Charging problem

**jick.cejoco** · February 19th, 2016 03:23 PM

kung shorted ang isa man lang sa mga diode or lahat ng diode, magchcharge pa rin ito right?

if one of the eight diodes is shorted, the fuse blows. your alternator has a Y stator with the neutral point used. check the field coil for resistance. also, check your field coil for current draw while out of the alternator. to do this, connect an ammeter in series with a fused wire. the fuse must be the same amperage rating that of the fuse that goes to the field coil. if the fuse blows, the field coil may be shorted. when you do this procedure, make it quick to prevent polarizing the field coil rotor.

**miked** · February 19th, 2016 03:29 PM

Originally Posted by jick.cejoco

try using a digital multimeter. in diode check mode,
forward bias should read approximately 5v
reverse bias should read OL or infinity

if reading/s are off even on one diode out of the rectifier bridge, the rectifier bridge assembly is shorted.

let me correct myself on some of my errors sir.

studied the diagram of the charging circuit and i was able to separate the rectifier diodes (ac to dc) from the diode trio (for voltage regulation). the diode trio for volt regulation all reads approximately 480 ohms and 1240 ohms. so i assume they are good.

the rectifier diodes are similar to the one on the left on this pic borrowed from the internet: Auto Rectifier, Alternator Rectifier Diode, Automobile Diode, Press fit Diode, Avalanche Diode manufacturer ......mas maliit nga lang.

did some continuity test on the rectifier diodes. the 3 diodes connected to the "B" (charging) terminal all reads the same even with the test leads reversed. continuity on both sides. while the "negative/ground" side diode pack reads 446 ohms and infinity (OL).

am i lucky? but what are the odds of these 3 diodes fail at the same time?

**miked** · February 19th, 2016 03:38 PM

Originally Posted by jick.cejoco

kung shorted ang isa man lang sa mga diode or lahat ng diode, magchcharge pa rin ito right?

if one of the eight diodes is shorted, the fuse blows. your alternator has a Y stator with the neutral point used. check the field coil for resistance. also, check your field coil for current draw while out of the alternator. to do this, connect an ammeter in series with a fused wire. the fuse must be the same amperage rating that of the fuse that goes to the field coil. if the fuse blows, the field coil may be shorted. when you do this procedure, make it quick to prevent polarizing the field coil rotor.

as posted on one of my replies, the 15 amp fuse connected to the charging circuits blows. that could be it.

field coil has zero ohms on all three terminals. no short to ground (or core).

regarding the field coil current draw test, i dont have an ammeter for now. not sure if the 10amps on my dmm will withstand the draw. i think i'll pass on this. baka mamickey mouse ko pa itong alternator.

**jick.cejoco** · February 19th, 2016 03:38 PM

488 ohms tapos 1238 ohm with the test leads reversed. bawat isa sa tatlong diode ganyan ang reading. hindi ba dapat zero ohms tapos infinity?

0 on forward bias and infinity on reverse bias is only available on analog (needle type) multimeter

**jick.cejoco** · February 19th, 2016 03:45 PM

"field coil has zero ohms on all three terminals. no short to ground (or core)."

the field coil is the rotating part of the alternator. the one you mentioned having three terminals is the stator.
your alternator should have four terminals. the fourth one being the neutral point (four wires ganged and soldered together) that goes to one of the terminals of the rectifier bridge

**miked** · February 19th, 2016 06:10 PM

Originally Posted by jick.cejoco

"field coil has zero ohms on all three terminals. no short to ground (or core)."

the field coil is the rotating part of the alternator. the one you mentioned having three terminals is the stator.
your alternator should have four terminals. the fourth one being the neutral point (four wires ganged and soldered together) that goes to one of the terminals of the rectifier bridge

i stand corrected.....yes i mean the stator.

btw, compared the readings of the questionable rectifier diodes to a brand new one. new part reads zero and infinity. the part in question reads continuity both ways.

**Flipo** · February 19th, 2016 06:22 PM

Originally Posted by miked

i stand corrected.....yes i mean the stator.

btw, compared the readings of the questionable rectifier diodes to a brand new one. new part reads zero and infinity. the part in question reads continuity both ways.

definitely damage na; not completely shorted or may leakage na, if disconnected from the circuitry.

**jick.cejoco** · February 19th, 2016 06:26 PM

if one of the eight diodes in negative side of the rectifier is shorted, the fuse blows.

**miked** · February 19th, 2016 09:15 PM

naayos ko rin. katatapos lang. madumi pa nga kamay ko as of this writing:bwahaha:

isang diode lang sa positive side ang shorted. biruin nyo isa lang, anlaki na ng problema.

total damage:

1. Rectifier assembly P1,040.00
2. Carbon brush P25.00
3. Oil seal P80
4. Experience: priceless

another lesson learned....wag iassume na iisang problema lang at test every part.

**Flipo** · February 20th, 2016 01:06 PM

Originally Posted by miked

naayos ko rin. katatapos lang. madumi pa nga kamay ko as of this writing:bwahaha:

isang diode lang sa positive side ang shorted. biruin nyo isa lang, anlaki na ng problema.

total damage:

1. Rectifier assembly P1,040.00
2. Carbon brush P25.00
3. Oil seal P80
4. Experience: priceless

another lesson learned....wag iassume na iisang problema lang at test every part.

Good to know you have sorted it!