ALTERNATOR NOT CHARGING NEED HELP

[Anthony Lowry]

Sorry for the all caps in the title but I need as much help as I can get as this truck is my only way to and from work.

The truck is a 2009 ram 1500 5.7L 2wd

So basically the alternator is not charging the battery at all. Just a few minutes of driving kills my battery. I did try all the simple stuff already I’ll go ahead and type the whole timeline.

Yesterday I was out getting quotes on some work I need done. Then when I go to start my truck again it ticks quite a few times and my battery light comes on. So I headed straight over to the oriellys by my neighborhood and one by one each light started turning on on the dash trac control, ABS, airbag, etc. By the time I pulled in to a parking spot the truck was barely running. So I had the battery tested and it was completely dead. Got a new one through warranty and also noticed a little bit of black burn marks around the alternator pulley. So I drove about 5 minutes home and same thing started happening again. So today I pulled the alternator out and went and bought a new one. Hooked it up and everything seemed good. The truck idled for a long time on its own and then I went for a test drive. Not even 5 minutes in and same thing. Lights started coming on and battery was dying. So I got the truck home and turned it off. The battery was too dead to start again so I Jumped it off of another car and busted out the meter. The battery started off at about 12.2v and slowly dropped down to under 8v but wouldn’t really drop past 7.3v. I checked and made sure I hooked the alternator up correctly which it is just a plug and one wire so I’m pretty sure I couldn’t of messed that up. So I tried the old trick of popping the positive battery cable off to check the alternator and the truck shut right off (I was later told this is bad cause it can blow modules). Anyways I took the alternator back up to oriellys and they tested it a few times and it passed every time. Now I’m completely lost.

I’m pretty young and not that knowledgeable past what I have just stated. So at this point I believe it may be the pcm not telling the alternator to charge as the voltage regulator is within it. While my mechanic friend said it may be the fuse box. While another buddy said it may be the pcm and to run an external regulator.

 

[Brandon-w]

The one wire connection on the alternator. The little one not the one that goes to the battery. Test it! There should be 12v there telling the alternator to activate the field and start charging. If you don't have voltage here you can trace it back see if there are any chafged or broken spots. Once ur traced rohjt back check for voltage there. Truck running/or key on during all this testing. If you want you could use a piece of wire and go from battery pos to alternator field wire terminal. Make sure the connector is disconnected before you add power to alternator as you don't want to back feed that wire to the pcm. If you have power there and it starts charging properly you know 100% it's that wire not giving power.
Hope this makes sense.
If not I will try to simplify.
Brandon

 

[Elevated 2013]

Check all of your grounds. The battery gets return charges from them as well. The PCM isn’t an on/off switch. As much as it monitors the voltage and charge of the battery. The alternator is pretty self sufficient for the most part. Check your ground wires to the frame and engine starting with the battery cable from the battery negative to ground.

 

[Elevated 2013]

Btw, I’m not calling your buddies wrong when they talked about the PCM. It’s just fairly unlikely.

 

[Brandon-w]

Btw, I’m not calling your buddies wrong when they talked about the PCM. It’s just fairly unlikely.

The old school 90s dodges did have the regulators in the pcm but thdy don't do that anymore as far as I know. Not wrong but wrong models. Lol

 

[Cableman]

The old school 90s dodges did have the regulators in the pcm but thdy don't do that anymore as far as I know. Not wrong but wrong models. Lol

The 2nd gen had external regulators, 3rd gen they went to the PCM.
My 3rd gen had a fluctuating voltage issue i only notice when i installed a jl audio amp and it would shut off if it went over 15v. I ended up installing an external vr and just had to deal with the ck gauge light.

 

[Anthony Lowry]

The one wire connection on the alternator. The little one not the one that goes to the battery. Test it! There should be 12v there telling the alternator to activate the field and start charging. If you don't have voltage here you can trace it back see if there are any chafged or broken spots. Once ur traced rohjt back check for voltage there. Truck running/or key on during all this testing. If you want you could use a piece of wire and go from battery pos to alternator field wire terminal. Make sure the connector is disconnected before you add power to alternator as you don't want to back feed that wire to the pcm. If you have power there and it starts charging properly you know 100% it's that wire not giving power.
Hope this makes sense.
If not I will try to simplify.
Brandon

okay so what I got from this was disconnect the plug on the alternator and run a piece of wire from bat + to wire on alternator to check and make sure that wire is good.

