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Michael Butts

Not Charging Issue

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Hi,

I purchased a 2001 Mercury Sable with the 3.0 about eight years ago with just 11,000 miles on it.  It now has 87,000 and I have an electrical issue.  I first discovered it during the pandemic lockdown when the car had been not driven for two weeks.  Battery was completely flat.  Fully charging it with an intelligent battery charger seemed to fix the issue.  I left it on a battery tender while I wasn't driving it.

When I had another incident with charge too low to start the car, I tested for parasitic draws and the alternator's output.  Since the draw is just 0.50A with key off and the alternator output at the battery's terminals is 14.5V, I figured it must be the battery.  It's a Motorcraft purchased from the Ford dealer and they tested it as good.  I also took it to a Batteries Plus store and they said the same thing.

I fully charged it out of the car and reinstalled it.  It worked for a couple of days, but I could tell from the starter speed that the battery was losing charge.  On its last trip out, it started, but left me stranded 5 miles away when I attempted to restart it after going into a store for less than 5 minutes.

I don't get a warning light on the cluster, the serpentine belt is a few years old (it's in good condition and has good tension), I don't hear any sound from the alternator (like bad bearings).  With engine running at 2,000 RPM, the alternator puts out 14.3 to 14.5V even with headlights, fog lights, blower, map lights, & radio on.

The numbers:

Battery after 12 hours at rest: 12.42V
Alternator output at idle or 2,000 RPM measured at battery posts: 14.5V
Current with key off: 0.50A
AC voltage at 2,000 RPM measured at battery posts: 0 (this was something I read that would show possible rectifier problems)
Battery: Motorcraft 100 month battery, 42 months old
Alternator: it looks original

Since the alternator isn't super convenient to swap out, I'm looking for alternatives to throwing parts at it.  Does anyone have any ideas on this?

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Old school test for charging system.

 

Disconnect battery when car is running.

Does it die? Alternator related

Stays running? Battery related

 

Have you done a thorough cleaning of the battery cables and terminals? You may just have oxidized connections preventing proper chargeback.

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6 hours ago, Michael Butts said:

Hi,

I purchased a 2001 Mercury Sable with the 3.0 about eight years ago with just 11,000 miles on it.  It now has 87,000 and I have an electrical issue.  I first discovered it during the pandemic lockdown when the car had been not driven for two weeks.  Battery was completely flat.  Fully charging it with an intelligent battery charger seemed to fix the issue.  I left it on a battery tender while I wasn't driving it.

When I had another incident with charge too low to start the car, I tested for parasitic draws and the alternator's output.  Since the draw is just 0.50A with key off and the alternator output at the battery's terminals is 14.5V, I figured it must be the battery.  It's a Motorcraft purchased from the Ford dealer and they tested it as good.  I also took it to a Batteries Plus store and they said the same thing.

I fully charged it out of the car and reinstalled it.  It worked for a couple of days, but I could tell from the starter speed that the battery was losing charge.  On its last trip out, it started, but left me stranded 5 miles away when I attempted to restart it after going into a store for less than 5 minutes.

I don't get a warning light on the cluster, the serpentine belt is a few years old (it's in good condition and has good tension), I don't hear any sound from the alternator (like bad bearings).  With engine running at 2,000 RPM, the alternator puts out 14.3 to 14.5V even with headlights, fog lights, blower, map lights, & radio on.

The numbers:

Battery after 12 hours at rest: 12.42V
Alternator output at idle or 2,000 RPM measured at battery posts: 14.5V
Current with key off: 0.50A
AC voltage at 2,000 RPM measured at battery posts: 0 (this was something I read that would show possible rectifier problems)
Battery: Motorcraft 100 month battery, 42 months old
Alternator: it looks original

Since the alternator isn't super convenient to swap out, I'm looking for alternatives to throwing parts at it.  Does anyone have any ideas on this?

Since the volts are fine when running, highly likely not the charging system. That leaves grounds, and current draw when not running. 0.5A way too much. 

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Hi,

Sorry about the delay in answering.  Thanks for the suggestions!

@zenriddles I am leery of yanking a cable while the engine's running for fear of frying electronics.  The battery terminals are clean (when checking the water levels 1-2 times a year, I clean it thoroughly and coat the terminals with CRC battery terminal protectant).

@-chart- I checked for a bad ground by connecting a volt meter from the disconnect negative cable and the negative battery post.  It was within 0.1 V of the reading from the + & - battery posts.

I think I'm going to pull the wheel and splash guards under the RF fender to see if I can get a better look at the alternator and check for voltage drops.

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I took at look at a few Youtube videos on removal of the alternator and decided it's not worth an all day effort just to take a look at the alternator. 

I'll put the car on a Battery Tender when it's going to be parked for more than 2-3 days and I'll put "fold self into thirds, cram under dash, pull fuses until draw is found" on my to do list.

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