Alternator Troubleshooting Trick

**Taurus** · June 4th, 2009 07:28 PM

[SIZE=+2]Warning![/SIZE]
Some people tell you that you can check your alternator by disconnecting it from the battery to see if the alternator can produce enough current to keep the engine running. BAD IDEA! Disconnecting the battery will subject the voltage regulator (and computer and audio equipment...) to significant voltage spikes which may cause an otherwise good alternator to fail. Even if there were no damaging spikes, this test would not indicate whether or not the alternator was good because the engine will easily run with a weak or failing alternator.
Simple Test: If you want to see if your alternator is producing current, turn on your headlights when you're parked and the engine idling with the headlights shining on a wall (at night). Notice how bright they are. Then turn the engine off. The lights should get dimmer when you turn the engine off. If the lights get brighter when you kill the engine, the alternator was not charging sufficiently. When doing this test, the lights should be the only load (turn the stereo, a/c and other accessories off). With a heavy load, an otherwise good alternator may not be able to produce sufficient amounts of current at idle.

**jick.cejoco** · June 5th, 2009 05:58 AM

Originally Posted by joseph20

Mga experts, totoo po ba yung tricks o troubleshooter technique sa alternator na Once na tinnangal yung negative clamp habang umaandar yung auto and then namatay, my sira o may diperensya yung alternator?? Effective po ba iyon. TnX im aDvance

joseph,
there had been discussions on this topic. it is wrong for any "mechanic" to mess with the electrial system and electronic systems associated with it. please request the moderator for the previous discussions on this matter. it is a recurring question that has been anwered in the past. we are regurgitating this again. do not disconnect any battery terminal while the engine is running if you don't want electrical damage or electronic surprises. again, request for previous threads on this.
jick

**max-o** · June 11th, 2009 03:46 PM

just buy a multitester mura lang naman less than 200petot

,pang iwas sa mga siraniko.

**jick.cejoco** · June 11th, 2009 04:57 PM

Originally Posted by max-o

just buy a multitester mura lang naman less than 200petot

,pang iwas sa mga siraniko.

max,
tools don't make a technician. with today's cars you need more than mechanics. you need educated, trained and experienced technicians with the proper tools and equipment, with the proper knowledge, diagnostic skills and repair skills. i wish it was all that easy as you make it sound like. let us keep learning and keeping up with the transportation industry
jick

**alwayz_yummy** · June 11th, 2009 05:20 PM

basta sa multi tester, while the engine is not running, voltage on the terminals of the battery should be atleast 11.1V

while the engine is running, it should be 12.1V-14.5V depending sa loading(buhay na accessories)

if below 12V, di na kumakarga ng maganda ang alternator...madidischarge na battery mo.pagawa mo na yan!

if above 14.5V alternator mo--sisirain nyan battery mo, worst case--sumabog. maaring sira na ung regulator/IC-regulator ng alternator mo.

**max-o** · June 12th, 2009 04:05 PM

Originally Posted by jick.cejoco

max,
tools don't make a technician. with today's cars you need more than mechanics. you need educated, trained and experienced technicians with the proper tools and equipment, with the proper knowledge, diagnostic skills and repair skills. i wish it was all that easy as you make it sound like. let us keep learning and keeping up with the transportation industry
jick

jick,
been doing that to avoid those inexpereinced technicians

.my digital tester

helps a lot when it comes to battery/alternator problems,at least i know which of the two is busted.

**oj88** · June 12th, 2009 07:33 PM

The battery is like a giant capacitor that helps the alternator supply the car's electronics and accessories with filtered DC current. Disconnecting the battery while the engine is still running will introduce pulsating DC to the electrical system. And since modern cars are highly dependent on a filtered supply of DC, it can affect the ECM/PCM logic, sensors, etc. Problems can range from being temporary (ie. the engine shuts down) to something permanent (ie. weakest link in the chain of semiconductors bites the dust).

The way I test it is to take the baseline voltage of the battery with the engine turned off and comparing it later with a sample battery voltage while the engine is running. Then further take voltage tests with the accessories and lights working. And finally, rev it a few times and see if the regulator is working by observing the output of the voltmeter.

**padek** · July 5th, 2009 02:15 PM

Originally Posted by bambino

to find out if the battery is good:

cranking test
ign coil HT wire grounded

votlmeter hooked up

crank continuously for 30 seconds

while cranking , batt reading should be at least 9.6 V

less than 9.6V = no good

panu po sa avanza ngvibrate ung engine pagka start sa umaga? tapos, mabaho ung usok

**lloydwena** · October 17th, 2009 11:10 PM

mga sir, ano pa dpat gawin, pag na matay ang kotse dahil low battery or na sira alternator?

**yope07** · October 25th, 2009 09:11 PM

Originally Posted by Taurus

[SIZE=+2]Warning![/SIZE]
Some people tell you that you can check your alternator by disconnecting it from the battery to see if the alternator can produce enough current to keep the engine running. BAD IDEA! Disconnecting the battery will subject the voltage regulator (and computer and audio equipment...) to significant voltage spikes which may cause an otherwise good alternator to fail. Even if there were no damaging spikes, this test would not indicate whether or not the alternator was good because the engine will easily run with a weak or failing alternator.
Simple Test: If you want to see if your alternator is producing current, turn on your headlights when you're parked and the engine idling with the headlights shining on a wall (at night). Notice how bright they are. Then turn the engine off. The lights should get dimmer when you turn the engine off. If the lights get brighter when you kill the engine, the alternator was not charging sufficiently. When doing this test, the lights should be the only load (turn the stereo, a/c and other accessories off). With a heavy load, an otherwise good alternator may not be able to produce sufficient amounts of current at idle.

my ride (civic vti a/t) was also a victim of the typhoon ondoy. had the engine fixed na and other electrical wirings. at first maingay yung bearings ng alternator so what i did is change the bearings so ok nawala yung ingay. after 1 week, nagloko yung kotse, minsan ayaw magstart. tick sound lang. after a few times, magstart siya. so pinacheck ko yung starter sa electrician. so ok nagstart. after ilang days ulit, ganoon na naman. tick sound ulit. by the way reduction starter ito. so ginawa nung electrician tinesting ulit, nirekta sa battery nila at gumagana naman. so walang prob ang starter. naisip ko baka alternator ang prob. so sinunod ko itong troubleshoot na ito, naging dimmer naman ang headlyts pag off ko ng engine. DOES IT MEAN NA YUNG BATTERY KO NA ANG MAY PROBLEM>? HELP mga gurus.