Is my alternator broken ?

[kikoteng]

Hi All !

Ride is a corolla xl lovelife. Carb type engine. Headlight bulbs are 100w/90w.

Anyway, last week, car was ok, went to office and parked car.

When I left work and started the car, the car idled very roughly with no lights / aircon / radio on. When I turned on the headlights, it idled even rougher.

I thought the rough idling would go away as the engine warmed but it stayed rough during the full 1-hour drive home.


Next day, cleaned the sparks, and car idled better. Rough idling only when lights on / aircon on / or both on.




Checked the battery voltages:

With engine off - 12.6V
With engine on, no load - 14.3V
With engine on, head lights on - 13.3V
With engine on, aircon on - 13.4V
With engine on, aircon and headlights on - 12.3V




I suspected a battery problems since battery was already more than 2 years old.


Changed to a new battery 2 days ago and got the same voltages (give or take .1 to .2 volts).

Question is :

1. From the voltage readings, does it look there i have a problem with my alternator?

2. Are there other suspects for the rough idling ? Carburetor maybe ?



Thanks in advance for any info guys !

[rmpmla]

baka hindi gumagana yung idle up mo when A/C "on" kaya rough idle.

also, try revving up the engine and see if the voltage goes up based on your previous readings (with loads). pag hindi yan tumaas pwedeng may problem din alternator.

[kikoteng]

Idle up works when AC is on ... I can hear engine increase RPM.

I've also tried increasing idle RPM screw about half or 3/4 of a turn, acceleration is better, less rough idle. But i cant figure out why it suddenly had rough idle without adjusting the idle screws.

BTW, after adjusting the idle screws, voltage is about the same.

Tried revving up the engine (with lights and aircon) . voltage goes up temporarily but goes back down.


Thanks for your insight.

baka hindi gumagana yung idle up mo when A/C "on" kaya rough idle.

also, try revving up the engine and see if the voltage goes up based on your previous readings (with loads). pag hindi yan tumaas pwedeng may problem din alternator.

[jick.cejoco]

the problem statement focuses on the charging system but the real problem is in poor engine performance. typical to these aging cars are bad ignition output. you might consider doing a tune up and check the secondary side of the ignition to include: ignition coil output/high voltage leak, spark plug wire age and resistance, ignition rotor for high voltage leak signs, spark plug condition.

[bambino]

with headlights and AC on try a steady 1500rpm. if the charging voltage remains below 13v suspect the alternator.

most common problems are rectifier assy or stator burnt out

[kikoteng]

You're right. I didnt think to check the ignition coil, etc.

Spark plugs are new though. About 3 weeks. Spark plug wires about 6 months old.

Thanks.

the problem statement focuses on the charging system but the real problem is in poor engine performance. typical to these aging cars are bad ignition output. you might consider doing a tune up and check the secondary side of the ignition to include: ignition coil output/high voltage leak, spark plug wire age and resistance, ignition rotor for high voltage leak signs, spark plug condition.

[kikoteng]

If I step on the gas and rev it up, I'm sure the voltage goes above 13 but goes back down slowly once I let it idle.

Not sure if it reaches 1500 rpm though since the car doesnt have a tachometer.


Re common problems, how does an auto electrical shop check the rectifier assy or stator ?

I've been to one, and what they did was to get a VOM and test the voltage during engine off, engine on idle and with load like what I did. After that, they declared alternator OK. Would that be sufficient ?

Thanks.

with headlights and AC on try a steady 1500rpm. if the charging voltage remains below 13v suspect the alternator.

most common problems are rectifier assy or stator burnt out

[desert fox]

Hi All !

Ride is a corolla xl lovelife. Carb type engine. Headlight bulbs are 100w/90w.

Anyway, last week, car was ok, went to office and parked car.

When I left work and started the car, the car idled very roughly with no lights / aircon / radio on. When I turned on the headlights, it idled even rougher.

I thought the rough idling would go away as the engine warmed but it stayed rough during the full 1-hour drive home.


Next day, cleaned the sparks, and car idled better. Rough idling only when lights on / aircon on / or both on.




Checked the battery voltages:

With engine off - 12.6V
With engine on, no load - 14.3V
With engine on, head lights on - 13.3V
With engine on, aircon on - 13.4V
With engine on, aircon and headlights on - 12.3V




I suspected a battery problems since battery was already more than 2 years old.


Changed to a new battery 2 days ago and got the same voltages (give or take .1 to .2 volts).

Question is :

1. From the voltage readings, does it look there i have a problem with my alternator?

2. Are there other suspects for the rough idling ? Carburetor maybe ?



Thanks in advance for any info guys !

check mo mga belts baka medyo maluwag lang.

[bambino]

^^at idle, you must get at least 13v with headlights and AC on. to test
a rectifier assy ,i use a multimeter set at a diode range but it has to be out of the car.

to test a stator , visually check if its burnt out. set the multimeter at 10k range
check for short to ground and sweep test all four leads for continuity at 100 ohm setting.

there is an easy way of telling if the alternator is on its way out. with the engine running at idle all loads on , you hear a growling noise coming from it .that indicates your stator or rectifier assy is gone.

the hard way ,but its still easy, you have to take the alt out and open the back cover . now you will be able to test these parts.

i assume that you have a little bit of hands on , otherwise you have to bring that to an alternator shop for bench testing.

[kikoteng]

Good point !

Didnt think of that. Will add that one to checklist.

Thanks.

check mo mga belts baka medyo maluwag lang.