Battery not charging - new alternator and battery

[luigi38]

Hi all,

I got a 1999 Dodge Ram 1500 5.9 Magnum.
Well the car didn't have a battery when I bought it, so got a new battery. After a week of driving the battery died, so I took it to Advanced auto parts for an electrical test and they said the alternator was not responding under load.
So I bought and installed a new Denso alternator, got a new battery and still the car is not charging.
Went again to Advanced auto parts for an electical check and they told me the new alternator that is installed in the car is not responding under load...Since I was there I got the old alternator tested directly and that sob works great in their tester.

So, my questions, has anyone had this issue before? the accessory belt is rather tight, so that only leaves ground connectors and the battery-alternator cables (freaking expensive at the dealer pos and neg cable harnesses come about to $300).

Any feedback is welcome.

 

[JohnD72]

You might try posting this in the 3rd gen section. They will know more about your '99 and the 5.9.

 

[BossHogg]

If you have a voltage meter, measure the voltage across the battery with the engine running, should be greater than 13.2 depending on the battery's charge state. This indicates the charging system is working.

Watch the meter for a while looking for voltage drops, sometimes a single cell will fail in a battery (new ones too) off and on, they actually change polarity.

Look up your charging system wiring here;
https://techauthorityonlinedemo.extra.chrysler.com/service/repair/wiring/view/classic.htm

 

[ramenthusiast]

You might try posting this in the 3rd gen section. They will know more about your '99 and the 5.9.

Actually, a 1999 would be a 2nd gen truck.

 

[luigi38]

This is the 2nd battery I got from Autozone, and same results.
So when the car is running, I can see the needle go to 14v, when I turn on the lights, heater, heating mirrors it drops to about 10-11v and it seems the alternator cannot keep up during loads in my truck....If I take the alternator off and get it tested it passes the test from Advanced Auto, works fine under normal conditions and under load...

 

[luigi38]

This URL only goes back to 2010, I need another 11 years of info, mine is a 1999.

If you have a voltage meter, measure the voltage across the battery with the engine running, should be greater than 13.2 depending on the battery's charge state. This indicates the charging system is working.

Watch the meter for a while looking for voltage drops, sometimes a single cell will fail in a battery (new ones too) off and on, they actually change polarity.

Look up your charging system wiring here;
https://techauthorityonlinedemo.extra.chrysler.com/service/repair/wiring/view/classic.htm

 

[dodge dude94]

Only thing I can think of would be the PCM at this point.

Download this:
http://www.ramforum.com/f77/2nd_gen_service_manual-986/

 

[luigi38]

Only thing I can think of would be the PCM at this point.

Download this:
http://www.ramforum.com/f77/2nd_gen_service_manual-986/

Replacing the PCM is an expensive proposal.

Someone recommended me to clean all grounds from the battery to the chassis, and possibly add an extra ground from the battery to the chassis and from the chassis to the block.
Anyone think this can help?

Anyone think it can be the tensioned pulley? the belt looks a tiny bit lose, it maybe gives out about and inch if pressed on.

 

[dodge dude94]

Replacing the PCM is an expensive proposal.

Someone recommended me to clean all grounds from the battery to the chassis, and possibly add an extra ground from the battery to the chassis and from the chassis to the block.
Anyone think this can help?

Anyone think it can be the tensioned pulley? the belt looks a tiny bit lose, it maybe gives out about and inch if pressed on.

Indeed it is, however the PCM IS the voltage regulator, and if it's not letting the alternator respond, that's an issue.

Adding chassis ground and cleaning them can help, definitely cheaper too.

 

[luigi38]

ok it seems Ima be trying the ground cleaning this weekend.
If that does not work, I was thinking of replacing the belt and pulley tensioner.
and if that doesn't work, then I may have to go to the Dealer and see what they say....
thanks for the help.

 

[dodge dude94]

Your tensioner might be stuck. I know mine was. Took a ratchet with a 5/8th socket and pulled it slack, then let it pop back out and my belt was better.
It's worth a shot.

 

[jbmobbs]

Dodge had 3 or 4 different alternators through the years. They may have sold u one that doesn't create enough voltage while under load

Sent from my DROID RAZR using Tapatalk

 

[Merc225hp]

Clean your grounds like you said and then test, but see this post below this is where you are heading to.

Only thing I can think of would be the PCM at this point.

As the shop checked your org alt and it was fine with a bench test but not working in the truck then this points straight to the pcm.

 

[LaurenMagnum360]

worse case scenario is return the new alternator and get a chevy 1 wire alternator, and play around with some flat stock steel to mount it to your engine. no more ecu controlled Voltage Regulator, or you can get a ford external voltage regulator used on 70-80's trucks and if you know some basic electronics, you can open your alternator and convert it.

 

[luigi38]

Well I found the problem and it was the obvious.
I cleaned the grounds and same problem persisted.
Then noticed some slack on the belt and the tensioner was shot....my crappy mechanic told me it was fine.
Needless to say, I changed the tensioner and belt which was a piece of cake on this car, this solved my problem.

Now the beast charges no problem.

thanks to all for the help.

 

[APBTMAXX]

Hi guy, i was reading this post because something weird happening to me with my 2008 dodge ram 2500 cummins 5.9, last days i have been instaled a kenwood double din unit in it, and last night i was watching with hight volume a video with engine off and switch key in accesories for about an hour, and when i start the engine this start to spin kinda low but finally started, the very rare thing here is if the engine running, why the alternat doesn't charge!!!!!!!, any idea guys???
This is that i thing to happen: if the chrysler charging system is designed to supply power to all devices of the truck and charge the batteries just in a surface level, could be 95% of his capacity, and when, for a several reason or batteries are too old, you is taking power from batteries with engine off, and the % level down below the 95%, the pcm directly don't exite the alternator, or change batteries, or charge them til they reach at least 95% of his charge, maybe i'm wrong, what you say about this??? Thanx in advance.-

 

[APBTMAXX]

FIXED!!!! was both batteries!!! and was as i wrote above, the pcm exite the alternator only if both batteries are at 95% of his charge or more, below that, the pcm let the alternator anactive until recharge the batteries individually or directly change the batteries, this cause that the check gages first and then check engines lights on too.-

 

[ramtough1963]

What was the final outcome?