alternator not charging

[cjoenny89]

Ok This truck has sat for 20 plus years and now that we are getting close to running it I see that the alternator isn't charging the battery or the gauge is bad. I did see that it has a voltage regulator mounted on the core support which threw me for a loop. I didn't expect to see a voltage regulator on a truck with an alternator. I know on my old tractors that use generators and voltage regulators that when you hook up a new battery or replace a part in the system it might require you to jumper the voltage regulator to tell it to start charging. Is this the case on this 68 Truck? do I need to introduce a spark somewhere to get the system live again or is something bad? what can I check or do to figure out why the alternator isn't showing a charge on the gauge?
Thanks!
Chad

[VetteVet]

You need a multimeter to make these checks.
Pull the plug off the back of the alternator and locate the white and blue wires in the plug.

With the key off, check for zero volts on the white wire and 12 volts on the blue wire.

Turn the key on and check for 12 volts on both wires.

Also check for 12 volts on the large red wire on the back of the alternator with the key in both positions. If you get these readings then most likely the alternator is bad. If you don't get these readings then the regulator is suspect or it's a wiring problem.

Pull the plug on the regulator and locate the brown and red wires.
Check the brown wire for 12 volts with the key on and zero volts with the key off.
Check for 12 volts on the red wire with the key in both positions.

If you get these readings then most likely the regulator is bad or the points are stuck
inside the regulator from sitting for so long, or you might have a wiring problem.

Do you have a charging light dash or a gauge dash?

[chiefcfd]

OK first an alternator has a voltage regulator. There are 2 types the external regulator mounted on the core support and an internal regulator inside the alternator. These trucks all had external regulators from the factory. Unless it has been changed you will need the regulator. First check all the connections and grounds. If that checks out have the alternator checked for charging. If you can drive it to a shop they can possibly check the entire charging system on the vehicle. IIRC the jumper wire you refer to on tractors were positive ground systems. That was a long time ago. I could be wrong. Hope this helps.

[hamjet]

Run a volt meter across the battery with engine not running, should be around 12 volts. start it up and check battery voltage again. if charging, you will see an increase in voltage, maybe 13+ volts. the gauge needle may just be stuck like mine.

[cooperhw]

Good info.

[cjoenny89]

I will take my Multi-Meter home from work I wasn't thinking of a stuck needle on my gauge. I will check the battery voltage before and after. I am sure it is wired correctly.
If I am not mistaken I have on my old tractors cleaned the points and had them start working but don't recall if this is a sealed unit. I will start with the battery test then go from there. By the way I have a needle gauge I don't recall if it is reading amps or voltage I just know it doesn't move lol! Thanks guys! Oh and by the way this truck was never switched over it is the old style alternator.

[swamp rat]

P.S...... Do not introduce a spark anywhere on an alternator even if externally regulated, thats strictly for the old generator systems.

[cjoenny89]

Ok thanks

[cjoenny89]

I can get the alternator to charge if I close the points by hand. I removed the cover and the regulator isn't pulling in the points. If I close them manually the alternator charges the battery and the gauge moves and at idle it puts out about 13 volts. Is there anything I can do or just buy a new voltage regulator?
Thanks

[VetteVet]

Do the checks in post 2 and make sure the regulator is grounded good and that it's grounded to the alternator.

When you manually close the points you are just bypassing the regulator.

Don't buy a new regulator, get a new or good used SI alternator and convert the wiring, it's super easy. You'll have more amperage for the truck systems, the lights won't flicker and the truck will run better.

[cjoenny89]

thanks I will do the test!

[Devins-step]

I agree with Vet. switch to a modern altenator with internal regulator. easy switch and at least twice the amps out put.

[hwyix]

Originally Posted by Devins-step

I agree with Vet. switch to a modern altenator with internal regulator. easy switch and at least twice the amps out put.

^^^^^^ this.


The others had great advice on testing which is good info. At sometime I highly recommending switching to modern alternator.

[mike16]

start the truck up and place a small screw driver on the back bearing of the alternator.if you feel a light magnetic pull; the alternator is working. it may have a bad diode and that can be confirmed with a multimeter. alternator and regulator servicing is spelled out pretty good in the service manual.

Sometimes on those old electrical systems that have external voltage regulators. the points or other mechanical mechanisms with in the voltage regulator can be rusted to a point where they do not function. pull the cover off and if thats what you see , simply replace the voltage regulator. mine os origonal to my truck, 72-c10, and still works great but I've seen rusted and burnt ones that no longer work. Dont bother recutting the points. No body even sells point files anymore. the Chicom files actualy leave metal on the surface of the points and can cause them to burn again quickly and corrode because of dissimilar metal corrosion.

the new regulators ar electronic and the old delco remy cover screws right on.

[cjoenny89]

Thanks for the help! I found the ground wires off the front cowl and regulator when they painted the stuff they didn't wire it back up and the ground wires were tucked down inside where you couldn't see them. It charges just about 14 volts when the truck is running. Either it stopped working last night or it doesn't show any charge unless it needs it am I correct? The gauge will not move up if the battery is at full charge?

[Harley03joe]

Question: ?
Does The Red Wire On The Voltage Regulator Go The The Positive Connection
On The Right Side Fender Connection Where The Positive Wire Goes ?
And Does That Little Fuse Link Go There Also ?
On My 1971 C 20
Thank You For Any Help Or Pictures
Harley03joe