Need Help! Alternator problem/charging issue

[boynton]

Ok so I have a 1970 c10 with a 350-hei internally regulated Alternator. I can jump it off and it runs until I shut it off. Thought tge battery was weak so I changed it. That did not work. I thought maybe I didn't have a good connection back to the battery-wired through the starter, so I added a wire directly to the battery, still having issues. I then thought maybe the alternator was wired wrong-the wire to the ignition, so I ran a new wire to the ignition. Still n o result. I then thought maybe the alternator was weak, so I changed it, still no difference. Any ideas?

[Green Hornet]

That is a very simple alt to wire. Large post goes directly to the battery. From the large post make up a jumper wire to go to one of the two prongs on the connector. The other prong gets switched power. you should be putting out about 14.5 volts.

[68gmsee]

Need a little more info. You say it will start fine if you "jump it off" -I'm assuming jumper cables to battery posts -and you replaced the battery and alternator. If the battery has a full charge it should start the engine without jumpering.

If it's draining off while running, the alternator is either wired wrong or it's still bad. If that's the case, check the voltage from plus to negative battery posts with a voltmeter while it's running. It should be anywhere between 13.5 to 15 vdc. If it's not, check your wiring again and put a good charge on the battery to see if it will start the engine without jumpering (eliminates it being bad).

[68gmsee]

Check with this wiring diagram.

[boynton]

Originally Posted by 68gmsee

Need a little more info. You say it will start fine if you "jump it off" -I'm assuming jumper cables to battery posts -and you replaced the battery and alternator. If the battery has a full charge it should start the engine without jumpering.

If it's draining off while running, the alternator is either wired wrong or it's still bad. If that's the case, check the voltage from plus to negative battery posts with a voltmeter while it's running. It should be anywhere between 13.5 to 15 vdc. If it's not, check your wiring again and put a good charge on the battery to see if it will start the engine without jumpering (eliminates it being bad).

It won't die while running but I can jump it as described runs fine, then I shut it off and it won't start up. Tried three batterys to this point so I know it isn't the battery. I'm going to try completely rewiring the alternator and see what happens. I don't know what else to do.

[68gmsee]

Originally Posted by boynton

It won't die while running but I can jump it as described runs fine, then I shut it off and it won't start up. Tried three batterys to this point so I know it isn't the battery. I'm going to try completely rewiring the alternator and see what happens. I don't know what else to do.

I have a 350 engine sitting on an engine stand and it would crank fine with a bad alternator. I did have a fully charged battery, though.

Seems to me that if you have tried three fully charged batteries and it won't even crank except by jumpering there's something definitely not right. Don't know what, but it should at least turn the engine over. Remember, all you're doing by jumpering is bypassing a weak battery that's not fully charged. Got to be some really bad connection somewhere.

[boynton]

Originally Posted by 68gmsee

I have a 350 engine sitting on an engine stand and it would crank fine with a bad alternator. I did have a fully charged battery, though.

Seems to me that if you have tried three fully charged batteries and it won't even crank except by jumpering there's something definitely not right. Don't know what, but it should at least turn the engine over. Remember, all you're doing by jumpering is bypassing a weak battery that's not fully charged. Got to be some really bad connection somewhere.

It will start fine without a jump with a good battery but it drains after a few runs. I'm convinced there is a wiring issue. I'm going to try running all new wire that has anything to do with the alternator and see what happens.

[Lee H]

Have you load tested the battery?

[am0254338]

So with jumpers it always starts right up?...If it was me i would go get a one wire alternator and try that. That would eliminate most wiring issues, but that's just me. Def sounds like a alternator issue.

[MARKDTN]

Originally Posted by am0254338

...If it was me i would go get a one wire alternator and try that.....

1-wire alternators are not the best for a street application. They are best suited for machinery and other low amperage applications. Because of the 1-wire configuration you lose the ability to sense load and they don't recover as fast as a 3 wire configuration.

[Green Hornet]

When you jump it are you hooking the negative jumper on the dead truck to the battery or the engine as a ground? if your hooking it to the engine you may have a bad ground to the block.

[davepl]

I can't promise this won't hurt anything, but if you unplug the alternator while the truck is running, does the idle speed up, like a load has been taken off? And is the alternator hot?

Often, if a diode pack goes, it will be basically a short circuit inside the alternator.

Your description though makes it sound like it will never restart unless you're boosting it, regardless of the state of the battery. If that's the case, if there were some safe way of boosting it with the cables hooked right to the battery, and if it then didn't crank, you'd know it was a connectivity issue with your battery cables.

Since I'm going to guess you're hooking up the negative booster cable to the engine, I'm going to wager that you have a bad ground between the engine and the frame/battery.

To test this theory, just use the black cord of the jumper cables to connect your (charged) battery's negative post to a good ground on the engine. If that fixes it, you've found your problem and need to fix the ground.

[airdale94]

It sounds like your starter is drawing to much current.

[boynton]

Originally Posted by airdale94

It sounds like your starter is drawing to much current.

What would cause my starter to draw too much current and how do I correct it?

[airdale94]

A defective starter will draw to much current. They can weaken a battery. A shorted alternator can drain the battery and still charge.

[boynton]

well it turns out the wire going to the starter had melted against the manifold. honestly i am lucky it didnt catch fire. disaster missed and charging correctly now. I drove it all week with no issues and it cranks right up