bad diodes in alternator

[94HeavyChevy]

i took my alternator off my 94 caprice 5.7 and had it tested at advanced. came back bad diodes but charged fine. i have a pretty significant draw in the car. any way it can be from the bad diodes in the alternator? should i replace the alternator?

[j cAT]

Originally Posted by 94HeavyChevy

i took my alternator off my 94 caprice 5.7 and had it tested at advanced. came back bad diodes but charged fine. i have a pretty significant draw in the car. any way it can be from the bad diodes in the alternator? should i replace the alternator?

having some bad diodes will cause the headlights to dim when at IDLE ...do the lights at night vary in brightness???

diodes can short out ///this causes the battery to drain when engine is not running..

what test did they say failed...does it have proper output or does the alternator have leakage ...you should have the 140 amp alternator..

why did you have this tested ? what is the problem ?

if you have these problems get a new alternator with the lifetime warrantee..do no get the rebuilt one..

I have seen this alternator go bad on the stator windings..best get new.

[94HeavyChevy]

never really notice lights dimming.

car starts up fine when cold (sitting over night) but after driving then restarting battery charges very slow. battery seems weak(lots of battery bounce when rolling up windows, hitting the brake to shift into gear, turning light on, etc). if i leave car for 3 days the battery will die. i got the alternator tested because a few people told me sometimes they can stay on while the car is off causing the battery to die.
i am definetly going to get a new one. any specific brand i should get i have seen a few different ones.

[j cAT]

Originally Posted by 94HeavyChevy

never really notice lights dimming.

car starts up fine when cold (sitting over night) but after driving then restarting battery charges very slow. battery seems weak(lots of battery bounce when rolling up windows, hitting the brake to shift into gear, turning light on, etc). if i leave car for 3 days the battery will die. i got the alternator tested because a few people told me sometimes they can stay on while the car is off causing the battery to die.
i am definetly going to get a new one. any specific brand i should get i have seen a few different ones.

with those issues I would say they did correctly get the shorted diodes as the problem.

I got a dephi lifetime warrantee alternator at autozone. about 125.00 approx ..

when you replace this alternator put the battery on the charger.don't want a new alternator to put out max current before running for a time ...seating the alt brushes on break in is important for a long life.

[94HeavyChevy]

so i replaced the alternator and no more draw. hooked up a voltmeter to the battery and it stayed strong while the car was off at 12.92.

i do believe i have some sort of short in my dash though. im still getting a ton of battery bounce whenever i roll up or down windows, turn on the vent, hit the brakes, turn on lights or turn on my blinker. But no different charge when doing all these and someone outside the car with a voltmeter hooked to the battery. And the lights do not dim at all when the battery is bouncing which tells me it is just the voltmeter guage on the dash that is messed up. Also my temp guage on the dash bounces when i hit the brakes. Are all of these guages on the cluster individually wired or is it all one connection? Is this something i can fix on my own? Do i need a whole new dash? Can i send it out for repair?

[j cAT]

Originally Posted by 94HeavyChevy

so i replaced the alternator and no more draw. hooked up a voltmeter to the battery and it stayed strong while the car was off at 12.92.

i do believe i have some sort of short in my dash though. im still getting a ton of battery bounce whenever i roll up or down windows, turn on the vent, hit the brakes, turn on lights or turn on my blinker. But no different charge when doing all these and someone outside the car with a voltmeter hooked to the battery. And the lights do not dim at all when the battery is bouncing which tells me it is just the voltmeter guage on the dash that is messed up. Also my temp guage on the dash bounces when i hit the brakes. Are all of these guages on the cluster individually wired or is it all one connection? Is this something i can fix on my own? Do i need a whole new dash? Can i send it out for repair?

the battery and alternator are connected with a large guage wire which has a fuseable link. this is now working correctly and the voltage is solid not varying...

the fused devices in your vehicle however have voltage drop when ever you turn on devices...this can be and maybe the under hood fuse block connection. this is from the battery to the fuse block..

AT THE UNDERHOOD FUSE BLOCK CHECK THAT THIS RED WIRE CONNECTION IS NOT MELTED LOOSE DAMAGED IN ANY WAY.....

measure the fuse voltages put the emergency flashes on ....see if these are varying, measure the voltage at this red feed wire...see whats up !

[Blue Bowtie]

Check the main power node (stud) in the UEC. There was a TSB on the failure of this connection and the damage to the bussing in the UEC as a result. Measuring at the battery with no voltage drop would tend to confirm that.