Alternator mystery

twotrack

twotrack

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Oct 17, 2020
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Location
SE Wisconsin
Check gauges light was on. Looked like battery charge level was about 10 V on the gauge. Like this for weeks. First noticed after a carwash.
Took to Advanced Auto to check the alternator. They have me rev the engine to 3000 rpm. They say the alternator is producing zero charge. They don't have it in stock so I decide to drive to the nearest town over.
When I start up the car, the charge level reads 14 V. Check gauges light is off. I drive to the next town anyway (about 15 minutes) to see if it goes back down to 10 V. It does not.
I have the Advanced Auto in the next town check it. They say the alternator is producing zero charge. They say that they have never seen an alternator produce zero charge and that it might be a sensor or a connection.
I drive home (about 20 minutes). No check gauges light and constant 14 V. 12 V when just on. Code returns P 1682.
So it seems "fixed", but I have zero confidence in it. Any explanations for this weird behavior? How much should I worry? (I want to drive it 250 miles up north to a cabin next weekend.) What else should I do or check? I don't want to replace the alternator if not necessary or if it is a sensor or connection instead.
Thanks for any assistance.
It is a 2003 TJ Sport (inline 6, 4.0L)
 
A loose, dirty, or corroded battery connector can cause several problems for the alternator. I'd physically remove both and wire brush both battery posts and the insides of both connectors. Then reinstall both and insure both are tight enough that they can't be moved with even considerable hand pressure.

A battery brush has both male and female wire brushes to make the job easier.

In other words check the easy things first like the connections since they can and do cause alternator problems. Only after doing them, and don't just look at them since bad connections can look fine, then you can start looking at the other possibilities.
 
Remember charging is controlled by the ECM so I would check the (3) 32 pin ECM harness connectors for oxidation and ensure the connectors are firmly snapped into the ECM receptacles. Also check the field charge wires on the alternator for cleanliness.
As Jerry stated above; battery cable clamps, terminals, along with the block ground wires to the left of the oil filter and the ground cable to the firewall stud.
 
Do you have any noise whatsoever? Even in the slightest, smallest bit...???

Corrosion on battery terminals?

Some food for thought. We get a lot of electrical charging issues into the shop. When testing the alternator we put the tester on and let it run with all accessories on. High beams, heated seats, defrost front and rear, radio. In other words load the system with the most accessories the driver may be using at one time.

Often times we find a satisfactory charge in the first couple minutes. 15 minutes later we see the charging has now dropped from low 14's to low 12's or even further.

Had someone just check it for a minute or two they'd say the alternator is good. Once the alternator internals get really warm after 10-15 mins the windings charge output starts breaking down significantly.

If you're able to do your own test of it watch it under duress with a partner adding accessories gradually and watch the readings.

A good alternator will take a
quick drop when an accessory is turned on but will recover within about a second. Udually less than a second. You'll see a 1-1.5 voltage drop real quick but recover back to 14.18 or there of.

So watch your charging and have your helper turn on head lights, then add high beam, then add heat/def combo, then radio, dome light, and so on taking note of the behavior after each accessory is turned on.

You will know a whole lot more about WTF is going on with your charging system just by the above extended alternator test.

Good luck

P.s.

We also get a lot of issues come in with this and youd6be surprised at how many actually have loose connections. Literally grabbing and twisting the terminal and it just turns with moderate hand force. You can work it back forth abd the terminal just come off.

I'm not suggesting you don't know how to tighten a battery terminal but it does happen and those people swear its anything abd everything but their connections.

Again, good luck
 
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Thank you all for the suggestions.

In the name of starting with the easy things first, I took off the battery clamps and cleaned them and the terminals until shiny. I tightened them back on very tight. I also lightly wire brushed the 2 pin connector and heavily brushed the battery wire connection at the alternator. I checked the ECM connectors and they looked fine, I plugged them back in until clicked.Code was cleared. I took it for a short drive and turned on all electrical things I could think of. Ran at 14V. Checked when I got home and still no code.

If I run in to problems, my next steps would be to do what I didn't do. I did not check the block ground wires to the left of the oil filter (because the whole bolt was coming out so I think you have to hold it so I'm lazy and gave up) and the ground cable to the firewall stud (which I didn't find).

I don't have a tester to do the test Rubicon88 suggested.

My best guess is that there was a film at the battery terminal, and when the first guy connected the tester he bumped it enough it make the connection again.

Marking tentatively solved for now. If the problem comes back I will post back to this thread.
 
OK. Not solved.

Take it for a drive and it runs really rough, gives code 1391 camshaft or crankshaft sensor. I take off the old camshaft sensor (because that is easy and which, btw, is exactly my level of mechanical ability) and there is black metal filings magnetized to the metal part of the sensor. I'm pretty sure I could have just cleaned them off and put it back in but I put the new piece in anyways. I clear the code. I drive it is somewhat rough at first, especially around 50mph but the more I drive the more it seems to smooth out.

In the meantime, my voltage is back down to 10V. Headlights are dim. Every once in a while it will jump back up to 14V and the lights will brighten. Then back down. I thought maybe it was related to high RPM and 14V but when I tried to rev it up, no. Anyways, back to 10V and code 1682. I suppose it could be the two ground wires I haven't checked yet. But honestly I'm just wanting to put in a new alternator. Would that be a waste without knowing for sure that is what it is?
 
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twotrack said:
OK. Not solved.

Take it for a drive and it runs really rough, gives code 1391 camshaft or crankshaft sensor. I take off the old camshaft sensor (because that is easy and which, btw, is exactly my level of mechanical ability) and there is black metal filings magnetized to the metal part of the sensor. I'm pretty sure I could have just cleaned them off and put it back in but I put the new piece in anyways. I clear the code. I drive it is somewhat rough at first, especially around 50mph but the more I drive the more it seems to smooth out.

In the meantime, my voltage is back down to 10V. Headlights are dim. Every once in a while it will jump back up to 14V and the lights will brighten. Then back down. I thought maybe it was related to high RPM and 14V but when I tried to rev it up, no. Anyways, back to 10V and code 1682. I suppose it could be the two ground wires I haven't checked yet. But honestly I'm just wanting to put in a new alternator. Would that be a waste without knowing for sure that is what it is?
Click to expand...
I'm surprised at this point you haven't tried a different alternator.

What is your location in Wisconsin. A nearby town?
 
I suspect one of two things:

1st, the alternator could be bad. If the alternator is bad, generally it still produces some current, but it’s possible there is a short in the field circuitry somewhere preventing it from charging. Alternator replacement will correct this issue.

2nd, the PCM charge controller circuit is bad. Most likely it is a wiring fault somewhere between the PCM and the alternator, but it’s not uncommon for it it be a fault with the PCM itself. PCM replacement is the correct way to correct this issue; however, an external charge controller like linked below will solve the issue for a tenth of the cost, but will take a bit of wiring ingenuity.

https://alternatorparts.com/external-voltage-regulator-high-output-alternator-kit.html
I believe there is a way to short some pins to bypass the charge controller on the TJ alternator to test it
 
Replaced the alternator. No codes. No check gauges. Running 14V.
I believe it is solved and it was the alternator all along. Will post back if not solved.
Thanks to all for trouble shooting suggestions.
 
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