New member need some help please

[Jason Gourlie]

I just purchased an 02 4x4 and thanks to this board I have been fixing all the things wrong with it eg....pcv elbow....



but I have a weird issue that just popped up and am hoping for some advice:

my alternator warning light has come on!



Voltmeter on dash shows battery is holding charge,

Voltmeter on battery shows 14.2 with truck running.

Battery has been tested and shows good cranking amps.

Guy at parts store says alternator appears to be ok.



any suggestions on how to get the light to turn off??

 

[RON LAPOINTE]

Ok I got 14.65v on high idle down to 14.4 after warmed up at around 7-800 rpms

 

[Art Garcia]

you sure its an 02. im pretty sure the gauges on the 02's did not have an instrument panel where it indicated stuff such as that. now they change in 03 and those will indicate things like that

 

[Steve McKellop]

Voltmeter on dash shows battery is holding charge,

Voltmeter on battery shows 14.2 with truck running.

Be sure to check all of the connections.



Generally what you describe indicates a possible bad diode in the alternator. It still charges, at a reduced rate, but the indicator make you nervous LOL !! If the parts house is only reading output they are missing the bad diode trio. If one of the diodes fails, it may cause the charging system indicator light to glow dimly. If two or more diodes fail, the light will get brighter. At the same time, the feedback current from the diode trio will reduce the alternators ability to produce current. So the more diodes that fail, the less power the alternator will generate.



To test "diode trio" for damage:



Start the engine and turn on headlights, wiper motor, flashers, etc. to create a "load". Use a digital voltmeter to compare the voltage at the D+ terminal to the voltage at the B+ terminal. The "diode trio" is bad if the voltage at the D+ terminal is not within 0.2 - 0.3 volts of the B+ terminal reading.

 

[David Ponder]

:welcome:





Welcome Jason!!!

 

[Jason Gourlie]

Steve that sounds exactly like the problem...I will do that test....but yes the light is on dimly....is it possible to leave it till another diode fails?



also is this something that I could fix myself??



They want $250 for a new alternator and I am not too keen on spending that right now.



All help is appreciated and thanks for the welcome Dave

 

[Les]

also is this something that I could fix myself??

Find a local rebuilder, he should be able to repair it.