Hot Rods Perplexing electrical issue, runs for a minute then completely dies...

Getting thorough...just dug into the fusebox...no breakers, just fuses. Everything looks good. Even though the alternator is charging, is it possible another internal abnormality could cause this? It's essentially a one-wire alt. I feel like a nag!

 

It's unlikely to be a fuse. Usually they just pop and parties over. And since u are losing so much power it would have to be a big amp fuse and if that was somehow still flowing juice I'm sure u would've had a fire by now. Try lettin the car run and start feeling wires and see if any are getting hot. That would imply a bad contact somewhere. And again since the whole car is dead I would focus on main powers and grounds. Check battery terminals too. Good luck

 

I know you said you already checked them, but i just went through pretty much the same thing with my Buick. Turned out to be a bad connection on the negative battery cable to the motor.

 

Rather than using the shotgun method of troubleshooting, let's think about the problem and plan a series of tests to locate the issue. First, the engine runs for xx minutes and then dies. It wont restart but will be OK if you wait a while. Hmmmm, that sounds like the electrical heat gremlins are possessing the system. IF ALL electrical stuff goes dead, it is NOT a single circuit, fuse, or breaker. Therefore, it must be in the primary battery/charging/cable area of the system. First, you gotta have a real volt meter. No radio shack crap, a real volt meter. Pretty much everyone has one, borrow one if you don't. All of this stuff is stuff that has been posted before but ignored. First, measure the voltage across the battery with the engine off (but ready to start). Touch the battery posts to measure the voltage. The voltage should be 12volts or more. Start the car and measure again after you have turned the alternator on (you do know that a powergen is a one wire alternator and has to be goosed to turn it on, don't you?). With the powergen on and the motor running, you should have MORE voltage than you did before you started the engine. Was it more? If not, the powergen is suspect but not necessarily the bad guy. If it was higher running, that is good.
Next, when the engine lays down and quits, measure the voltage across the battery again. What is it? Less than 12 v (or maybe 11.8 v) is bad, indicating a battery that has run down. However, it may not be the battery.....yet. Quickly before the system heals itself, try turning the lights on. You said they wouldn't even dimily illuminate when the system died. Next, quickly use jumper cables to connect another good battery to your battery. Don't start the car, just see if the headlights come on with the jumper. Did they? IF NO, you have a cable issue....a primary cable or cable ground that is too high resistance or making intermittent contact. Someone mentioned an internal break, that is a good possibility. IF the headlights came on, you have a battery problem or a powergen problem.

More later.

 

Dude...Disconnect the single wire from the alternator...use a jumper wire from that wire to the battery..thereby eliminating the alternator from the electrical circuit and I bet you you're problem will be gone. Cost? Zero. Time involved? 5 minutes.

 

Thanks for the replies! I just read these after a couple hours troubleshooting. I charged the battery, even though it had a resting voltage of 12.76. I checked the voltages at different spots:

-Battery- 12.76
-Starter solenoid- 12.76
-One-wire Powergen alternator- 12.76

Then I started the car and it idled for 7 minutes:
-Battery- steady at 12.76
-Starter solenoid- 12.76
-Alternator- between 10.7-12.2, sometimes fluctuating a little lower...tended lower as the car warmed up

I know most alternators charge at around 14.7, right? The alternator does feel quite warm/mildly hot. That sounded stupid, anyway...another thing, after I shut her down she wouldn't start and zero power to anything. I checked the battery, 12.76! I checked the alternator...over the course of the next hour, the voltage steadily dropped to 2.8. I'm watching to see if it goes back up. I'll try Black Panther's suggestion a little later. Keep you posted.

 

you have a bad wiring connection somewhere between the battery and the rest of the car. When you see 2.8 volts at the alternator, you need to start measuring from the battery, and see where the voltage is dropping.

the alternator output should be the same as the battery, within a tenth of a volt. But the drop could be on either the positive side, or on the ground (negative) side.

Go exploring with your voltmeter, see what you can find! pay attention to both leads on the volt meter, too.

 

Been following along here.

I have a guess,
it may be possible the alternator is internally shorting.
Bad diodes or rectifier .
I would disconnect the alternator and try running without it. Quick and easy.

On another note.
no one mentioned to check the ground strap
engine to frame
And
Engine to body.

 

Like Squirel said its a bad connection, have you checked the positive cable to the starter?

