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Thu Jan 07, 2010 1:14 pm

if your alternator is putting out voltage? Is there somewhere to read voltage with a multimeter, or a part of the unit that is magnetized? I'm trying to determine why my battery isn't charging. It takes a charge off of a charger no problem. I'm trying to determine if it's a wiring issue, blown fuse somewhere, or a bad alternator.

Thanks!

Thu Jan 07, 2010 1:19 pm

with the engine running check voltage at the generator/alt. at the b+ side you should have over 13v or so then check voltage at the battery to see if its getting charged from the alt.

do you have a generator or an altinator?

Thu Jan 07, 2010 1:39 pm

Nachodaddy77 wrote: with the engine running check voltage at the generator/alt. at the b+ side you should have over 13v or so then check voltage at the battery to see if its getting charged from the alt.

do you have a generator or an altinator?

I have an alternator. It has the blade-connector and the little threaded post on it- which is b+?

Thu Jan 07, 2010 1:46 pm

Thu Jan 07, 2010 1:59 pm

another item to check is the ground cable / wire make sure they are clean, secure and the proper size.

Thu Jan 07, 2010 2:35 pm

Is your idiot light working?
Some alternators need "exciter voltage" to get started charging. Many systems just use the idiot light for that voltage, and when the bulb burns out, the charging system quits.

Thu Jan 07, 2010 3:20 pm

with the car running, pull the battery cable off, turn on headlights, if car still runs then working.

Thu Jan 07, 2010 3:28 pm

chubby53 wrote: with the car running, pull the battery cable off, turn on headlights, if car still runs then working.

That is very hard on an alternator. It needs the battery as a voltage reference.

Thu Jan 07, 2010 9:05 pm

Russ Wolfe wrote: Is your idiot light working?
Some alternators need "exciter voltage" to get started charging. Many systems just use the idiot light for that voltage, and when the bulb burns out, the charging system quits.

RUSS WOLFE is my hero. Good grief! I bought a flippin' new alternator when I didn't even need it. I had NO IDEA that stupid little light was absolutely ESSENTIAL to the charging system. I found a link to a site that explains in detail how the light works. What I didn't know until I read it was that the speedo illumination lights are the same bulb, so I swapped one of those out and turned on the key, and the idiot light came on. I started the car, and checked the B+ voltage at high idle, and instead of showing battery voltage (12.5 ish), I'm now showing around 14.5V.

Here's the link, if anyone's interested.http://www.vw-resource.com/alternator_wiring.html#alt

Thanks again, Russ!

Thu Jan 07, 2010 9:17 pm

Never disconnect a car battery cable from a vehicle with the engine running, because the battery acts like a filter for the electrical system. Unfiltered (pulsating DC) electricity sometimes exceeding 40 volts is produced by the alternator and can damage electrical components such as audio system, charging system, alarm system, etc.

A charged battery should read above 12.5V.
If your voltage is below 10V it's low on charge
If it won't take a charge, it's shot.
Start the motor, you should be getting 13.5-14.5V

Many toy cars are not run long enough to completly top off a battery charge. The length of time to fully recharge the battery depends on the amount of discharge, the amount of surplus current that is diverted to the battery, how long the engine is run, engine speed, and ambient temperature. An alternator is sized by the vehicle manufacturer to carry the maximum accessory load and to maintain a battery and NOT to recharge a dead battery. For example, if 300 amps were consumed for two seconds to start a car from a fully charged battery, it will take an 80 amp charging system approximately 7.5 seconds to replace the .167 amp hours of power used. If 25 amps are available to recharge the battery, it will take 24 seconds and 10 minutes at one amp. With a dead 60 amp hour battery, it would take approximately 90 minutes at 80 amps, 4.8 hours at 25 amps, or 120 hours at one amp to fully charge (100% State-of-Charge) it. If you left your lights on or drained your battery somehow, you should put it on a charger overnight.

Fri Jan 08, 2010 12:00 am

i've even heard if you get a new battery you should charge it with a charger overnight the first night you get it.

Fri Jan 08, 2010 12:24 am

chubby53 wrote: i've even heard if you get a new battery you should charge it with a charger overnight the first night you get it.

It's not a bad idea. Batteries will self discharge just sitting on the shelf. Look for date codes on batteries and buy the freshest one on the shelf. Batteries need a freshening charge every 3-6 months. I've never seen a rack of batteries get charged in a store, so go for the newest one you can find. A battery kept fully charged will last longer than one that hasn't.

Fri Jan 08, 2010 9:32 am

Quote: Never disconnect a car battery cable from a vehicle with the engine running, because the battery acts like a filter for the electrical system. Unfiltered (pulsating DC) electricity sometimes exceeding 40 volts is produced by the alternator and can damage electrical components such as audio system, charging system, alarm system, etc.

add to this true statement: Use a stiffening capacitor. big round thing with two connections, the size of an Australian beer can. Do not wire it up backwards.

Smooths out spikes. search eBay for audio capacitor or stiffening capacitor. The $20 works just as well as the $200 one.

Without a cap the voltmeter on my Harley looks like a windshield wiper at idle. With a cap, rock steady.