Does alternator voltage drop below 14v?

[but]

So my battery tested bad,and I replaced it with a new one,so im hunting down to see if it was just a bad battery or my alternator isnt charging,I first started it up and measured the voltage,and got a 14.65 wich is perfectly fine. I drive around and stop at the gas station to take the voltage reading again,and it reads 12.09. I drive home and take it ones last time before I turn it off,and it reads 13.46.

Does the alternator just charge when it gets too low? because I always thought it had to be 13+ volts.

Also where can I buy an OEM alternator as this is my second napa reman alternator.

 

[Colt4G63 also]

You thought right, it shouldn't get that low. I would check all your connections and your belt tension before you buy a new alternator. You also might want to make sure the harmonic balancer isn't slipping, and of course that there's no fluids getting on the belt.

 

[Burnett03]

An alternator charges non stop as long as the car is running. 14.4 volts is where it should be but most dsm alternators suck and don't charge that well.

 

[but]

Ok thanks guys.


Would a too tight of belt cause this as well? I tightened my belt pretty tight to get rid of the belt squeel when I utilized my heater,so I wonder if it's too tight.

 

[MrP]

You should get a clamp meter and measure the output amps of the alternator, also check what the draw is from your fans stereo etc. Possibly there is a bad diode in the alternator could cause okay floating voltage (14v) but the alternators amperage output would not be able to keep up when hot or under a load especially at idle.

 

[LiquidX]

It's a common thing to happen with non OEM alternators for multiple reasons. Cheaper parts, high heat from turbo assembly, power steering fluid, etc. I'm on my 4th Autozone alternator right now and it was dropping voltage output at idle.

For belt tension you don't want to be able to twist the belt more than 45* which is actually a good belt tension.

 

[but]

So just clamp my postive to the connection of the alt,and then negative to the battery while running? what should the voltage be there?

It's a common thing to happen with non OEM alternators for multiple reasons. Cheaper parts, high heat from turbo assembly, power steering fluid, etc. I'm on my 4th Autozone alternator right now and it was dropping voltage output at idle.

For belt tension you don't want to be able to twist the belt more than 45* which is actually a good belt tension.

I'm most likely just going to get an OEM if I can find one online. Is it ok to use heat wrap to cover it like you would a turbo? I dont have the lower heat shield anymore. I'm pretty sure I have NO power seteering leaks as the alt is clean,but the heat wrap might prevent that also if I do have an unoticable leak.

 

[rabenne]

Depends on where your talking about putting the negative, the battery + or ground would change your reading greatly. if you test it to battery power you will be testing the resistance in the circuit from your alternator to your battery. this is a good thing to check, but I dont believe it will help you find your issue. If you test with your pos on the alt and neg on the battery neg you should be reading anywhere from 13.7-14.4 with no electrical loads on in the vehicle (stereo, heater, etc.). I can help you pinpoint your problem, so dont just go buy an alternator okay!? Could be a problem with the control side of the alternator circuit, and its worth testing if you have the time/patience/tools/and know how.

 

[but]

It just sucks,as this is my second alternator in 3 months,and I cant imagine what would kill them that fast. The guy at the store said its not uncommon to have people defect theirs out more than twice,and thats for regular cars.

What do you mean by "control side?"

 

[LiquidX]

I honestly wouldn't cover it. The slots along the body of the alternator are for ventilation to keep the heat out of there. I would assume that covering it on a DD anyway would end up over heating the alternator. You would be better off putting a blanket on the turbo and any other exhaust parts that are next to it.

Or just go OEM. I'm just going to suck it up since it's lifetime warranty and free to replace.

 

[but]

Is it possible to get an oem one from online or do I have to go to the dealer?

 

[Colt4G63 also]

OEM one online. It is a Mitsubishi Dealer though: Mitsubishi Parts, Up to 70 % Off - Discount OEM Factory Direct Wholesale Mitsubishi Parts Warehouse

 

[but]

Thanks for all the help guys!

 

[rabenne]

What I meant by the control side is the small connector on the alternator. Something has to energize that circuit or the alternator only puts out tiny amount of energy. when you are reading only 12.x volts you are only seeing the available battery voltage, which means the alternator may have lost its "energize" signal. if the problem lies in that part of the charging circuit, an alternator wont fix it. Like I said its worth checking... When the car isnt putting out good charging voltage, probe the wires on the small alternator plug. if it doesnt have battery voltage at that connector, Id focus on why

 

[Steve91]

Hey guys I know this thread is older but I had a question, if my alternator is putting out 15.1 volts even just at idle can that cause some electronics in the car to freak out?

 

[luv2rallye]

No - all systems can handle at least 20v, usually even 25v for that very case of too high alt output.

 

[Steve91]

Ok thank you, it just seems ever since I swapped from a oem alternator I have had some weird electrical problems, just trying to track down the source