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Alternator Check


TOM498's Avatar
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05-16-05, 09:35 AM   #1  
TOM498
Alternator Check

Is there an easy way to tell if an alternator is going bad? I have an '01 Eclispe which seems to be having some mysterious electrical issues. The auto door locks stopped locking from the remote (have to push the lock or use the key to lock). If the lock button is pressed on the inside, the locks lock then unlock. Had 1 instance where the car had to be jumped to start it, but only once. Can I stick a multi-meter on the alternator to check the output, and if so, what should I be seeing. I would guess something over 12 v at idle and probably something over 13 v with the engine at higher rpm. Would the lock problem relate to a bad alternator, or am I looking at 2 separate problems?

Thanks

 
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05-16-05, 03:16 PM   #2  
The lock problem is not related to the alternator. If you have a door ajar light, does it ever stay on? Are all doors and rear hatch closed tightly?

To check the alternator, put the leads on the battery posts or cable clamps and you should get about 13.5 to 14.5 volts anytime the engine is running. If the headlights are dimmer than normal when driving, the alternator is suspect.

 
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05-17-05, 06:52 AM   #3  
TOM498
Thanks Jeff67.

 
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05-17-05, 08:54 AM   #4  
While the engine is running take the negative battery cable off the battery, if the engine dies then there is no current comming from the alternator. If you have a voltmeter just use it, if you don't have a volt meter go buy a cheap one at the parts store. If your gona be DIYin then you will need one anyway.

 
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05-18-05, 05:19 AM   #5  
hate to disagree with you...

...but removing the negative battery cable while the engine is running is very dangerous on computerized vehicles. it can easily cause voltage spikes that toast electronic modules. some modules, esp asian ones, can be VERY expensive.

 
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05-18-05, 06:26 AM   #6  
whatever

whatever your book says! I have never had a problem removing cables, ever heard of a REGULATOR. FUSE ECT.

 
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05-18-05, 06:29 AM   #7  
just trying to help...

...please don't be offended.

 
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05-18-05, 09:12 AM   #8  
The two provblems mentioned in the original post are not related.

The best way to see if it's the alternator is to install a voltmeter and watch the voltage when you drive around. Generally speaking, measure the voltage with the car off. Then start the car and check the voltage again. If voltage is higher, alternator is good. If lower then it's bad. Understand.

Do NOT remove the negative battery cable when the car is running unless you want to fry most of the electronics in your car. That was only OK to do in cars make up to sometime in the 1970's.

 
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