Then for “the little wire” do you mean one of the ones on the plug?

 

[Anthony Lowry]

The old school 90s dodges did have the regulators in the pcm but thdy don't do that anymore as far as I know. Not wrong but wrong models. Lol

Yeah like I said kinda young don’t know a lot of this. Just read on one of the forums that the regulator was in the pcm.

 

[Brandon-w]

Is there a brown/grey wire off your alternator. The little plug. Not the one that charges your battery?

 

[Brandon-w]

Here is a wiring diagram.

 

[Anthony Lowry]

Check all of your grounds. The battery gets return charges from them as well. The PCM isn’t an on/off switch. As much as it monitors the voltage and charge of the battery. The alternator is pretty self sufficient for the most part. Check your ground wires to the frame and engine starting with the battery cable from the battery negative to ground.

Yeah I will go through in the morning and check all of my grounds again. There is a wiring harness behind the driver side wheel well which may have gotten wet. But with it being under the truck I don’t see this being an issue as it must have gotten wet hundreds of times before.

Is there a brown/grey wire off your alternator. The little plug. Not the one that charges your battery?

I’m not sure I’m at work rn I’ll have to check when I get home in the morning.

 

[Brandon-w]

Sounds good man. Also check fuse 31. I won't be far from my phone tomorrow so I'll reply quick. [emoji106]

 

[Anthony Lowry]

Sounds good man. Also check fuse 31. I won't be far from my phone tomorrow so I'll reply quick. [emoji106]

Very much appreciated. Hopefully I can get this figured out tomorrow.

 

[Anthony Lowry]

https://www.justanswer.com/dodge/ajwhi-2009-dodge-ram-2500-pick-5-7-hemi-alternator.html

So it’s 3am and I’m bored at work so I’ve been researching any possible reason that the truck may be doing what it is doing and I ran across this thread. It sounds good way to test the pcm and determine whether or not that is the culprit so I’ll try what he did as well tomorrow. Appreciate the help Brandon-w and Elevated 2013. Fingers crossed it’s not the pcm and just a loose wire or something.

 

[Elevated 2013]

Once you double check and verify that you have a good battery (you may want to test it and try to charge it for a bit) then that might be a good way to diagnose what’s going on with the alternator/wires/pcm. I hope it’s just a bad wire or fusible link!!

 

[Anthony Lowry]

Once you double check and verify that you have a good battery (you may want to test it and try to charge it for a bit) then that might be a good way to diagnose what’s going on with the alternator/wires/pcm. I hope it’s just a bad wire or fusible link!!

Im waiting on the next shift to get here and I’ll be going straight home to work on it. Good thing is an ECU doesn’t cost nearly as much as my old 5.7 challenger

 

[Anthony Lowry]

Okay so this is where I’m at right now. Jumped the truck off of my buddies car and took off the cables. As soon as I took off the cables the battery started dying fast. Alternator+ and battery have same voltage so the wire connecting the two is good. Unplugged the alternator plug with the two wires running to the pcm. Touched the prong for the red/grey wire (gen sense wire) on the alternator and it had voltage then touched the prong for the brown/grey wire (gen field ctrl wire) and it had no voltage which it shouldn’t because that is the wire for the alternator to tell it when to charge. Then put the plug back on and once again red/grey had voltage but the brown/grey had no voltage which it should because it should be telling the alternator to charge. I’m about to bypass the pcm and run a hot wire to the prong telling it to charge and see what happens.

 

[Brandon-w]

Yes run a wire to that prong that tells the alternator to charge. Any shop will do that to test it to make 100% sure that's what it is. I've seen guys run that wire to a key on ignition to bypass it. Just make sure if you do that it's a key on power that works with the remote start if ya have it. That way u won't remote start it and kill the battery.

 

[Anthony Lowry]

Alright I did the direct wire and as soon as I hooked it up instantly 13v. So it seems to be the pcm. Although I do have one fuse that is blown fuse J02 something for the trailer. And then I had a two prong fuse in m49 and the diagram seems that it needs a 3 prong and the socket has 3 holes. So I’m going to do those two to rule out any possible reason before finding a new pcm.

 

[Brandon-w]

Sounds good. Atleast you got it mostly figured!