Electrical problems

[Jonathon Eck]

My 2000 diesel Ram 2500 isn't charging.

I've been googling it and I've yet to see any mention of the defective alternator output voltage range.
I measure 33 VDC at the alternator output wire.

At the batteries (1 year-old Optima red-tops) I only get the resting battery voltage, engine running. That's what shows on the dash meter too. About 12.5.

I recharged the batts seperately, and connected only to the charger on slow 2A setting.
They don't seem to have been damaged yet, the charger is newer and it said they were good.

That's the problem I started with, and it's the same problem I have now. Here's what I've done to try and fix it:

1. Replaced the alternator. Took the old one to autozone afterwards and had them test it. Came back bad everytime on their machine.

The replacement
Amazon product ASIN B00S9JDLQO
I got a cheap one thinking that it would be less of a loss if I somehow fried it troubleshooting the issue. That, and I wasn't 100% sure the old one was bad or just mis-regulated.

2. Replaced the battery cables and engine ground cable ends.
I had the TC lock-up issue a few years back. I re-routed the ground behind the alt and that fixed it. So I know my truck is mid-west rusty and all the connections are suspect.

Ordered 1/0 bulk cable and lugs/crimper, etc. off Amazon.
wire-wheeled the corrosion on the bolts/block, then slathered DC-4 (Di-electric grease) on everything and in between connections. Heat-shrinked generously.
Installed new military style battery terminals on brushed and greased posts.

3. Replaced CKP (crankshaft position sensor).
My truck was occasionally throwing codes for ckp in the past. I cleared it a couple times last year and then it just went away.
I bought a new sensor and put it in the glove box, and there it stayed.

When I started with this issue, I read from Mopar Man that the ckp can affect charging. So I pulled the starter, fought like holy hell to get the old ckp out, and replaced the ECM ground lug while I was in there.

+Hoping that the above worked, I started the truck for the first time since changes.
Unusually long "Wait to start" light, for summer.

No fix.
Alt output wire shows 34 vdc, dash shows 12ish.

**** **** ****.

4. Bought an external voltage regulator (VR) and pig tail to follow internet recipe for external VR fix.
I have two trucks so I can afford the downtime later to send in the PCM for repair.

Hooked the blue (top of the pyramid connector) wire into the stock alt blue wire, which I verified was switched to 12 vdc. So the blue wire goes to switched 12v, the alt control connection, and the VR. 3-way connection.

Capped the green wire coming from the PCM to the alt. Connected the green from the VR to the green alt connection.

Ground off the paint and DC-4'd around the stock air cleaner studs (pax fender-well) to mount the external regulator. Ran a nice fat ground lug wire from the regulator mount to nearest alternator housing bolt.

5. Started truck. Same problem.

Any ideas?

 

[petersonj]

Are you saying that you are seeing 34 volts at the output terminal? If that is so, there is an open circuit from that terminal to the driver side battery. Have you checked the 140 amp fuse in the PDC where the alternator wire enters the PDC?

If this fuse is blown, the alternator cannot charge the batteries.

Have you put a multimeter on each battery while the truck is running to check for voltage?

- John

 

[Topzide]

With alternator issues, I wouldn't trust Auto Zone to test it! These are counter people and not repair people! Should've taken to a shop that does starters and alternator rebuilds. The rebuilt units being sold the national chains are a quarter flip on quality! I'll agree with @petersonj about open circuit. Alternator was putting out a voltage that it thought was needed. Could've been internal VR starting to go out. 1 diode failure in VR can cause havoc. Alternators produce A/C voltage that's changed to D/C through a rectifier. I know that you may already know that but worth repeating for others that may search this thread and provide them the help they need. YES, grounds are a huge problem in the rust belt. Extra or larger grounds help with the current flow, charging and performance issues. Look for tracking in fuse box and corrosion on connectors also. Good luck!

 

[Jonathon Eck]

My 2000 diesel Ram 2500 isn't charging.

I've been googling it and I've yet to see any mention of the defective alternator output voltage.
I measure 33 VDC at the alternator output wire.

