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2000 chevyk3500 6.5l turbo diesel. Going through alternators every month..HELP

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ARwaid

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As you read before, my truck keeps chewing and spitting out alternators, this is my 5th alternator in the last 5months. When I put the new alternator in it will run at about 14.5-15volts, over the next couple weeks it will start to fluctuate from 9 to 15 then eventually die. I have 2 brand new DURALAST PLATINUM AGM batteries and a refurbished 130amp alternator with a lifetime warranty. My auto provider cannot accept the warranty anymore because its obviously not the alternator, its my truck. I am stumped!!! Someone suggested engine ground, or engine to chassis ground??
When the auto store teats my alternator, they say my diodes are going bad. Any ideas??
 
Welcome!

I usually get more than 30 days out of an Autozone alternator. However, I don't shop there due to no-quality parts. The last one died with lots of smoke from a bearing missing it's balls. Autozone is also missing their balls after firing a 'hero' for stopping a store robbery.

I would separate, electrically by removing the grounds, the batteries and test them separately. Leave them separated overnight and any that are under 12.6v in the morning are bad.

Alternators are not rated to charge dead batteries. So if the truck ran awhile without a working alt then the batts become low. AGM batteries will charge at a faster rate and suck lots of current. This overheats the diodes. Failure can show up the next day - it doesn't always show up instantly. I have done this diode cook off with the older CS130 alts and a single low charge AGM bat.

Jump starting can hurt an alternator. If you touch the cables to verify a spark you miss the spark in the now dead alternator... Bad battery chargers also can cook one off.

I would check grounds, battery cable condition including looking for stiff internally corroded cables, and all connections. Especially the alternator charge wire back to the main junction or battery (wherever your model year runs it). A loose (corroded or intermittent) connection can suddenly unload an alternator causing voltages to go sky high and blow diodes. Never remove the batteries from a running engine for this reason. A short from any of the large positive wires could also pop diodes.

High sustained electrical load can also cause this. Any aftermarket electrical stuff?
 
WarWagon said:
Welcome!

I usually get more than 30 days out of an Autozone alternator. However, I don't shop there due to no-quality parts. The last one died with lots of smoke from a bearing missing it's balls. Autozone is also missing their balls after firing a 'hero' for stopping a store robbery.

I would separate, electrically by removing the grounds, the batteries and test them separately. Leave them separated overnight and any that are under 12.6v in the morning are bad.

Alternators are not rated to charge dead batteries. So if the truck ran awhile without a working alt then the batts become low. AGM batteries will charge at a faster rate and suck lots of current. This overheats the diodes. Failure can show up the next day - it doesn't always show up instantly. I have done this diode cook off with the older CS130 alts and a single low charge AGM bat.

Jump starting can hurt an alternator. If you touch the cables to verify a spark you miss the spark in the now dead alternator... Bad battery chargers also can cook one off.

I would check grounds, battery cable condition including looking for stiff internally corroded cables, and all connections. Especially the alternator charge wire back to the main junction or battery (wherever your model year runs it). A loose (corroded or intermittent) connection can suddenly unload an alternator causing voltages to go sky high and blow diodes. Never remove the batteries from a running engine for this reason. A short from any of the large positive wires could also pop diodes.

High sustained electrical load can also cause this. Any aftermarket electrical stuff?
Click to expand...




Thank you sir for your reply!
Nothing aftermaket electrically. These batteries are just fine, I have seperated and left them and they held their charge. The alternators are not from AutoZone, they are from a auto store in the Oregon area called Knechts. They are all refurbished alternators with lifetime warranties.
 
I would get a NEW (not rebuilt/refurb) alternator if buying from part stores.

If you want rebuilt, find a local shop and buy rebuilt from them, instead.

For a 2000, you can get a new AD244 alternator, if you have not done so.
They are rated at 140 amps or so.
This alt is in larger diameter casing.

IMHO.

I bought a new alternator from AZ dot com and it was sent directly from Remy.
So, I suspect, I got a Remy Gold alternator in a store brand box.
 
Unless all the rebuilt ones were done wrong, all the same way, you have a short or a very serious draw to load the alt that hard to be under that much charge all the time. New battery cables? Maybe start pulling fuses 1 at a time to see if you can find a circuit pulling a heavy load.
 
Glad you have the initial tests out of the way.

When the voltage is bouncing from 9 to 15 volts you are experiencing the condition that is killing the alternators. 9 is running on the battery. 15 is alternator working. So something is going "open" like a loose connection/bad cable or shorting the alternator output. I would suspect the fusible link on charge wire. Give it a wiggle test with a voltmeter on the battery. When you wiggle the wire and the voltage drops you found the issue. You also may see big sparks if it is a short. Wear eye protection! The batteries can explode if you have a short on the big cables.
 
I have found some battery cables look great on the outside but inside they are green dust and will not conduct current effectively. My friends burb went through 3 before he replaced all the cables with a big 3 upgrade and that fixed it for good. The big black negative was dust!! Thing is it rang out with a continuity tester but as soon as there was some load it would not work.
 
JMJNet said:
I would get a NEW (not rebuilt/refurb) alternator if buying from part stores.

If you want rebuilt, find a local shop and buy rebuilt from them, instead.

For a 2000, you can get a new AD244 alternator, if you have not done so.
They are rated at 140 amps or so.
This alt is in larger diameter casing.

IMHO.

I bought a new alternator from AZ dot com and it was sent directly from Remy.
So, I suspect, I got a Remy Gold alternator in a store brand box.
Click to expand...

I had a brand new 170 amp AD244 go bad after just two years. Lifetime warranty, but that's worthless when you're stranded and bought it on-line. Got a reman from NAPA with lifetime warranty.
 
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