Hey guys,my sister's HHR was not cranking and we found out the alternator was bad. We replaced the alternator and was working fine until the 3rd day. The car wouldn't crank and found out it was the alternator again, confused. When taking out the new alt "refurbished btw" we noticed the 2 pin plug connected to the alternator did not power when we turned on the switch. We did test if the alt was not good by disconnecting the battery, once we did that the car did shut down. Now my question, where is the power coming from in the 2 pin plug, and or what could be causing the car to shut down after we replaced the alt after 3 days. btw the battery is used.

 

It could be a bum battery!

 

And disconnecting the battery while the vehicle is running can cause serious problems, expecially to the alternator.

 

It aint the sixties anymore. unhooking the battery on a modern car when it is running is a BIG no no.

 

to the forums!! Let's see if we can make this understandable for all.

The engine wouldn't crank, and you found out the alternator was bad. How did you determine the alternator was bad?

You replaced the alternator with a remanufactured one, only to have the 'no crank' condition return 3 days later. Again, you found out the 2nd alternator was bad. Same question, how did you 'find out'?

You then removed the alternator again, 'noticing' that the connector had no power when you turned on the switch. Exactly how did you perform this test?

Then you disconnected the battery in order to test the alternator, and the car shut down. Did you have the engine running without the alternator installed? What kind of test is that, what was the expectation?

The battery is used. As others have stated, it would be good to get the battery tested. See if the testing facility will give you a printout of the test results, post it up here.

Hopefully all the experience here can get this diagnosed and fixed up!!

 

The 2 pin plug is the control signal for the alternator. It turns it on and off in a PWM way. a VOM would not tell you anything.

How are you "finding out" it's a bad alternator, sounds more like a bad battery to me.

 

Your auto part palace can bench test the alternator and load test the battery, usually for free.

 

Like Oldblue said you should have the battery and alternator tested for free before you replace anything. If you replace an alternator you should always check the battery. A bad battery can kill an alternator. An alternator can burn up trying to charge a battery that won't hold a charge. When I have a dead battery I always try to charge it with a charger instead of jump starting a car. Using your alternator to recharge a battery is hard on it.

 

OP hasn't come back.

But. Power to the alternator comes from the starter which is straight from the battery.

 

This video tells how the alternator is excited, why an alternator won't work without the control circuit or a good battery.

H'mm that time it posted the vid, not just the url.