Tonight my dash warning lights were staying on and my battery gauge was steadily falling, how can I test if it is my battery or alternator failing?


Steve

 

go by any parts store and they will test your **** for free.

 

That's my plan for tomorrow, but if someone knows an easy way to DIY I'd be grateful.

 

Highly likely it is the charging system, with the lights coming on. One way to test is to measure the voltage across the battery without the engine running and then after the engine has been running for awhile. If there is little change or the voltage goes down when running, prolly the charging system.

What year car? Does it have an integral voltage regulator in the alternator or separate?

 

As far as the DIY yourself stuff goes, the best method is the "replace stuff until it works" way, besides that for testing battery's and alternaters your pretty much SOL. But any car shop should be able to load test your battery, and check that your alternator output is good. I would rather do this method than the replace stuff until it works method, but im not rich...

 

remove the wire on the back of the alternator (bigger one that is normally held on with a 8mm nut...AND DONT LET IT TOUCH ANYTHING!) and start the car. check the post with a multimeter and see what its puttin out. most multimeters cant handle anything over 10 amps so voltage is the only thing youll be able to test......unless you have a load tester for the battery. if you got one, make sure the battery is charged up, connect the load tester and then push the button. it will let you know if the batterys recovery/reserve properties are worthy of your ride

oh, but it would be easy to go to a parts store and have them test it with their super duper equipment.

 

My immediate thought was the alternator, just thought I'd check I have a S4 alt ready to go so I'll do that change tonight and see hwo it ends up...thanks all

 

Yeah, parts store. The reason i suggest this is beacuse if you just do a voltage test on the back of the alt, and ya get say 13 volts sure thats fine. But its not under load. It needs to be tested under load.

So yah, just take it buy and get them to load test the batt..

 

If all dash lights were on usually means the alt took a dump.

 

Quick test is to remove the battery's terminal while the engine is running. Be sure to loosen the terminal prior to start and wrap it with a cloth or something.

 

Perhaps a dumb question but have you looked under the hood to verify you still have an alternator belt?

 

Thanks to one and all, I replaced my alt with an S4 alt, and all is good again. More lights also....

Blake, all suggestions are welcome, there are no dumb suggestions, I appreciate all input.