alternator

968 · **alternator**

i posted a thread a while back about my engine not running right since i had it detailed. it's been almost three weeks and my symptoms are not improved. i've cleaned every ground point in the engine/body, changed spark plugs, coil packs, every single electrical connection around the engine, MAF, intake, PVC.
i had a mechanic recommend that i check the alternator. it makes sense since is the very first thing at the top front of the engine. i had it tested at two different stores and it checked okay. however, i was reading the test results tonight and they say that it's kicking out 13.8V when unloaded and 13.5V when loaded. the mechanic said that the car works best around 14.4V, but needs at least 14V for the coil packs to fire correctly.

does anyone know if it's possible to pass the alternator test with an alternator that isn't really working properly?

is it possible to clean/freshen up an alternator w/o buying another one?

Otlaw80 · **Re: alternator**

I've never heard that, and quite frankly i call BS. I've tested many altenators from cars from the 60's and 70's through brand new ones with a couple thousand miles. OHV engines, SOHC, DOHC etc. More often than not they put out less than 14 volts without any ill side affects. But not all cars are the same, so...? There are places that can rebuild your altenator for about half the price of a new one, or less. I suppose its worth a shot, but i wouldn't hold my breath.

968 · **Re: alternator**

i saw that they have "high performance" 150 amp alternators available for our mustangs. does anyone have experience with a high amperage alternator? pros/cons? it's expensive - about twice as much as a rebuilt one.

**Herbstang** · **Re: alternator**


Quote: Originally Posted by 968 i posted a thread a while back about my engine not running right since i had it detailed. it's been almost three weeks and my symptoms are not improved. i've cleaned every ground point in the engine/body, changed spark plugs, coil packs, every single electrical connection around the engine, MAF, intake, PVC. i had a mechanic recommend that i check the alternator. it makes sense since is the very first thing at the top front of the engine. i had it tested at two different stores and it checked okay. however, i was reading the test results tonight and they say that it's kicking out 13.8V when unloaded and 13.5V when loaded. the mechanic said that the car works best around 14.4V, but needs at least 14V for the coil packs to fire correctly. does anyone know if it's possible to pass the alternator test with an alternator that isn't really working properly? is it possible to clean/freshen up an alternator w/o buying another one?

Get or borrow a multimeter set to DC volts.
Connect the red meter probe to the positive terminal of the battery (red wire) and the black probe to the negative terminal. If you get it reversed nothing will be damaged, you'll just see a minus sign on the meter's LCD panel in front of the voltage reading. If you have the polarity correct it will be a plus sign. Either way you want to see more than 13 volts with engine running. A fully charged battery will show a little over 12 volts with the engine off.

This may help The Charging System - Part 2: The Alternator

jimmy_beaner · **Re: alternator**

/\ Tis true. My brother's alternator just failed on him.

Battery with car off: 12.0V
Battery reading at idle: 10.9V
Battery Reading with new alternator: 14.4V

968 · **Re: alternator**

i just checked at idle, 14.2V. that seems pretty ideal to me. with the car off, i'm getting right around 12.0V.
i guess the qustion is how it responds under load.

Otlaw80 · **Re: alternator**

need to check the amperage output as well. You can have an altenator that puts out 14 volts and still be bad cause it doesn't put out the right amps.