Does removing the negative battery cable while the cars running test the alternator?
Like if the car stays running it works, if it kills it doesn't.
Heard this from a friend, just wondering if its true.
alternator testing question
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vancouverbc
- Posts: 3197
- Joined: Thu Oct 30, 2003 1:30 am
- Car: 1991 240sx
Re: alternator testing question (gogg)
Alternator test using volt meter:1.turn headlights on for 15-20 seconds to remove surface charge2.measure voltage across battery when engine off3.turn off all electrical loads ie wiper ,etc4.start engine and increase speed to 1500 rpm5.measure voltage across battery with engine steady at 1500 rpmthe voltage reading should be at least .5 volt higher with engine running. if voltage goes up more than 2.5 volts, alternator overcharging.
You can also test with engine running with lights on at 2000 rpm. the voltage should increase at least .5 volts
are your headlights brighter with the engine running? they should be if alt is working.
You can also test with engine running with lights on at 2000 rpm. the voltage should increase at least .5 volts
are your headlights brighter with the engine running? they should be if alt is working.
Re: alternator testing question (vancouverbc)
Ok, tested it. At 1500 rpms it increases about .3 volts. I forgot the exact numbers but it wasn't hitting .5 until about 2000 rpms.vancouverbc wrote:Alternator test using volt meter:1.turn headlights on for 15-20 seconds to remove surface charge2.measure voltage across battery when engine off3.turn off all electrical loads ie wiper ,etc4.start engine and increase speed to 1500 rpm5.measure voltage across battery with engine steady at 1500 rpmthe voltage reading should be at least .5 volt higher with engine running. if voltage goes up more than 2.5 volts, alternator overcharging.
You can also test with engine running with lights on at 2000 rpm. the voltage should increase at least .5 volts
are your headlights brighter with the engine running? they should be if alt is working.
I drove my car for a bit then killed the car and tried starting again. The started started turning slower like it lost power. I took the volt meter and put it on the battery with the key in, 10 volts, when i turn the key to start the starter clicked, and the volts went down to 2, there was a pause, then rapid clicking from the starter. After I let go of the key the battery was down to 8 volts.
Whats going on? Is my starter grounding out on something and draining the battery? Is my alternator up to par? It's one I had lying around and got tested at o'reilly, they said it was good so i popped it on my car.
Re: alternator testing question (gogg)
It sounds like the battery is just really drained...
-Jerome
-Jerome
Re: alternator testing question (JeromeS13)
Keep in mind I put in a fresh recharched battery with a good 12.5 volts at the beginning of my testing.JeromeS13 wrote:It sounds like the battery is just really drained...
-Jerome
Re: alternator testing question (gogg)
Then there's likely something else wrong. If the alternator was tested outside of the car and good, and you installed a fresh battery, something isn't allowing it to charge the battery. Check your big 70 amp fuse (IIRC) in the fusebox behind the battery. Also, double check all of your wiring and belts at the alternator.
-Jerome
-Jerome
I've gotten a new battery, after a couple days of driving it got drained about 1 volt. I'm really starting to think that the .3 volt increase isn't enough. I've re-tested and I keep getitng .3 volts of increase, not .5 volts. So I'm gonna change alternators again. Other things are fishy too, like my wipers, they work really slowly...
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vancouverbc
- Posts: 3197
- Joined: Thu Oct 30, 2003 1:30 am
- Car: 1991 240sx
Re: (gogg)
10. WHAT CAUSES MY BATTERY TO DRAIN OVERNIGHT?Last Updated on May 21, 2007
Parasitic (or ignition key off) drain is the cumulative load produced by electrical devices, for example, emissions computers, clocks, security alarms, radio presets, etc., that operate continuously after the engine is stopped and the ignition key has been switched off. Normal parasitic loads are below 75 milliamps (.075 amps). When the parasitic load is greater than 75 milliamps (.075 amps), batteries will drain more quickly. Glove box, trunk, and under hood lights that do not automatically turn off when the door is closed or shorted diodes in alternators are the most common offenders. Cooling fans, power seat belt retractors, radios and dome lights left on, alarm systems, and electric car antennas have also caused batteries to drain overnight. Leaving your headlights on will generally discharge a fully charged car battery, with 90 minutes of Reserve Capacity (36 amp hours), within a couple of hours.
