67-72 not charging...WHY?

[72freak]

One of our spare parts builds is givng us some trouble. Everything is hooked up correctly, all connections have been checked and cleaned but it wont charge.

New voltage regulator
New alternator

What else can I check or try?

[71meangreenc10]

Is it a guage cluster or does it have the gen light? If it has the light, see if it is working when you start it, if not, fix it and see what happens....

Smitty

[VetteVet]

Your question is way to vague and general for a quick answer.
What type alternator and regulator do you have and what type gauge panel?
If you have the stock alternator and regulator make sure they are both grounded to the engine and the radiator support.

[72freak]

Originally Posted by VetteVet

Your question is way to vague and general for a quick answer.
What type alternator and regulator do you have and what type gauge panel?
If you have the stock alternator and regulator make sure they are both grounded to the engine and the radiator support.

Its a 3 gauge. Voltage regulator and alternator are whatever the parts store called for. They are all grounded and we have also attached extra ground jumpers for testing purposes with no luck.

The light on the gauge cluster is NOT coming on and I should have posted that fact with my original question. For my information DOES THE INSTRUMENT PANEL NEED TO BE PLUGGED IN FOR THE CHARGING SYSTEM TO WORK? I would not think so but who knows??

We are going to spend some time with it again tomorrow so any test tricks you may have let us know.

Again.....nice clean un-butchered harnes, new alternator, new voltage regulator, everything grounded, everything is hooked up corectly (99% sure)
but its not charging. Is there anything under the dash to check?

[VetteVet]

Well your statement that the charging light doesn't work and the fact that it's a three gauge panel helps a bunch. The alternator needs to see some resistance to charge the fields and to prevent the diode trio from burning out.
hopefully that hasn't already happened. It also needs the resistance to prevent feedback from the alternator circuit to the key switch ignition wire which would allow the engine to keep running when the key was turned off.

The bulb provides this resistance as well as a resistor wire from the key switch to the inside of the firewall block where it becomes the brown wire to the external voltage regulator. The three diagrams below will illustrate this.

This one shows the resistance wire and the bulb with the resistance wire as a back-up in case the bulb blows and the resistance wire also is needed for the seven gauge panel that has no charging light.



This one shows the brown resistance wire with the white stripe from the key switch. It's the fourth one down.



Follow it on this diagram and it leads to the firewall block and joins with a brown wire which goes back to the dash to the dash plug to the charging light. Refer back to the second diagram with the red arrows on the brown wire.



As you can see the brown wire feeds the light at pin 8 on the cluster plug and the bulb gets it's power from the pink wire on pin seven so YES IT NEEDS TO BE PLUGGED INTO THE CLUSTER. Also make sure that the cluster feed fuse in the fuse panel is good.The dash cluster also must be grounded to the cab.

[72freak]

Turns out the 2 wire plug that goes in the alternator was pinned wrong and we had power going to the srong side of the alternator. I am not sure if there is a difference during the 67-72 years...but that was it. We swapped the wires and al all is good.

[elf w/capital T]

Good to know, thanks and congrats on your troubleshooting adventure
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[ebry710]

I am running the same problem. My O' Railey's Alternator has been bench tested to work, but does not work on my 71' C-20. Are there alternators that have the wires switched? I am going to switch mine now.

[ebry710]

I love this forum. I flipped the wires, it didn't help. What I did do is reconnect the brown wire and that made all the difference. The manufacturer of the alternator said the brown wire was for the light and was optional. Since I was converting my unit over from 3 gauge to a 7 gauge cluster I figure I didn't need it. Two days later and 5 minutes on this thread made that a stupid idea.

I have to admit I have the cleanest wiring system on the plant. You'd be surprised how much crap people add to wiring so that could have a fancy radio, sun gauges and side/cab lights. I couldn't figure out why my lighter didn't work. What a mess. My stupidity had it's benefits and I know my wiring now....well at least better then I did.

Thank you for your help.

Wait, only my speedometer is hooked up to my new cluster, where does the brown wire go? I did notice a socket hanging by the steering column. Is that the socket for the light? Does it need a bulb?

