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Alternator light on intermittenly

The alternator light on my 2001 Ford Escape 3.0L comes on intermittently. I’ve replace the alternator, belt, tensioner, and battery. I’ve check the wiring and the ground and there are no noticeable issues. When I first start up it never comes on. After about 30-40 minutes of driving it will start to come on intermittently. I’ve noticed that it always shuts off when taking off from a stop. I have the most trouble with it coming on while driving around the city and little trouble while cruising on the highway. I’m completely stumped. Is it possible for one of the other pulleys to be causing this if for instance some bearings were going bad and it was binding up or problems with the crankshaft slowing down the belt? At this point I’m just spitting out ideas because I’m at a loss. Any ideas would be greatly appreciated.

You have factory battery cables and no corrosion? The alternator is probably bad.

I agree with kfenimore. Unless it’s been changed in the past that alternator is 15ish years old and brushes don’t last forever.

The alternater and battery are new.

Does the car have a volt meter? If so is there a great deal of variation in the voltage and what is the voltage when the warning light comes on?

"I’ve check the wiring and the ground and there are no noticeable issues"
Did you disconnect, clean, and reconnect them, or just look at them visually?

Did you use an OEM alternator or a high quality rebuilt unit? Those auto store alternators are not that great. I would have an auto store bench test the new alternator to confirm that it is putting out the correct voltage and amperage.

I’ve even run into some factory remanned alternators that were no good

But for the most part, I’ve had pretty good luck

I've noticed that it always shuts off when taking off from a stop. I have the most trouble with it coming on while driving around the city and little trouble while cruising on the highway.

Does the batt. Light only come on at idle in gear and go off when you give it throttle? Is the vehicle idling lower than usual?

I’ve only observed the battery light coming on in gear but not always at idle. I’ve noticed it does come on more often at idle or when I’m just coasting and it does usually go off if I hit the gas hard. I have noticed that it does occasionally idle lower than normal but not always. Thanks.

Rod Knox - no volt meter in the car but I’ve checked with my handheld volt meter and it seemed to hover at or right below 12 volts when the light was on and 14 with the light off. bloody_knuckles - it’s a new motorcraft which I believe is OEM for Ford. It could still be bad. I’m trying to avoid taking it off and having a benchtest because it’s tucked snuggly in the wheel well and I have to remove the axle to get it out. the same mountainbike - I cleaned the cables at the alternator and the battery. Thanks everyone.

You have to remove the front axle to remove the battery? WOW!

The voltage should be about 12.6 volts when the engine is off and about 14-15 volts when the engine is running, ie, the battery is being charged. If you are reading below 12 volts, I’d say the battery is bad, or almost totally discharged.

I’m sure it’s the alternater that requires removal of an axle shaft to replace @BillRussell. But I believe there is a swinger bearing in that shaft that simplifies the operation. Of course my memory, like my good looks is fading.

@Rod Knox, you’re right about the alternator being new. A lapse in the derailed train of thought on my part… :smiley:

What about the belt and tensioner? Any chance of a glazed belt or shaky tensioner?

One oddity I ran into on one of my Fords some years ago involved a reman O’Reillys alternator.
The thing was fine at first but after some use the alt. light was coming on intermittently; sometimes for a few seconds and at other times for a minute or so.

I discovered this was caused by the pulley on the alternator. Visually the pulley looked fine but it would simply not get a bite on the belt and maintain it. This was detected by rotating the alternator pulley with a socket/ratchet.
Normally the pulley should be near impossible to turn. In this case the pulley could be turned without much effort against the belt. An alt. swap at O’Reillys fixed that issue.

The OP might consider trying to rotate the alt. pulley against the belt and see what happens.

BillR is correct, if the engine is running, and the alternator spinning, even at idle, the voltage you should see at the battery should be more like 13.5 to 15 volts, w/the higher voltages when the battery is partially discharged, and the lower when it is almost fully charged, like after a freeway drive where not much electrical equipment was used. Either the alternator isn’t spinning as fast as it should, or it’s faulty, or for some reason the power isn’t being delivered to the battery from the alternator. The latter could be caused by a bad wire splice in the harness between the alternator and the battery, bad connector, etc. There’s several smaller wires that go between the battery and the alternator too. Not just the big one that delivers power to the battery. Some directly, some via the ignition switch. These are for the voltage regulator operation, and those have to be making a good connection too.

I think if I had this problem and it appeared to be spinning as fast as it should, and a visual inspection of the wiring and connectors between the alternator and the battery didn’t show up anything, and the battery and battery connections tested good, I’d remove the alternator and take it back to where I bought it and ask them to place it on their test fixture. Most auto parts stores have an alternator test fixture. Tell them to knock the housing with the plastic end of a screwdriver while testing it, checking for an intermittent connection problem. Best of luck.