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Overheating Alternator???


cdliwski
02-01-2008, 01:36 PM
After running fine for 15-20 minutes my alternator will begin to heat up until the point where it is too hot to even touch. As the alternator heats up the charge of the battery begins to drop until the point where the battery drains and the car dies. After sitting for enough time for the alternator to completely cool off the car will start up fine, but the process soon repeats itself.

I removed the alternator and had it tested professionally and was told that there were no indicators that pointed to it being a bad alternator. (They did not run it in the test environment for more than 2 minutes however). The leads all appear to be fine and everything is emitting the proper amps until the overheating begins.

Has anyone had a problem like this or have any suggestions as to what next steps I should take?

Thanks.

MalibuBob
02-02-2008, 12:03 PM
Bring it back and have them test it again (or bring it somewhere else), this time running it for however long it takes for this problem to re-occur.
I don't know how much heat an alternator should generate, but anytime the output starts to drop off, you've got a problem.
Are you hearing any noise that may be the bearings going bad?

cdliwski
02-02-2008, 01:59 PM
I just bought and put in a brand new alternator. Within 20 minutes it's again too hot to touch and the battery charge begins to drop. Haven't taken it out for a long drive yet as I don't love getting stranded and waiting for a tow truck.

Do alternators generally give off heat? Any suggestions??????? This sucks...

MalibuBob
02-02-2008, 03:07 PM
Anything under the hood will get somewhat hot due to the heat build-up under from the engine. However, that alone should not be causing a voltage drop.
I'm wondering if you've got a wiring problem after the alternator that is causing an excessive current draw, and causing the rectifiers in the alternator to overheat.
In any event, I sure wouldn't trust this car until you've had it more thoroughly checked, because as it stands now, it will leave you stranded somewhere.
PS, where/how are you measuring the voltage drop? (Just curious).

slls
02-03-2008, 09:53 AM
I just bought and put in a brand new alternator. Within 20 minutes it's again too hot to touch and the battery charge begins to drop. Haven't taken it out for a long drive yet as I don't love getting stranded and waiting for a tow truck.

Do alternators generally give off heat? Any suggestions??????? This sucks...

Yes alternators give off heat, they have an internal fan to cool it. The will get too hot to touch after running a while.
I would test the voltage at the battery with a meter, should be around 12 V.
A good test is at 1500 rpm, headlights, heater fan and radio on, should hold around 14 V.

bfranklin88
08-06-2009, 03:14 PM
I have a 2001 Toyota Sienna with the same issue. I have gone through 4 alternators in a week. Did you find out what was wrong?

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