[VetteVet]

This diagram shows it pretty clearly. The red arrows point out the brown/white resistance wire that originates at the key switch joined with the brown acc wire to the fuse panel for panel power. The brown/white 24 gauge wire runs to the inside of the firewall block where it joins an 18 gauge brown wire from the gauge cluster from the alternator charging light. Each of these wires provides 10 ohms of resistance to the alternator regulator to excite the alternator fields. Thus you can see why the alternator will charge without the gauge cluster being plugged in provided that you plug the brown wire into the alternator. This diagram shows the wire that plugs into the alternator as a brown/white 18 gauge wire yet it only says brown at the bulkhead.

[mac]

Great job VetteVet. My experiance is, no alternator field if the gauge panel fuse is blown. The circuit uses the panel lite filiments to drop alternator field voltage from battery level to @ 9.6vdc. Cost me an alternator to learn that lesson.

[ebry710]

If the charge light filament is the regulator for the regulator, what can I do to replace the light?

All that has been said is true.
- My 7 gauge cluster doesn't have the charging light.
- My old 3 gauge is on pieces and I do not have plans to use it again.
- The wiring harness for the two clusters are different.
- The charging light for the 3 gauge cluster is modular and cannot be adapted to the 7 gauge cluster.
- Currently, the resonance sound coming from my regulator is sounds an alternator with a bad bearing and the sound varies with engine speed.
- My alternator is running at a continuous 14.5 volts.

Obvious I have to re-examine my cluster upgrade, but I cannot use my truck with an with an over-amp'd alternator. I do not plan to use the stock gauges, just the stock design with after market gauges.

[fixit-p]

The charge light filament is not the regulator for the regulator, besides being a visual indicator of system performance it provides needed resistance in the field circuit. If you don't have a light you can use a resistor. Contrary to some opinions the resistance is not needed to step down voltage for the field (depending on what alt you have the field once excited gets its current directly from the stator winding's). It is there to limit current output from the field terminal thus protecting the diode trio or regulator depending on what type of alt you have.

The diagram below is of a 10SI alt (same for a 12SI) and it shows the diode trio connected directly to the stator, the diode trio is then directly connected to the field terminal. Which we can then conclude that the regulator and field winding's can not only handle full alternator voltage but is designed to do so.



The next image is a test connection of a carbon pile across the battery to test the alternators output. Notice the resistor in the #1 field terminal. If you were to load the battery with the carbon pile the voltage would drop, the sense wire would ramp up the alternator and produce the needed current to maintain voltage at the positive battery post. Without that resistor the alternator is going to push out current through 2 paths 1, the batt terminal on the alt and 2, the field terminal on the alt which is fed through the diode trio (which typically is rated @ 3 amps) shorting out the diode trio in the process. But with the resistor in place the diode trio is protected because resistance limits current flow. The bulb and resistors are also effective in preventing engine run on but the #1 goal of the engineers was to protect the alternator from itself.

[ebry710]

Originally Posted by VetteVet

Well your statement that the charging light doesn't work and the fact that it's a three gauge panel helps a bunch. The alternator needs to see some resistance to charge the fields and to prevent the diode trio from burning out.
hopefully that hasn't already happened. It also needs the resistance to prevent feedback from the alternator circuit to the key switch ignition wire which would allow the engine to keep running when the key was turned off.

The bulb provides this resistance as well as a resistor wire from the key switch to the inside of the firewall block where it becomes the brown wire to the external voltage regulator. The three diagrams below will illustrate this.

This one shows the resistance wire and the bulb with the resistance wire as a back-up in case the bulb blows and the resistance wire also is needed for the seven gauge panel that has no charging light.

Attachment 785738
.

Do this mean that the gen light doesn't go to ground, it just is place in the circuit between the ignition switch and the fourth leg of the regulator.

[fixit-p]

The gen light does not go directly to ground (it would stay on all the time).

It does however when wired in series with the field wire ground out through the field circuit including the ignition side depending on alternator output and battery charge.

[VetteVet]

WARNING LAMP
This is hard to understand but the light does not have a direct path to ground. In other words the light socket is not grounded to the cluster but it has two positive feeds. One comes from the battery via the pink wire from the ignition switch and the other is from the alternator also to the pink wire to the cluster then to the light via the same pink wire but the positive source is different. The brown white wire from the light is the feed path back to the alternator and also the ground path for the light as explained below and by fixit -p.


