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roybelding
roybelding, ASE Master Tech
Category: Mazda
Satisfied Customers: 5717
Experience:  40 years experience ASE master tech
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Have 2001 Tribute, checked battery and alternator with DVM.

Customer Question

Have 2001 Tribute, checked battery and alternator with DVM. No alternator output voltage, Can jump start with portable battery charger. Voltage will rapidly drop from @ 12.75 vdc, to @ 8.85 vdc, then engine will shut down. Alternator is @ 18 months old, kicker is the alternator indicator light never comes on except upon ignition key switching to accessory. Is there a possible problem in the wiring electrical components, the alternator fuses were pulled and tested good with the DVM ( @ 0.4 ohms).
Submitted: 1 year ago.
Category: Mazda
Expert:  roybelding replied 1 year ago.

good morning my name is ***** ***** I will assist

first, nothing will work with 8.85 battery voltage. you need to charge it to 12.6 volts and then re test.

the alternator will work if it can once it has 12 volts to activate it.

lets start there and then re test

Roy

Customer: replied 1 year ago.
If the battery sits without starting vehicle it will build up to @ 11 6 vdc on its own, not enough to start it. Hooking up portable charger will start vehicle. Disconnecting charger will leave battery voltage @ 12.4 to 12.27 vdc, volage will not climb to @ 14.5 vdc at battery terminals. in @ 5 minutes voltage at the battery terminal will start dropping, until it is low enough to kill the engine.
Expert:  roybelding replied 1 year ago.

ok, with the battery being dead, the voltage will not build due to high amperage, if the alternator is working. it sounds like it is not but with a very low battery such as you have the testing is in accurate until your battery is up to voltage.

Roy

Expert:  roybelding replied 1 year ago.

how are you making out

Customer: replied 1 year ago.
going to have the battery tested for damaged cells and load. will be back in @ an hour. what is the expected readings for the diodes, and the positioning? Also are they protective for the charging circiut?
Expert:  roybelding replied 1 year ago.

yes they are. at this point get the battery up to charge and then we will do testing. we will check with volt meter for charging and ripple on the diodes

Roy

Customer: replied 1 year ago.
just returned with battery, tested good, placing it on the charger to build up voltage to @ 12.7 or a little higher.
Expert:  roybelding replied 1 year ago.

ok, run the truck and see what the voltage is at battery

Roy

Customer: replied 1 year ago.
it is charging now, unfortunately it will only run for 5 to 10 minutes.
Expert:  roybelding replied 1 year ago.

what is the voltage???

Customer: replied 1 year ago.
12.71 vdc, charger disconnected. figured on charging to @ 13.00 vdc.
Expert:  roybelding replied 1 year ago.

not good. needs to be 14 to 14.5 volts on dc

switch to ac and see if there is any voltage that will check the diodes.

Roy

Expert:  roybelding replied 1 year ago.

how are you making out

Customer: replied 1 year ago.
diode #1 closest to engine checked to positive 13.874 vdc both sides, checked to negative 0.00 vdc both sides
diode #2 closest to fender checked to positive 1.726 vdc one side 0.128 vdc other side, checked to negative
10.836 vdc both sides.
Expert:  roybelding replied 1 year ago.

please stop measuring diodes. not needed at all.

is the charge rate 13.8 volts dc???

all you need to do to check the diodes is measure ac voltage at the battery. it should be 0 volts. thats all the testing you need to do

Roy

Expert:  roybelding replied 1 year ago.

please dont forget to rate me as it is the only way I get paid for my efforts

Roy