug in needs to be. It's easy to re-clock if you're careful not to pull the alternator too far apart so that the brushes come off the rotor.

There are quite a few sources for the 12 SI and even more for the CS style.
The 87 S-10 trucks use the SI or so I've read.

Here's a favorite thread of mine for the members.

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

[ATX Custom Delux]

Vette, et al.
Thanks again for the information and installation advice. To follow-up, I purchased a 94 AMP alternator, ToughOne# P7292-9, and installed this weekend per the wiring instructions. Everything works great now and charging system is doing its job! Thanks again.

[ak808]

Not to take away from anything previous, but I did the 10si on mine but the stock two wire plug was no good. Where is a good place to find a replacement? Dealer only? Somewhere online?

Thanks!