The alternator warning lamp. As can be seen from figure 5, a schematic for an actual alternator, there is a path to ground from the field current supply input [1] to the regulator. As a result, when the key is turned on, current flows through the warning lamp, through the resisters, transistors, and field coil, and then to ground, causing the lamp to illuminate. Once the alternator is at full output, voltage from the diode trio, also applied to [1], equals the battery voltage. At this time, with 12 volts on both sides, the lamp is out.



If the alternator should fail, voltage from the diode trio would drop, and once again the lamp would light from the battery voltage. If the alternator output is only a little low, the lamp will be dimly lit. If the alternator fails completely, and the output voltage goes to zero, the lamp will be lit at full brilliance. Conversely, if the battery should fail, and the battery voltage drops, with the output voltage of the alternator on one side and the low battery voltage on the other, the lamp will also light.

As stated earlier, if the light grows dimmer as the engine is revved up, it is because the alternator voltage is rising with the RPM, producing more voltage on the alternator side of the lamp. The closer the output voltage gets to the battery voltage, the dimmer the bulb becomes. By the same way, if the light gets brighter with increasing RPM, it is because as the alternator voltage increases, it is getting higher than the battery voltage. The higher the voltage with respect to the battery voltage, the greater the voltage difference across the lamp, and the brighter it gets.

If you look at the diagram I posted In my last post it shows the wires going to the light and the return paths to the ignition switch and to the alternator.

DISCLAIMER: I believe that this is the way it works so if I am wrong then some one please correct me. VV

[ebry710]

I think I understand. What I did was take a side marker socket and splice it in to the cluster harness at the brown and pink wires.

I started it up and the light went out. Tomorrow I'll put a meter on it, then drive it around. The wine is still coming out of my regulator, so it will go back to O'Reillys for a trade.

[VetteVet]

Your side marker light is a good idea to by pass the light in the cluster or to have a charge light in a gauge cluster but I don't see how it comes on unless the brown wire has a path to ground. You statement that the brown wire is coming out of the regulator seems to me that it is open from there and goes nowhere and it should go to terminal "F" on the alternator or to the no.1 terminal on the internally regulated alternator. On the external regulator the brown wire becomes a blue wire when it leaves the regulator and the sensing wire is white and connects to the "R" terminal on the alternator.

You must have a path to ground in the brown wire if the light is on when you turn on the key and if the light goes out then the path goes away after the alternator starts charging. If the regulator is bad then that might explain it.

[fixit-p]

Originally Posted by ebry710

I think I understand. What I did was take a side marker socket and splice it in to the cluster harness at the brown and pink wires.

I started it up and the light went out. Tomorrow I'll put a meter on it, then drive it around. The wine is still coming out of my regulator, so it will go back to O'Reillys for a trade.

The cluster plug you show is for a 3 gauge cluster the 7 gauge will look like the one below.

Also instead of using a marker light you could use the temp light in the 7 gauge cluster since it is not being used but it is still there all you have to do is re-pin the brown wire as shown in the pic below and islall a light in the cluster at the temp location.

[ebry710]

Replaced the regulator and checked the system. The side marker bypass worked well.

When the ignition is on and the engine is either off or at low idle, the light is on. As the rpms slightly increase to fast idle, the light dims and goes off. Perfect.

I really appreciate all the help you guys gave me. I hope other might get something out of this thread also.

O'Reilly's is probably not as happy as I am. The bearings of my original alternator when out so I replaced the alternator with a O'Reillys Ultimate Alternator, which immediately burned out my original regulator and one of theirs. I had them replace the bad alternator and the burnt out regulator. That second regulator screeched like a bad bearing (not bad since there are not bearings in a regulator). The third regulator is working like a charm..............but because of this bad luck, I understand my system and have cleaned up my electrical system.

[ebry710]

Originally Posted by fixit-p

The cluster plug you show is for a 3 gauge cluster the 7 gauge will look like the one below.

Also instead of using a marker light you could use the temp light in the 7 gauge cluster since it is not being used but it is still there all you have to do is re-pin the brown wire as shown in the pic below and islall a light in the cluster at the temp location.

I appreciate this input. With my truck finally operating again I can now continue with the transition from a 3 gauge system to the 7 gauge system. Re-pinning is now the next order of business.