So i took my truck out on the trails 2 times this past couple of weeks. Each time i was having charging problems.

Trip 1:The truck ran fine for about 45 minutes. It was idling and i was away from my truck for 10 minutes. When i got back it was dead. We jumped started it on the trail and after about 5 minutes of driving, my headlights started to dim. Another 5 minutes later the truck started to run like crap and eventually died. I came to the conclusion that it was the alternator. I parked it in the woods, jumped in a different truck and rode around for a bit. At the end of the night i got another jump start and was able to drive it home.

Last week: So i thought it was the alternator. So i replaced that with a brand new one. I didn't test it with a meter after i installed it, but instead i just pulled the positive terminal off while the truck was running. The truck stayed running while the terminal was off. So after thinking i had solved the problem i felt confident to take it out again.

Trip 2: The truck started right up after sitting for a couple of days.
As i was letting the truck warm up, i was grabbing stuff out of the car to load into the truck and i noticed how bright the lights were. When i got to our meeting place on the trails, we noticed our lights weren't as bright as when we left but the truck was running fine. We drove for about 45 minutes and my lights were getting dimmer and dimmer. After a while it was like i had a lit candle for headlights.The truck was still running great however. Eventually i stalled the truck out trying to climb a hill in 2 wheel drive when i should have been in four(my carb needs a cleaning badly). I knew the truck wouldn't start because it didn't have enough battery. So we jumped it and it fired up and ran fine but it stalled again shortly after. But this time it seemed like it just didn't have enough juice and died. So after being fed up my buddy gave me a good long jump and i drove the truck back home. When i parked the truck it was running fine. I did notice when i kicked the heater on that my lights dimmed a lot. But as soon as i shut the heater back off the lights lit back up. So i shut the truck off and tried to start it. But as i figured, it didn't have enough juice to start back up.

Today: So i am trying to figure this out and need some help(again). Is it a bad voltage regulator?? Could the battery (that i just replaced this past july) be bad from it dying and recharging it too much? Is the alternator not able to keep up charging the battery while i am using my lights and heater?? I just don't understand why the truck was running fine but i was still losing power. It's getting very discouraging thinking i have this thing figured out and having the same problems. Any help or thoughts would be greatly appreciated. Thanks.

 

I don't know a ton about electrical but I had a similar problem when I first bought my truck. My alternator tested fine, but the battery was toast so I swapped in a new battery. Everything was good for a couple days then I started having the same problems again. I went ahead and replaced the voltage regulator and haven't had a single proem since and it's been my daily driver for the last 6 months.

 

Yes, I think it is your voltage regulator, unless your new alternator is faulty.

If the battery was the problem your truck wouldn't die when left running.

No way to be certain though without testing, but if I was you I would replace the regulator.

 

Did you check your voltage before and after starting the motor ? Should be 12v before and about 14v after .

My bet would be the regulator too.

Do you have a good ground strap from the motor to the body ? If your + & - are good to the motor but you have a poor/rusty ground to the body(regulator) funny things happen .

 

Around 12.3-12.6 when the truck is off, 13.5-14.8 when running, but yeah, I'd agree with the reg.

 

thanks for the replies. i'm pry going to change the regulator then. Hopefully this will solve the problem. i will pry have the battery tested too. Also, will i need to buy a new plug in or would it be fine to use the old one??

 

This is never a good thing to do as it can fry the diodes in any alternator.

See: Alternator Field Disconnect

Are you doing any proper diagnosis and testing (using a meter) at all? It sounds to me like you're just throwing parts at it based on what you think the problem should be?

Do a google search on automotive charging system diagnostics, there's lots of good stuff out there.

 

Yeah, I have kind of been doing that. But most the parts needed replaced anyways. But my friend has a meter that I am going to borrow and check the truck out soon.

 

Well no better time than now to dump the factory charging system and swap on the 3G alternator.


With a multi-meter you will be able to troubleshoot alot better.

 

As Chris said, don't disconnect the alternator (or really any part of the charging system, including the battery) while the engine is running. You should ALWAYS, ALWAYS, ALWAYS!!! remove the negative battery cable before servicing any part of the charging system, and for that, the engine has to be off anyway. I CANNOT stress that enough. I am not simply regurgitating warning labels when I say this.

I agree that the voltage regulator is another likely culprit, unless the original alternator was the culprit and the new one is bad out of the box. However, it's not proven yet. There are some simple checks you can do with a multimeter to make sure the regulator is getting power in the first place. Does the truck have an ALT light or an ammeter in the dash? I also don't think it makes sense to throw parts and money at a truck without trying to understand the problem.

 

Yes there is an alternator light in the cluster. It came on during the first trip now that i think of it. And no i don't want to just throw more money into it without understanding the problem. That's why i posted here. I will test with a multimeter before buying new parts. The alternator i took off was bad though. I appreciate all the feedback.

 

Here are some basic checks to do:

1) Unplug the regulator and measure the voltage at the "I" terminal on the connector with the key in RUN. You should have 12 volts. If not, the regulator can't bring the alternator online. The "A" terminal on the connector should have 12 volts at all times.

2) You can do a quick check of the alternator by unplugging the regulator and starting the truck. If you jump the A terminal of the connector to the F terminal, you should hear the alternator wind up to go full charge and the output should jump. This should only be done very briefly.

3) Make sure the regulator is grounded properly. There should be minimal resistance between either regulator mounting bolt and the engine block.

You can also have the regulator tested at most parts stores on a bench. If you don't have the original regulator and are running an electronic replacement, this is the only way to test. The procedures listed in older shop manuals only apply to the original electromechanical style.

 

check your wires. could be corroded, causing high resistance and not allowing current to flow enough. we had to do this on a full size chebby blazer not that long ago. poor kid bought a new batter and alty and still didn't fix anything. turned out his positive wire from the battery (B+ wire) had burnt just right where the truck wouldn't charge. new B+ wire and he's never had a problem since.

your B+ wire shouldn't have more than 0.2ohms of resistance. an easy way to test the B+ wire is to take a volt meter, connect the + lead to the + post on the battery, and the - lead to the B+ post on the alty. you shouldn't get more than a 0.4v (had to crack open my diagnostics book for that one) drop across that wire. if that one is over that, it's junk. if it's good, test the negative side. you go from the alty case with the + lead and put the - lead on the negative battery post. if it's more than a 0.2v drop, you have a grounding issue.

 

Do I check the wires while the truck is running or off?? I went ahead and tried a new regulator and the battery I had, tested bad. I know I know, just throwing parts on, but the regulator was fairly cheap and I had a warranty on the battery. I was unable to get ahold of a meter. But took the truck out tonight and ran into the same problem. As long as I dont stall out i'm golden. But once the trucks off I'm stuck. I am fairly new at learning my way around a truck. Most the stuff I know, is stuff I've learned offline. So bear with me.

 

Also I wonder if I hooked the sylenoid up wrong. I had a bad starter a while ago that was shorting out my sylenoid. I had the starter rebuilt and bought a new sylenoid. Could I have put a wire in the wrong spot when hooking it back up??