how to check alternator?

[DavidT]

My sho recently started to behave a little differently every time I start it. It WILL start every time, just NOW it seems to maybe crank a tad slower. I can invision it just coming to a complete STOP during the cranking.
I am wondering if its the battery or the alternator or maybe the starter. I was wanting to test some or all of the suspects before I get stranded somewhere...

 

[wood_e]

AutoZone can test all of them for you

 

[Ian Macoomb]

You can do a basic test with a voltmeter or a multimeter set to DC volts. Check the voltage with the car off. It should read around 12.6 volts. With the car running the voltage should be 13.6-14.4 volts. Then you could add a bunch of load to the system. Turn on the lights, the hazard lights, the climate control fan to high, the rear window defroster, etc. Then check the voltage, it may drop a bit at idle but it should still be in the 13 volt range or better.

 

[DavidT]

battery results:

12.09 OFF
13.15 car running (no accessories)
12.13 car running (all accessories)

Seem OK? I know these are a little low for what Ian said. Too low?

 

[Ian Macoomb]

battery results:

12.09 OFF
13.15 car running (no accessories)
12.13 car running (all accessories)

Seem OK? I know these are a little low for what Ian said. Too low?

I just checked my own car and this is what I got:

12.72 off (car had been run 5 minutes prior so there was some residual charge)
12.67 off after I put the headlights on for 20 seconds
13.54 at idle (with daytime running lights on though)
12.25 with everything I could think off turn on

I'm thinking that my alternator isn't doing so well. I'd expect higher numbers with the loads on. Perhaps the high underhood heat effects the output. Perhaps it doesn't put out enough at idle. I'd like to try upping the revs to 2000 rpm with the full load on to see if the voltage goes up. I would imagine it would but there was nobody around to help me.

Anyway, I think your battery may be weak. The car off voltage seems to show that. The idle voltage is low too but that could be because the dying battery is drawing a lot of current from the alternator in attempt to recharge it. You could also have a bad voltage regulator inside the alternator.

 

[DavidT]

thanks for the info. Turns out it WAS the battery.

 

[JSIL1]

thanks for the info. Turns out it WAS the battery.

Get an odyssey, either the 925 or the 1200 great quality

 

[cmichaelo]

Get an odyssey, either the 925 or the 1200 great quality

Joshua,

Where did you buy your Odyssey and how much did you pay?

Did you get it with or without metal jacket?

And finally, how did you mount it?

Btw, it would seem that the no-load output of an Odyssey battery is somewhat higher than that of a lead-acid battery. Odyssey claims 12.84V. Lead-acid is 12.64V.

Michael

 

[SHOZ123]

I got my PC 925 Odyssey from www.batteries4everything.com The metal jacket isn't needed. The best setup if you are into lighter weight when racing would be two PC 680s in parallel. Then when racing take one out.

 

[JSIL1]

Joshua,

Where did you buy your Odyssey and how much did you pay?

Did you get it with or without metal jacket?

And finally, how did you mount it?

Btw, it would seem that the no-load output of an Odyssey battery is somewhat higher than that of a lead-acid battery. Odyssey claims 12.84V. Lead-acid is 12.64V.

Michael

I got it from the same place Paul did and paid it think $133, I ordered it w/o the metal jacket, and it came to me with a broken termianl so then they sent me a new one with the jacket. check out page 5 on my website for how i mounted it.