how to use digi multimeter to test alternator.

[golf73]

1973 standard '02, red charging light is glowing faintly, had the battery tested it's about 90% charged @ around 12.5V.

bought a DMM (yellow INNOVA 3300 from Kragen for $10) but am confused as to which setting to put it at to test alternator output - do i set the knob to DCV to measure volts, right?

not sure which numerical setting to put it at, 200m, 2, 20, 200, or 500?

then there are 3 plugs at the bottom, 2 red and one black, not sure which red jack to use - "DC 10A" or "V ohms mA -> BAT."

after i figure out these settings, i can follow the FAQ charging system by myself.

any help greatly appreciated.

ryan

san fran

[gwb72tii]

20 or 200 vdc will work for the max range. your alternator should be putting out around 13v when the car is running. if its putting out more than about 13.5 max, your voltage regulator is shot. my 2002 needed alternator brushes ($5) some time ago when the alt light was glowing faintly at idle and not glowing at all at higher rpm's. pretty easy fix. 12.5v is a good reading for a battery that's charged with the car off.

the black lead is for the black "common" hole.

put the positive lead in the V ohm connection for measuring volts or resistance.

good luck!

[PatAllen]

20 or 200 vdc will work for the max range. your alternator should be putting out around 13v when the car is running. if its putting out more than about 13.5 max, your voltage regulator is shot. my 2002 needed alternator brushes ($5) some time ago when the alt light was glowing faintly at idle and not glowing at all at higher rpm's. pretty easy fix. 12.5v is a good reading for a battery that's charged with the car off.

the black lead is for the black "common" hole.

put the positive lead in the V ohm connection for measuring volts or resistance.

good luck!

i dont agree 100%, i work in 12v business for the past 20 years, i am aware of several cars that puts out more than 13.5v, i wouldnt recal the regulator to be dead unless it put out more than 15v. Standard charging voltage is 14.4v per sae documents.

My stock 02 back then with its poor designed charging system was making 14.7v "empty" and droped down to 12.9 with head lights on. Regulator was fine, believe me.

What you want to check is not necessary only the voltage but the current output. That is something totaly different and require different task/skills.

[golf73]

thanks gwb72tii, that clears it up for me.

my warning indicator doesn't seem to change in brightness at all when i increase or decrease the RPM's, so i wonder if that means the diodes are shot. is the voltage regulator located on the inside of the front fender next to the battery? if so, it looks like mine's been replaced before with one of brazilian origin.

[golf73]

the FAQ guide says that the voltage regulator is shot if the system voltage at the alternator is >+14.7

[PatAllen]

the FAQ guide says that the voltage regulator is shot if the system voltage at the alternator is >+14.7

yeah, i dont want to shew up my words...14.7-15v...a 10$ multimeter might not have that much precision altought it has that resolution...lol...