 

Somewhere a primary circuit warms up and parts? (opens)

 

All grounds checked, all shiny and clean. Engine to frame, battery to frame, positive at battery and starter. The alternator stuck at 5.8 volts then, all of the sudden, it sprung back to 12.76...just like the battery and everywhere else. It also seemed to cool down pretty quick. I think it's alternator-related, as hacknwhack suggests...some sort of internal short. Getting closer. Wiring is not my strong suit so forgive my ignorance...how do I bypass the alternator? Just disconnect it and start? I appreciate all the help, I feel like electrical is the only thing I haven't had to delve into with this car!

 

Read down here, about heat causing the 3-diode assy to drop out.
http://www.hotrodders.com/forum/gm-one-wire-alternator-problem-161128.html

 

Disconnect battery before working on alternator!

Aftere removing nut on alternator, tape off eyelet end to prevent any short circuts.
Reconnect battery then start engine.

I have some more test you can do if this doesnt solve it.

 

I have had a similar problem with 2 trucks. Culprit was a bad ammeter. If you don't have one I would look hard at your alternator, swap in a different one to test.

 

I keep thinking Ignition switch!!

 

While the car is running tug on the wiring harness in different locations while watching for the engine to stumble. This might get you closer to the problem without a lot of testing. It does sound like you have a poor elec connection showing itself when it heats up due to the resistance.

 

Alternator. Remove and have it tested. I had the very same thing happen in all respect's to your post. All my testing came to the same conclusions you have. Had the alternator tested and if was fried inside. Your battery is taking a beating from all that cycling up and down, not good for it.

 

I finally found the culprit...it was part of the battery wire between the solenoid and the alternator. With the meter hooked to the alt., I just started jiggling wires around and found a link that was loose in part of the wire that was hard to see/get to. I just replaced the whole wire, PROBLEM SOLVED!!! Seems to run smoother than before, volts at 13.2 at idle...all's well! I think my alternator was working overtime because of the issue, now it runs quieter and cooler! It's hard to believe a single wire could be such a headache. Thanks for all the help.

 

Hope you found the problem....but I don't know how that loose wire would exhibit symptoms like you listed before. How does a loose wire work better when it's cooled off? If your alternator was working harder than it should have because of the loose wire...maybe it got damaged?

 

Never under estimate the wiggle test . Just to add to the testing (since i'm late to the post) to check the connection from the battery to the battery cables, put the meter on the battery posts themselves and check voltage, then take one lead (doesn't matter which one as you will switch them to check both) and touch it to the battery cable. Then switch them to check the other cable, only do this when the power is completely gone.

 

This is essentially what fixed it(and garyf's "tug test"). Instead of running a jumper wire, I just replaced it.

What I think could have happened is a combination of things:
-The wire just got worse and worse with all the poking and prodding to the electrical system and started to cut everything under simple vibration.
-The alternator was working harder and less effectively trying to push charge to the battery through that wire, and a hot engine only exacerbated the issue. As the alt. got hotter, it started getting funky.

I did a bunch of driving last night, zero problems. Checked voltages, all great. All-in-all, it was annoying but a good learning experience...especially since I didn't have to buy a new $400 Powergen! Thanks again, everybody!

Adam

 

Adam....sounds like it worked out the cheapest way possible which is always a good thing...

 

Thanks for posting what you found. On single wire alternators, I like to run the wire from the alternator directly to the battery positive terminal with a maxi fuse or circuit breakers. The Powergen is rated at 75 amp so it requires at larger wire than the stock harness. If the battery is in the rear, you can connect to the starter terminal.

 

Exactly what I did! A second opinion is always good.

 

Congratulations. A few more experiences like that and you'll be as big a "voltage drop" enthusiast as me. Measurin' beats parts swappin' almost every time .

I'm unclear what the "link" is in your description "found a link that was loose in part of the wire that was hard to see".
Crimped connection, Bolted connection, plug connector, ???

 

There are few combination's of way's a primary feed can been made. I did not take this into account when I replied. After rereading OP's voltage at the 3 sources he tested I realized his primary feed may of came direct from the alternator to feed the fuse box and ign. switch. Which leads me to think he has 2 primary wire's at the alternator. 1 feed in (bat) and 1 supply out (charge) and they both burned away because the supply over heated and took out the supply running next to it ? Xadamx may clear this up for us.

 

Good Job!!!!