Quick Question?

[onthelake]

What does your guage show for your volts while you are running? I think I have a battery going bad. When I am running it shows 11.8 volts, but after running a while it gets down to 9.5 and a low battery alarm goes off. I switch over to my other battery and finished out the day. I am trying to figure out if it is alternator or battery? Thanks guys.

[Chia]

mine shows 14.4v

[GreenMan]

Definitely an alternator / charging system problem.

Almost regardless of battery condition, with the engine running the alternator should quickly lift the system voltage to around 14V. Your problem may be as simple as a slipping drive belt or a loose wire somewhere...

[REW]

What does your guage show for your volts while you are running? I think I have a battery going bad. When I am running it shows 11.8 volts, but after running a while it gets down to 9.5 and a low battery alarm goes off. I switch over to my other battery and finished out the day. I am trying to figure out if it is alternator or battery? Thanks guys.

While running the alternator should be putting out at least 13.5v I would be looking for more around 14 to 15. Dont get worried about the high side until it gets about 18. Check the condiction of the belt and pull the alternator off and have it checked under load if your battery charger wont do it for you. (most of the newer ones will). Based on your quick question it sounds like your batteries are strong, just not getting charged.

[tvzzz]

Unhook the battery while it is running, if it dies it is the alternator.

[skier92]

Start by checking wires on alt. Have seen the connector break off due to vibration. Also check belt tension.

[Michigan boarder]

A depleted battery, hooked to nothing when tested, will show 12 volts. So to test it simply put your meter on it and it should read 12 or more. Anything less, and you have at least 1 bad cell in the battery. The short in the battery could also be pulling down the alternator. Still, my guess is you have a bad alternator, based on the low voltage when running, otherwise a bad battery would not have enough power to start the engine.

[electricjohn]

Unhook the battery while it is running, if it dies it is the alternator.

Do not do this if you have a fuel injected engine. This can irreversibly damage the ECM.

[MalibuTime]

Unhook the battery while it is running, if it dies it is the alternator.

If you have a newer Malibu I don't think this is a good idea. Someone mentioned really effing up the engine when they did something like this, I think it was unhooking the battery while running. Might have been something else though. But will all of the electronics and control modules I would not be unhooking the battery under load of a running engine.

[onthelake]

Thanks guys. I am going to check the wires and connectors this afternoon when I get home. It is fuel injected, the

Indmar Monsoon 325hp. I hope I find a connector broke instead of it being the alternator.

[WakeGirl]

Get the battery tested to rule that part out first. Low voltage isn't necessarily indicative of a bad alternator, even given the symptoms. It could just be a bad battery. Don't ask me how I know that.

[Baddog]

Batteries are expensive but not that expensive. If you are doubting it just buy a new one and have peace of mind.