It is highly recommended, especially if you are using a sealed wet "Maintenance Free" (Ca/Ca) battery, that you allow it to thaw if frozen, fully recharge it in a well ventilated area with an external battery charger, remove the surface charge, and load tested both the battery and the charging system for latent damage from the deep discharge. You could have a damaged or bad battery. If the alternator is warm and the engine is cold, then check for a shorted diode in the alternator.
Below are some methods that are used to test the parasitic load with the engine NOT running, under hood light disconnected, all accessories switched off, and the vehicle doors closed:
Connect a 12-volt bulb across the positive and negative battery terminals to test the bulb and the battery. If it glows brightly, then remove the negative battery cable and connect the bulb in series between the negative battery cable terminal clamp and the negative battery terminal. If the bulb continues to glow brightly, then start removing fuses or connections to the positive battery post one-at-a-time until the offending electrical component is identified by the bulb dimming.
A better approach is to use a DC ammeter, for example a Fluke 175, inserted in series with the negative battery cable terminal clamp and the negative battery terminal or a clamp-on DC ammeter, like a Fluke 336 or i410 around the negative battery cable. Starting with the highest scale, determine the current load. If the load is above 75 milliamps (.075 amps) after the initial surge, then start removing fuses or connections to the positive battery post one-at-a-time until the offending electrical component is identified by the parasitic load dropping to within 75 milliamps (.075 amps).
Additional troubleshooting techniques can be found in a guide from Exide at http://www.exide.com/products/...d.pdf.<<<Previous [Home] [Top] Next>>>
Parasitic (or ignition key off) drain is the cumulative load produced by electrical devices, for example, emissions computers, clocks, security alarms, radio presets, etc., that operate continuously after the engine is stopped and the ignition key has been switched off. Normal parasitic loads are below 75 milliamps (.075 amps). When the parasitic load is greater than 75 milliamps (.075 amps), batteries will drain more quickly. Glove box, trunk, and under hood lights that do not automatically turn off when the door is closed or shorted diodes in alternators are the most common offenders. Cooling fans, power seat belt retractors, radios and dome lights left on, alarm systems, and electric car antennas have also caused batteries to drain overnight. Leaving your headlights on will generally discharge a fully charged car battery, with 90 minutes of Reserve Capacity (36 amp hours), within a couple of hours.
It is highly recommended, especially if you are using a sealed wet "Maintenance Free" (Ca/Ca) battery, that you allow it to thaw if frozen, fully recharge it in a well ventilated area with an external battery charger, remove the surface charge, and load tested both the battery and the charging system for latent damage from the deep discharge. You could have a damaged or bad battery. If the alternator is warm and the engine is cold, then check for a shorted diode in the alternator.
Below are some methods that are used to test the parasitic load with the engine NOT running, under hood light disconnected, all accessories switched off, and the vehicle doors closed:
Connect a 12-volt bulb across the positive and negative battery terminals to test the bulb and the battery. If it glows brightly, then remove the negative battery cable and connect the bulb in series between the negative battery cable terminal clamp and the negative battery terminal. If the bulb continues to glow brightly, then start removing fuses or connections to the positive battery post one-at-a-time until the offending electrical component is identified by the bulb dimming.
A better approach is to use a DC ammeter, for example a Fluke 175, inserted in series with the negative battery cable terminal clamp and the negative battery terminal or a clamp-on DC ammeter, like a Fluke 336 or i410 around the negative battery cable. Starting with the highest scale, determine the current load. If the load is above 75 milliamps (.075 amps) after the initial surge, then start removing fuses or connections to the positive battery post one-at-a-time until the offending electrical component is identified by the parasitic load dropping to within 75 milliamps (.075 amps).
Additional troubleshooting techniques can be found in a guide from Exide at http://www.exide.com/products/...d.pdf.<<<Previous [Home] [Top] Next>>>