At the batteries (1 year-old Optima red-tops) I only get the resting battery voltage, engine running. That's what shows on the dash meter too. About 12.5.

I recharged the batts seperately, and connected only to the charger on slow 2A. They don't seem to have been damaged yet, the charger is newer and it said they were good.

That's the problem I started with, and it's the same problem I have now. Here's what I've done to try and fix it:

1. Replaced the alternator. Took the old one to autozone and had them test it. Came back bad everytime on their machine.
The replacement
Amazon product ASIN B00S9JDLQO
I got a cheap one thinking that it would be less of a loss if I somehow fried it troubleshooting the issue. That, and I wasn't 100% sure the old one was bad or just mis-regulated.
I know better than to buy cheap parts but money doesn't grow on trees around here!

2. Replaced the battery cables and engine ground cable ends.
I had the TC lock-up issue a few years back. I re-routed the ground behind the alt and that fixed it. So I know my truck is mid-west rusty and all the connections are suspect.

Ordered 1/0 bulk cable and lugs/crimper, etc. off Amazon.
wire-wheeled the corrosion on the bolts/block, then slathered DC-4 (Di-electric grease) on everything and in between connections. Heat-shrinked generously.
Installed new military style battery terminals on brushed and greased posts.

3. Replaced CKP (crankshaft position sensor).
My truck was occasionally throwing codes for ckp in the past. I cleared it a couple times last year and then it just went away.
I bought a new sensor and put it in the glove box, and there it stayed.

When I started with this issue, I read from Mopar Man that the ckp can affect charging. So I pulled the starter, fought like holy hell to get the old ckp out, and replaced the ECM ground lug while I was in there.

+Hoping that the above worked, I started the truck for the first time since changes.
Unusually long "Wait to start" light, for summer.

No fix.
Alt output wire shows 34 vdc, dash shows 12ish.

**** **** ****.

4. Bought an external voltage regulator (VR) and pig tail to follow internet recipe for external VR.

Butt-connected the blue wire (top of the pyramid connector) from the VR into stock alt blue wire, which I verified was switched to 12 vdc. So the blue wire goes to switched 12v, the alt control connection, and the VR. 3-way connection.

Capped the green wire coming from the PCM to the alt. Connected the green from the VR to the green alt connection.

Ground off the paint and DC-4'd around the stock air cleaner studs (pax fender-well) to mount the external regulator. Ran a nice fat ground lug wire from the regulator mount to nearest alternator housing bolt.

5. Started truck. Same problem.

Any ideas?

Are you saying that you are seeing 34 volts at the output terminal? If that is so, there is an open circuit from that terminal to the driver side battery. Have you checked the 140 amp fuse in the PDC where the alternator wire enters the PDC?

If this fuse is blown, the alternator cannot charge the batteries.

Have you put a multimeter on each battery while the truck is running to check for voltage?

- John

 

[Jonathon Eck]

Yes, 34 vdc at the output.
I’ve checked the batts running and it’s just the resting batt voltage.
I’ll check that fuse, thanks.

 

[Ozymandias]

How is the continuity of the wire from the alternator to the battery?
It is impossible to read 33V at the alternator and 12.5V at the battery at the same time as it is one circuit.
Maybe the fusible link in the wire burnt up.

 

[petersonj]

Yes, 34 vdc at the output.
I’ve checked the batts running and it’s just the resting batt voltage.

That says the connection has been lost between the alternator output and the PDC or lost between the PDC and the driver side battery. The PCM regulates battery voltage to around 14 volts (dependent on ambient temperature). The PCM senses voltage from the passenger side battery.

Since your battery voltage on both batteries is well below the 14 volt regulated voltage with the engine running, the PCM is telling the alternator to increase output. The alternator does, but the current has nowhere to go - hence the excessively high 34 volts dc.

If the 140 amp fuse is blown, then either the original alternator had a direct short circuit to ground, or someone unintentionally shorted the alternator output terminal to ground while doing some work in the proximity of the alternator.

Either way, find and fix the open circuit and then start over with diagnosing. Don't change anymore parts.

