Charging issue?

2001 1500 5.9 V8

I notice quite a bit of dimming from all my lights when I'm driving at night.

If I drive without headlights on my volt meter pegs out in 10 minutes or so and causes the "check gauges" MIL to come on.

If my headlights AND a/c are on, the volt meter dumps to nothing and causes the same MIL to come on.

If just my lights are on it hangs around 14 volts.

It's got dual batteries with an isolator that were there from its forest service duties.

noticed the other day that the second battery wasn't hooked up. put a volt meter on it and it read like 1-2 volts. hooked it up with it running and tested it again and it only read 12 volts.

I suspect the isolator or the alternator is not doing it's job well.

Is there a good alternator upgrade out there?
There will be lots of accessories in the future and I would like some serious power output.

Thanks

I'm having the same no charge issue...
New alternator, 2 new batteries and still not charging...NEW HELP!

pwaite92 said:

2001 1500 5.9 V8

I notice quite a bit of dimming from all my lights when I'm driving at night.

If I drive without headlights on my volt meter pegs out in 10 minutes or so and causes the "check gauges" MIL to come on.

If my headlights AND a/c are on, the volt meter dumps to nothing and causes the same MIL to come on.

If just my lights are on it hangs around 14 volts.

It's got dual batteries with an isolator that were there from its forest service duties.

noticed the other day that the second battery wasn't hooked up. put a volt meter on it and it read like 1-2 volts. hooked it up with it running and tested it again and it only read 12 volts.

I suspect the isolator or the alternator is not doing it's job well.

Is there a good alternator upgrade out there?
There will be lots of accessories in the future and I would like some serious power output.

Thanks

Click to expand...

I can't speak for upgrades, but I would check all your connections for corrosion or looseness. If its all clean and tight, measure at the alternator for voltage, it should be above 13.2 volts with lights and a/c on. It can vary max voltage but mine likes to hover around 14.1v at night with headlights and fog. I would expect yours to be above 13.8v when its been running for more than a few minutes. If it just wont go above a problem voltage you may have an issue with the PCM, as that controls the charging rate. Short of testing the alternator outside the vehicle or replacing it I wouldn't immediately suspect the PCM. You could also check out the battery temp sensor and make sure its both hooked up and attached on the bottom of the battery tray. The PCM reads battery temperature to determine charge rate.
Without knowing what kind of isolator was being used I can comment on that at all. That 1-2 volt battery is junk, I wouldnt even try to charge it, it was nearly pure water if it was at 1-2 volts and the sulfation will be extreme.

99DodgeWham3500 said:

I'm having the same no charge issue...
New alternator, 2 new batteries and still not charging...NEW HELP!

Click to expand...

Check for corrosion or loose connections. If its clean and tight, test for voltage at the alternator, if its above 13.2v check at the batteries for the same voltage. If they are not within .2v you have a problem. These trucks have a battery temp sensor that is read by the PCM to control charging if you've got a new alternator and the voltage is the same at both the alternator and battery I would suspect a PCM issue as the voltage regulation is handled there. You are going to want to see if its throwing a code.

Havent been getting any codes although I havent actually checked while the problem is happening. I think what I will do is unhook the 2nd battery and isolator and run it like normal and see if that works until I am ready for a new dual setup.
What should my positive wire routing look like? Alternator straight to the fuse block, right? and then battery also to the fuse block? or does it need to run to the starter also?

pwaite92 said:

Havent been getting any codes although I havent actually checked while the problem is happening. I think what I will do is unhook the 2nd battery and isolator and run it like normal and see if that works until I am ready for a new dual setup.
What should my positive wire routing look like? Alternator straight to the fuse block, right? and then battery also to the fuse block? or does it need to run to the starter also?

Click to expand...

From the alternator it should run directly to the underhood fuse block, where it runs into a 100A fuse. Then it should go from there straight to the battery. On my truck the alternator positive wire is black, i'm guessing a poor repair attempt by a previous owner, but its a sample size of one.

As for the starter, as long as its starting fine from a charged battery I wouldn't pay it any mind. The problem with the new PCM controlled alternators is you cant test them easily. It used to be you stuck a paperclip into the field winding port and checked for voltage then, but we cant do that here.

As for the isolator, its a basic device, they usually dont go bad, and i've never known the forest service near me to use junk equipment. The isolator is probably good, its really just a watertight solenoid switch, or a bunch of 40A relays, or even a ton of solid state devices. If the alternator is putting out 14+ volts while idling with everything turned off but dives way below once you turn everything on, I would replace the alternator, or see if someone with a known good alternator is willing to swap for testing.

Sure Power 120 Amp Multi-Battery Isolator - (Part#: 12023A)

This is the isolator I have.
I figure it's just better to eliminate as many possiblities as possible. And it won't really need to be used until I need a new battery and will just buy two. I imagine it's constantly trying to charge the dead battery and straining the alternator like crazy. lol

I need to just get heavier gauge cables and all new ends. I'm kinda planning that anyway.

pwaite92 said:

Sure Power 120 Amp Multi-Battery Isolator - (Part#: 12023A)

This is the isolator I have.
I figure it's just better to eliminate as many possiblities as possible. And it won't really need to be used until I need a new battery and will just buy two. I imagine it's constantly trying to charge the dead battery and straining the alternator like crazy. lol

I need to just get heavier gauge cables and all new ends. I'm kinda planning that anyway.

Click to expand...

Thats fine, it wont hurt anything. The battery shouldn't draw that much current, but it wont hurt anything to remove it.

pwaite92 said:

Sure Power 120 Amp Multi-Battery Isolator - (Part#: 12023A)

This is the isolator I have.
I figure it's just better to eliminate as many possiblities as possible. And it won't really need to be used until I need a new battery and will just buy two. I imagine it's constantly trying to charge the dead battery and straining the alternator like crazy. lol

I need to just get heavier gauge cables and all new ends. I'm kinda planning that anyway.

Click to expand...

I replaced all my cables with 1/0 wire and have a true 1200 watt amp pushing a fifteen. And have fog lights. My lights barely dim. But Mechman Alternators have beefy alts that are like 280 compared to stock 136 and their like $400