luistino

Jeep Grand Cherokee Laredo 4x4 3.6 2011

I am diagnosing a no charge situation after major alternator blow up. how can I verify new Alternator is operating correctly, Thanks

97grand4.0

bring it to autozone and have it bench tested

wingless

When my generator was suspect, I tested per the FSM, w/ a carbon pile load, an ammeter and a voltage meter. That testing worked great, as-shown in this topic.

luistino

will call see what they say.

luistino

thatsquite a test. looking for a easier way out

Bugout4x4

I must be a simple minded redneck... I just start it up and turn everything on, headlights, A/C on high, stereo cranked, Dome lights on, and see if the headlights are bright white as they should be. Then shut the engine off and see if the headlights dim substantially. If it goes very noticeable from bright white to dim yellow the alternator is working fine. If they are low and yellow with all this on while running and not much change when you shut it off, the alternator is not keeping up. lol

97grand4.0

They might not have a carbon pile tester but they do have a pretty snazzy one that uses microprocessors and predetermined voltage drops, which may have been invented after the FSM was written.

LOL Us real rednecks that had distributer and points and a carb would probably put it in and see if it ran the car with the battery unhooked. ( Dont do this!!)

Bugout4x4

Lol... Fact. Miss those days when you could borrow a battery from a donor car, start a second car up, then return that battery back to the original donor car.

"Can I borrow your battery for a minute because I don't have one? Give it right back after I start this"

dave1123

Hell, I knew a guy who drove his Chevy truck to a fishing spot, unloaded his canoe, took the battery out of the truck, put it on an electric trolling motor on the canoe, fished all day, put it back in the truck, started it and drove home! Now THAT'S a battery!

I also remember with those GM alternators, you could "full field" them by applying 12v to the field winding while the car was running and if the engine slowed down, the alternator was putting out full power.

Bugout4x4

I know you know this one Dave... Putting a field cut switch to get just a little more out of it for a street run.

dave1123

Oh yeah! And adding an electric fuel boost pump because the Quadrajet pulled so much fuel that the float bowl would go dry just about at the top of second gear! One guy I know built a fan hub that would allow the fan to just freewheel if you retracted a pin. That gave you around 20hp right there.

Bugout4x4

Holley double pumpers would do that too.

But now we are getting off topic... lol

dave1123

Getting back to the alternator test, I'm with you. Turn the headlights on then start the engine. If everything suddenly gets brighter, the alternator is working.

Bugout4x4

Simple logic. And it's free. lol

97grand4.0

I see the OP's point, changing out the alternator is no quick task, he wants to make sure he has a good one.