- John

 

[Jonathon Eck]

Yep, the 140A fusible link is open. Humble pie for me tonight.

This problem started when I was driving the truck home from having the oil changed at a shop. The dash voltmeter would fluctuate between 12ish then 0, then it just stayed at 0.

But, it was also in the shop to have the ABS looked at and an AC leak chased.

Backstory:
I had loaded up an old workbench to give to a friend.
I was getting rid of things in a hurry to prepare for old-barn demolition and house addition excavation/construction.

As soon as I left to drive it over, I was getting the ABS and Brake lights. I stopped at the top of my street to take a look. When I shut off the truck, the ABS pump stayed on. WTF? Never seen that before.
Plenty of brake fluid. The pump would only go off by disconnecting power from it. It turned right back on when re-connected.

I couldn't figure it out so I returned to base and the bench stayed in the bed.

I was also planning to use the truck to pick up specialized materials later that week from out of town. Very bad timing so I decided to punt the truck to a very reputable shop and rent what I needed to haul the supplies.

The shop came back telling me I needed brake pads, the ABS controller was fricked (it is, sending it out for repair this week) they couldn't find the AC leak but had charged the system, and done the oil change. I told them don't worry about the pads, I'll come get it.


I ordered a new fuse yesterday and will see what I get with that. Then I will disconnect the external voltage regulator and reconnect to the PCM to see if that works.
I might even put the old alt back in to test it too.

I didn't find evidence of shorts in any red wires when I replaced the cables. I'm going to look for a boot to put on the alt output terminal.

Thanks for the advice gents!

 

[petersonj]

It is possible to have shorted the alternator output terminal to ground with a tool when the oil filter was replaced. That would have blown the fuse instantly. It is also possible that it could have failed with age.

If so, my guess is that your PCM and original alternator will work just fine. Be sure to let us know.

- John

 

[KeggerTx]

Good thread Jonathon Eck. Please let us know the outcome after replacing the fuse! Enquiring minds want to know!

 

[Topzide]

People have asked me why I don't wear my wedding ring when working on anything. I don't want to get caught on something were you can't pull your hand out or short something out! Back in the day, never wore any jewelry when being in a energized panel box! Just to many what ifs! Hope the fuse solves the mystery! Good learning thread on not to throw parts but chase down the cause! TDR to the rescue again with all the experience out there!

 

[Jonathon Eck]

Finally got the fuse put in tonight.
It's charging but hopping around between 14.75-15.25.

Hopefully I can put it back to stock tomorrow and re-test.

I'm adding on to my house right now so I'm slammed. Plus full-time job, domestic commitments, etc.

I appreciate all the advice here. I'm guilty of shot-gunning, agreed.

Replacing the alternator without proving it bad was a mistake. I went down the google rabbit-hole when I couldn't be near the truck to check things.

The truck already needed fresh cables and terminals though, I'm glad that's done. I used the breakdown as motivation to get the grounds redone, decrease the likely-hood of gremlins.
Of course, I should have figured out exactly what's wrong before I changed anything, ideally. I know, I know.

 

[Ozymandias]

Thats okay to see that, it's temperature compensated. So alternator output is not only by battery state of charge.

 

[Jonathon Eck]

Sorry for the delay.
I finally got my Dodge fixed!
I just cut the external voltage regulator out and re-spliced the original alternator wiring and it is charging just fine.

I think my batteries might be damaged. They were at 10.3 vdc when I came out here today.
I put the charger on it at 2A and did some other stuff for a couple hours.

After I changed the wiring back, I started it and was showing 12.7 at first then climbed to 14 within about 10 minutes of idling. This was measured on the driver's side battery posts.

I left the MM hooked up to the batt after I turned the engine off. Within about 20 minutes, the vdc was down to 11.99.

I hooked up the charger again at 2A and I'm going to let it run until it says it's done.
The charger is a newer Schumaker and has settings for AGM, bad battery, etc. so we'll see what that says.

 

[Jonathon Eck]

Also, I sent the ABS controller out to Circuit Board Medics and they did a great job delivering exactly what they promised. I would definitely recommend them.