Bad atlernator or something else?

[DadOSix]

Thanks. Can you be a bit more specific for me? I'll be back at the car tomorrow morning.

This tests the actual alternator, right? I put one lead of my meter on the alternator terminal with the bolt/nut (e.g. the "top" connection to the alternator), and the other lead to the engine block (or even the negative terminal of the battery?), and I should be able to get a reading 13+V read from the alternator, right? If I don't, is that certainly a bad alternator, or could it still be a ECM/computer issue?
-- correct! If the pcm is happy, you should show a charge condition here.

Here's what I have tested:

1. With the car off, battery measured 11.5V (it was drained). With the car started, the voltage did not change, and continually dropped until the battery died. This tells me the alternator is not charging the battery.

2. I disconnected the battery. I touched meter leads to the top bolt/cable of the alternator, and the other end of my lead to the positive terminal of the battery. I'm not sure what what I was measuring, but I was able to get a resistance reading. It was kind of all over the place, but touching them did change my meter reading - but sometimes the resistence reading read 0. If there's a specific way to test, please let me know. I can do it tomorrow.
-- doing this - you are measuring voltage drop between the battery and the alternator. Should be a steady reading - not jumping around. If zero, the fusible linkis shot, as there is no way for the alternator to get charge to the battery. Visualize if you will, a long garden hose with a splice in the middle. If the splice is open, no water for you!

I glanced at the fuse box, and all the fuses "visually" looked okay.
-- no worries! You are willing to listen and learn!

Looked does not equal ok. Must measure electrically.

Apologies for not knowing the right terms/methods here. I really appreciate all of your help.

See the link below for ScannerDanner's methodology. He walks thru much more clearly that i have a hope of.

The 'old school' method, was to ground or power the field / exciter wire and see if you get a charge.

Nowadays, they pop the alternator off and get it bench tested at the local auto parts store. Beware - all store staff are NOT ADEPT at checking the alternator's performance.

Again, if anyone has a shop recommendation near Montclair, NJ, please let me know.

Let's fix this thing!

 

[eldredg]

Don't want to be discouraging, but I seemed to recall seeing voltage regulation being controlled by ecm (engine control module) in other posts. According to a google search, this is true for 2010 KJ?

 

[nobeconobe]

I believe it is. I already ordered a new ecm. I'll know if that fixes early next week.

 

[eldredg]

Hope that fixes it. Best wishes for success.

 

[exacerbated]

Noise and burning smell could be belt tensioner. 65 dollar part and easy to repair. Needs 15mm socket. As for charging 2 bad alternators in a row not impossible but unlikely. When its running can u see if any cables or wires are hot to the touch? Anything look melted? Could be hidden corrosion somewhere.

^^^ This. For sure. Maybe? Could be.

I know it's barbaric, but I would remove the belt and spin both pulleys on the tensioner. Listen and feel for the free-wheeling grumble where there should be medium drag and smoothness. Check the belt for glazing and cracks. Watch the alternator pulley while someone else starts 'er up and jabs the throttle. Is the alternator pulley keeping up with the belt?

And before you do any of that, just push on the (non-running!) belt and see if it feels tight. I suspect the belt is doing most of its job if you're not experiencing steering or cooling issues. But what the heck? It's free to poke around.

The belt tensioner failed on our 3.7 just 4 or 5 houses down the street! So lucky! Stopped the engine, unwrapped the belt, drove it 200 feet (?) into the driveway, and performed the $80 repair (tensioner & belt) in ten minutes after getting some parts from the neighborhood auto parts store. Lucky duck, I waz.

Remember when O'Reiily was CSK (Checker Schucks Kragen)? I grew up in SoCal buying parts at Kragen, myself.

 

[nobeconobe]

^^^ This. For sure. Maybe? Could be.

I know it's barbaric, but I would remove the belt and spin both pulleys on the tensioner. Listen and feel for the free-wheeling grumble where there should be medium drag and smoothness. Check the belt for glazing and cracks. Watch the alternator pulley while someone else starts 'er up and jabs the throttle. Is the alternator pulley keeping up with the belt?

And before you do any of that, just push on the (non-running!) belt and see if it feels tight. I suspect the belt is doing most of its job if you're not experiencing steering or cooling issues. But what the heck? It's free to poke around.

The belt tensioner failed on our 3.7 just 4 or 5 houses down the street! So lucky! Stopped the engine, unwrapped the belt, drove it 200 feet (?) into the driveway, and performed the $80 repair (tensioner & belt) in ten minutes after getting some parts from the neighborhood auto parts store. Lucky duck, I waz.

Remember when O'Reiily was CSK (Checker Schucks Kragen)? I grew up in SoCal buying parts at Kragen, myself.

Thanks, I'll check these. But given that the car runs fine on a fresh battery, including the AC, and no noises/smell anymore, what are the chances it's the belt tensioner?

I drove 30 miles in battery power without issues or weird noises. It seems like the only thing wrong is the alternator isn't outputting power.

 

[nobeconobe]

Update: It was the ECM. Bought one programmed from Flagship One, Inc. Immediately fixed the issue.

 

[dhakdhak96]

Does anyone have a good shop recommendation 20 miles from Montclair, NJ (free towing only until 20miles... maybe be able to charge the battery and drive a bit more)?

 

[nobeconobe]

Allen from Montclair Motors. Honest guy. Charges $120/hr, so can get pricey if it's not clear what's going on. Extremely busy, though. Give him a call first.