Replaced Battery

Just installed a new battery on my tundra. It is running fine but the battery light is on when in idle. When I give it gas it goes away and then comes back on when idle, however the battery gage remains in place when I give it gas. Why is the light still on?

 

Your alternator maybe failing

 

Was the light on before you replaced the battery ?

 

sounds like an alternator.

 

Yes the light was on before I changed the battery.

 

Put a voltmeter on the battery as the truck is running. If it’s not reading 13+ Volts it’s not charging.

This is the fastest way to test if it be alternator is working.

 

To me, this is a sign that the battery is failing. The battery light comes on at idle because at low rpm the alternator is putting out very little current so the ammeter (the battery light) is telling you that the battery is discharging. When your rpm increases, the light goes out because the alternator is putting out more current than your truck requires to run itself (spark plugs, electronics, etc.). I'd start with a battery replacement, but you can also have the local auto supply store test the battery for you before making that decision.

 

This.

 

I put a brand new battery in it and it is still showing up in idle and disappears with acceleration. Took it to a shop and the voltage read 11.7.

 

Assuming that voltage reading was done with the truck running the alternator needs to be replaced.

 

So you put 2 new batteries in it? Again, go test the voltage with the truck running and report back.

 

This forum is kind of crazy… the amount of new batteries bought here that are not needed is so high.

If it’s only making 11.7v at idle, I would test it again but this time rev the engine up to 2-3k rpm. If it starts to show voltage then you alternator is starting to fail.

It’s not charging at idle but when you rev it up, it’s spinning the alternator up enough to start kind of working. Reasons why the battery light goes off.

Most likely will be replacing an alternator which is not exactly cheap. Buy a good quality one, not a chain auto parts store one. You don’t want to be doing this all over again in a few months to a year

 

The trend to not diagnose and just fire up the old parts grenade is not waning. A little more diagnosis time will save you a lot of money in the future.

I agree-do not put a cheap alternator in. Go to a reputable online dealer and get the new OEM, about $300. You don't want the headache of having to do it again, it's kind of a pain to access.

 

If you don't have a voltmeter your local auto store (most) can check the charging system for free. Just to double check.