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Old 03-07-2007, 11:28   #1 (permalink)
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Smoking Alternator

I have a 1998 Taurus SE with 111k miles and the common 3.0 liter V6 (not DOHC). I bought it 3 months ago. I noticed it had a brand new alternator. The seller said he just had to replace it a month ago (Nov 06). Shortly after buying the car, it sat for 3 days and the battery was dead. I bought a new battery and tested for current draw while parked. When I connected the ammeter, the car would draw about 0.4 amp for about 5-10 seconds, then drop to 0.18 amp and stay there. What could be drawing 180mA when it's just sitting there?

This morning, I smelled something burning while it was idling and I was scraping the ice off the windows. I popped the hood and found the alternator smoking and darkened from heat. I could have roasted a chicken over it. The windings were copper colored, now they're dark brown.

I priced alternators and they go for about $120 and up. Is there a common known problem that caused the new (rebuilt) alternator to fail? I don't want to buy a new alternator just to watch it burn up.

Any troubleshooting suggestions would be welcome. I have a pile of tools and test equipment.....Thanks!
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Old 03-07-2007, 23:49   #2 (permalink)
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Re: Smoking Alternator

The clock, theft system and the memory to the computer will cause a constant current draw. I have also seen the voltage regulator and the rectifier in a bad alternator drain some pretty decent current too.
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Old 03-08-2007, 09:24   #3 (permalink)
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Re: Smoking Alternator

I looked over the wiring and connections last night. I can't see anything wrong. Could it be the 4 month old rebuilt alternator has a problem like bad rectifier diodes? Isn't the regulator built right in the alternator? Maybe that is bad.

Since nobody posted anything about a known problem that causes this, I will buy another rebuilt alternator (with lifetime warranty) and bolt it in. This alternator is probably under warranty, but the previous owner of the car bought it.

Any tips on alternator brands to avoid? I'm planning on buying one from Autozone for $140. Autozone has always been good to me with their lifetime warranties. I got a couple free sets of brake pads and a pair of front axles/CV joints for my wife's Subaru at no charge.
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Old 03-08-2007, 12:52   #4 (permalink)
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Re: Smoking Alternator

Most rebuilt alternators are junk. I would look for a new one. Advance sells some reasonable priced. Or there is ALTERNATOR-STARTER-PLUS an eBay store.

Be glad you don't have a Duratec as the alternator on the Vulcan is a piece of cake to change.
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Old 03-08-2007, 17:49   #5 (permalink)
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Re: Smoking Alternator

I agree 100%. New is the way to go.

Im sure another alternator will fix the problem, you probably just ended up with a dud.
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Old 03-09-2007, 10:34   #6 (permalink)
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Re: Smoking Alternator

Whatever alternator you get, make sure they bench test it at the store. I once went through 3 rebuilts before getting one that worked. It will save you a trip if the one you bought is bad out of the box.

Interestingly I just replaced mine on my 1997 3L SOHC at 132K miles. The stock one was still working but was going bad at certain RPM loads. I was actually able to drive it for quite some time that way, but when it wasn't working between 50-70 MPH on the highway I thought I better replace it. I guess that makes me the biggest cheapskate.

Good luck with the swap out.
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Old 03-10-2007, 14:13   #7 (permalink)
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Re: Smoking Alternator

You fellows are hard on rebuilts. Sorry, I have different experiences. What is there to rebuild in an alternator??

1) bearings

2) rectifiers

3) field brushes

There was a time, a long time ago when semiconductor technology was in its genesis where diode failure was too common. But today's diodes have higher voltage ratings along with better high current capacities. Both voltage and heat generated by current flow across the voltage barrier are diode killers. Those conditions are well known and design factors yield high MTBF's.

A diode is most likely to fail either when it is first placed in service or after tens of thousands of opertional hours.

Bearings for todays alternators cost range anywhere from $1.50 to around $3.50. Think of their high quality...... spinning up to 10,000RPM's and lasting for YEARS!

Thanks to great technonlogy the generator of old is gone!

Little current flows in the field. Low field current means high life for the brushes. The stationary armature has no moving parts, nothing to wear out.

If a rebuild alternator makes past the first few miles without failing, most likely it will last for years just as an original would.

Foggy
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Old 03-11-2007, 18:00   #8 (permalink)
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Re: Smoking Alternator

I bought the $140 rebuilt with a lifetime warranty from Autozone. They sell an aftermarket "all new" alternator for $165, but it wasn't in stock and it only has a 2 year warranty. It only took 20 minutes to replace, so if this one fails I can get a new one down the street and it's just another 20 minute job to install.

This is in my 17 year old son's Taurus. He drove it yesterday and today and the alternator is working fine. It's not getting hot enough to cause a fire like the last rebuilt that died after 1500 miles and 4 months. The windings are almost black and still stink with a nasty burned smell. I'll take old stinky back to Autozone tomorrow for my $32 core refund.

I did a few tests with the new alternator. The battery was 12.6 volts before starting. With the engine running, the battery reads 14.8 volts, which seems a tad high. I have a clamp type ammeter that reads DC (most only measure AC current). Right after starting, the current from the alternator output cable was 38 amps. After a few minutes, it dropped to 29 amps and stabilized. Right after starting, the charge current into the battery was about 14 amps. This dropped to about 9 amps. Is it normal for the battery to get about 9 amps of charging current continuously? This seems rather high just to keep the battery at full charge. That much charge current probably overcharges the battery. Maybe the regulator voltage is a little too high, or is 14.8 on the battery normal? I know that 12 volt lead-acid batteries in computer UPS units float charge at 13.8 to 14 volts. They say anything higher will just dry out the battery from outgassing and shorten it's life.

Also, I checked the current draw with the new alternator installed. I just connected my DMM leads from the neg post of the battery to the neg battery terminal lead. It still does the same thing. The car draws about 0.7 amps for a few seconds, then drops to about 0.4 amps for a few more seconds, then drops to about 0.18 amps and stays there. I know that the clock, etc. takes some power, but 0.18 amp seems like too much. The car doesn't have an alarm, everything is factory stock Taurus SE. That current means the car is always using slightly more than 2 watts of power just sitting there. That's probably why it wouldn't start after sitting for 4 days. I guess I'll try the old "pull one fuse at a time" trick to try to track down what is drawing the current.
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Old 03-15-2007, 02:24   #9 (permalink)
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Re: Smoking Alternator

I have also just replaced an alternator in my '01 Taurus. I bought a rebuilt from Auto Zone. I have noticed that there is a smell similar to burning rubber that comes and goes while driving the car. I have checked the belt and it is fine. The duct fan will slow down like it is under a power strain and go back to normal speed, so I have not ruled it out yet....thats a different story.
This started right after I changed the alternator and the smell gets very strong when I stop and put the car in reverse to back into the driveway.
I don't see how changing gear shift positions could cause any difference on the alternator, but as I said this all happened right after changing it.
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Old 03-15-2007, 07:15   #10 (permalink)
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Re: Smoking Alternator

My son noticed the same thing. He told me that he could smell something like burning rubber once in a while. I also looked at the sepentine belt and it was fine. When the alternator started billowing smoke, it kind of smelled like burning rubber or a burned up electric motor.

I also checked my Nissan pickup battery voltage. It is reading 14.05 volts with the engine idling. My son's Taurus is 14.7 to 14.8. That seems a little too high.

The guy at Autozone told me the regulator is mounted on the alternator, but the output voltage is controlled by something else in the car. Does anyone know how this works and how I can test and/or repair it? Maybe the alternators are failing because they are trying to keep the system voltage higher than it needs to be. That would cause the alternator to output a lot more current and get hot.
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